DIYstompboxes.com

I was looking around and discovered that, as far as I can tell, there are no tap tempo trem projects that have been put together. Seems like there should be. So let's make it happen.

Molten Voltage has a tap tempo LFO chip (http://www.moltenvoltage.com/mv-53.html). It's pricey compared to pretty much any other IC you're likely to find. However, it does a lot, and makes the external component count pretty small. They even have a tremolo schematic (http://www.moltenvoltage.com/downloads/MV-53_Tremolo_Schematic_v1.jpg) already done. However, the audio portion of this circuit is passive. It uses a part I haven't come across before, an optoisolator whose photosensitive part (which would normally be an LDR) is a bilateral switch. So it can only turn down the volume, there can't be any boost. It would, at the very least, need a gain stage at the end IMO.

Can we put together something better? Would the above schem with an opamp amplification stage after it have any drawbacks?

As with the Gristleizer, I'd be up to do a double-sided board layout and get the boards made up. But I don't have the dough to do a group order on the Molten Voltage chips to get a lower price, unfortunately. Still, I think $20's not too bad for what it does.

Burst Box!

Only problem is that you'd have to keep tapping for as long as you wanted the effect.

The MoltenVoltage site seems to be down at the moment.  You must have scared them, Taylor.

The main problem with the MV tap tempo chip is that the output is an analog voltage.  I know, I know, they tout it as a feature, but if the output was available in PWM or some digital format, you could simply hook up a CMOS analog switch IC and voila: there's your variable resistor.  Total parts count: 2 ICs and a switch.

Since it's a continuous voltage, you're forced to use one of the more standard voltage controlled resistor type circuits (JFET, MOSFET, LED/LDR), not one of which is simple, accurate, and repeatable.



My preference would be just to convert the LFO to PWM.  A high speed comparator and a fast, linear sawtooth oscillator would be required.  That would make a depth control easy (just a voltage divider between MV LFO and comparator).

Then your "variable resistor" would be a CMOS switch, or discrete transistor.

I wonder if square could be integrated to triangle and somehow make rise & fall times & amplitude adjustable

how would work if I take epfm super tone control and put larger value caps on it so it could "eq" that lo f perfect sine to not so perfect

Last summer I did build Musikding "Das Tremolo" with many knobs and it is difficult to get any ugly sound from it

Today or yesterday I googled simplish midi metronome done with pic or something, it would be nice if a trem could be synced to midi clock

I built a tremolo earlier this year based on the Tremulus Lune (link (http://www.diystompboxes.com/smfforum/index.php?topic=77471.0)), but using Tom from ElectricDruid.com's PIC-based VCLFO 9D (http://www.electricdruid.com/index.php?page=projects.lfo9). It's output is PWM, and works very well. The LFO is very flexible, easy to use (once burned on the PIC), and offers a wide variety of waveshapes that sound really good in my tremolo.

Tom was working on a tap-tempo version of the VCLFO, and even has a topic here about it (link (http://www.diystompboxes.com/smfforum/index.php?topic=76436)). I know he had a test version up and running, but I'm not sure if anything has come of it yet.

It may be a good option, though. If he finishes and releases the code, maybe you could design a circuit around his PIC. I know that not everyone has the tools to burn PICs, but if you did a group buy for a board for DIY use, you might be able to get permission to include ready-to-go LFO PICs with the boards.

Just a thought. :)

Mike

I had a thought.  Check out this mojohand thingie...  http://www.tonefactor.com/proddetail.php?prod=Ramp

It ramps between two speed settings, and it can be used to drive their flanger, vibrato and vibe.  My first though is that it contains an LFO that takes precedence over the LFO internal to the actual effects.

I think it would really cool to come up with some kind of universal LFO controller or tap tempo device that could be spliced into to any number of modulation effects that we could edit, why stop at tremolo?  Beat sync'd tremolo and delay is very very cool btw!

Maybe we could do Tap Tempo, as well as two speed settings that could be toggled/ramped between.  Design it the right way and you don't have to use all the features in the build necessarily, but the flexibility is nice.

Quote from: .Mike on November 20, 2009, 09:39:57 AM
I built a tremolo earlier this year based on the Tremulus Lune (link (http://www.diystompboxes.com/smfforum/index.php?topic=77471.0)), but using Tom from ElectricDruid.com's PIC-based VCLFO 9D (http://www.electricdruid.com/index.php?page=projects.lfo9). It's output is PWM, and works very well. The LFO is very flexible, easy to use (once burned on the PIC), and offers a wide variety of waveshapes that sound really good in my tremolo.

Tom was working on a tap-tempo version of the VCLFO, and even has a topic here about it (link (http://www.diystompboxes.com/smfforum/index.php?topic=76436)). I know he had a test version up and running, but I'm not sure if anything has come of it yet.

It may be a good option, though. If he finishes and releases the code, maybe you could design a circuit around his PIC. I know that not everyone has the tools to burn PICs, but if you did a group buy for a board for DIY use, you might be able to get permission to include ready-to-go LFO PICs with the boards.

Just a thought. :)

Mike

I have a standalone, analog tap-to-voltage converter that could be used with that:
http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/earthtonesgallery/PT2399_tap_tempo.png.html?g2_imageViewsIndex=1
Voltage output from IC1B, everything to the right of it is for converting the voltage to a current and could be omitted.
Obviously this is not as elegant as doing the tempo part digitally... but it doesn't require a clock.

Quote from: aziltz on November 20, 2009, 10:04:27 AM
I had a thought.  Check out this mojohand thingie...  http://www.tonefactor.com/proddetail.php?prod=Ramp

It ramps between two speed settings, and it can be used to drive their flanger, vibrato and vibe.  My first though is that it contains an LFO that takes precedence over the LFO internal to the actual effects.

I think it would really cool to come up with some kind of universal LFO controller or tap tempo device that could be spliced into to any number of modulation effects that we could edit, why stop at tremolo?  Beat sync'd tremolo and delay is very very cool btw!

Maybe we could do Tap Tempo, as well as two speed settings that could be toggled/ramped between.  Design it the right way and you don't have to use all the features in the build necessarily, but the flexibility is nice.

I've been thinking of something similar - having effects that sweep take a control voltage via a high impedance input (something like a FET controling the current into to the LEDs of LDR/LED pairs)  rather than having the LFO onboard.  In addition to syncing multiple effects from the same control voltage,  you could use the same effects with a envelope follower, sequencer, or expression pedal as well and swap in incrementally more feature rich LFOs without having to alter the primary effect.

I guess this post is my fault, cause I asked Taylor about a tap tremolo circuit.

Is it wrong to ask questions like "how does the empress unit and the Cusack unit and the Seymour Duncun unit do it?"

I detest Berhinger for their backwards engineering, but I also recognize that we could learn a lot for our own circuit by understanding those.

I know some people don't think tap tempo is helpful, but I want to build one, so nevermind it's helpfulness!

The EA is a tried and true trem, lots like it. Could we base off that and add a tap tempo circuit?

Quote from: jkokura on November 20, 2009, 12:15:45 PM
I guess this post is my fault, cause I asked Taylor about a tap tremolo circuit.

Is it wrong to ask questions like "how does the empress unit and the Cusack unit and the Seymour Duncun unit do it?"

They all have custom digital chips that they designed. Some of them may be digitally controlled but analog signal path, but some may be digital all the way through.

Quote from: Taylor on November 20, 2009, 01:51:27 PM
They all have custom digital chips that they designed. Some of them may be digitally controlled but analog signal path, but some may be digital all the way through.

So then the idea of starting from a common trem like the EA and then adding a digital tap tempo control is possible. It may not be the easiest solution.

I wonder, there's a PTAP for some common delay pedals, how did that come about? I know that circuit works with a micro-controller and digital pot which fits between the 'delay time' pot and it's connection to the board.

Would it then make sense to try and apply that MoltenVoltage circuit in that method (assuming the method hasn't been trademarked and we wouldn't be stealing...)

Just asking questions, I'm a true newbie when it comes to these things, been building for a few months and learning/researching effects circuits for maybe 8 months.

PTAP turns tap tempo into a resistance, which means you could use it with basically any of the analog effects which use a pot to set the delay time.

Quote from: jkokura on November 20, 2009, 03:22:04 PM

So then the idea of starting from a common trem like the EA and then adding a digital tap tempo control is possible.

Yep, that's definitely possible, but since much of the circuitry in most trems is for creating and shaping the LFO, we really only need the audio part, which is generally quite simple.

Earthtones, what's your objection to an optocoupler? I think an input buffer, followed by the LDR part of an opto like the NSL-32, into an output gain stage would be good and simple. Is there a problem with it? I know you're a major proponent of PWM, but to me using an opto is a well-proven way to make a nice trem. I guess the only drawback I see is that sometimes optical trems can't get really choppy with a square wave, since the opto smoothes out the waveform a little.

I like optocouplers, but they have several drawbacks:
LED brightness nonlinear
LDR response nonlinear and slow
Wide tolerance

Of course you can deal with all of these, but...
CdS cells were recently added to the RoHS blacklist by the EU, so analog optocouplers are probably going the way of germanium.   :'(

With PWM and CMOS or JFET switches, you trade all of those things for a high frequency clock.

Hey guys. If i may, let me make an offering.

I have a two PIC, tap controlled, LFO which outputs a 50% duty-cycle square wave that I use it for many applications. It uses a two-tap implementation with a range of 50ms-1000ms. Its been proprietary to my company for a while now, but i'd love to offer burned devices for this project. If there is enough interest, i will make a bulk purchase of the PICs, burn them, and ship them to all the contributors. I'm willing to go $10 on the whole system/ shipped.

Here is the momentary switch i use:

http://www.smallbearelec.com/Detail.bok?no=27

(One half is Normally Open, the other half is Normally Closed. The middle terminal is common to both. My chipset uses N.O.)

Here is the basic schematic:
(http://c1.ac-images.myspacecdn.com/images02/12/l_0951f1f14b4643acadb1e6a01b8a5b40.jpg)

This is very easy to add a depth and "shape" control (with an RC filter). I've used this to make an LDR trem like the Lune.

Quote from: earthtonesaudio on November 20, 2009, 04:31:33 PM
Of course you can deal with all of these, but...
CdS cells were recently added to the RoHS blacklist by the EU, so analog optocouplers are probably going the way of germanium.

LDRs are still being manufactured, even the infamous VTL5C1:
http://www.alliedelec.com/search/productdetail.aspx?SKU=9800700

with availability on Ebay, SmallBear, and who knows where else.

Let me know what you think!

One more note on clarity: the 10k pot shown is for the rate, same 55ms-1000ms range. You can use the tap or the pot at any time. I added the pot because nobody (that i know) can tap a 55ms tempo, so the pot lets you get at the vibe-like settings.

While I'm thinking about it, I need somewhere to read and understand LFO - I'm lost in some of the conversation here. If I'm not mistaken, it stands for Low Frequency Oscillation, but Taylor made me think I need to understand it better, cause I'm planning on mounting a Phase, Trem and Flanger all in one DD box, and he said something about making their LFO's match and I thought to myself, "I don't know what that means, but sure - especially if it's good for my sound.

If we can get a tap tempo mod from this that will apply to the trem, I'd love to get it so we can externally mount it (or I just have to think hard about where to mount the other switches for the phase and flange) and then add it to this project. If not, then I may just build a separate EA Trem with the tap function (or whatever trem we come up with here). Yes I will be posting pics of this build. I plan on making it freaking perfect, with a spiffy paint job and labeling, so I can enter it into any future contests (here and/or at BYOC).

Boy am I realizing how much I like this stuff, but that I feel like there's a mountain of info in front of me.

Quote from: jkokura on November 20, 2009, 05:22:18 PM
While I'm thinking about it, I need somewhere to read and understand LFO - I'm lost in some of the conversation here. If I'm not mistaken, it stands for Low Frequency Oscillation, but Taylor made me think I need to understand it better, cause I'm planning on mounting a Phase, Trem and Flanger all in one DD box, and he said something about making their LFO's match and I thought to myself, "I don't know what that means, but sure - especially if it's good for my sound.

According to my best understanding, a Low Frequency Oscillator is used in modulation effects to create a sweep. For example, a tremolo modulates volume from loud to soft. If you imagine a square wave, in terms of a tremolo, when the wave is high (or on, or however it would be described), the volume put out by the tremolo would be as loud as it goes. When the wave is low (or off, however it would be described), the volume put out by the tremolo would be as quiet as it gets. The LFO oscillates between high and low.

In other effects, like a phaser, the LFO modulates the phase shift. In regard to a delay, LFO modulation usually describes a slight raising or lowering of the pitch of the repeats, usually by slightly raising and then lowering of the delay time, which causes the repeats to sound, um, more spacial and, I suppose, liquidy-- kind of chorus-like.

You can use many shapes. Square waves, which are on-off, sine waves, which smoothly ramp up and back down again, "ramp up," which slowly ramps up and then quickly cuts off, "ramp-down," which quickly ramps up and the slowly cuts off, etc. Maybe this graphic (http://img44.imageshack.us/img44/4972/waveformshapesnoise.jpg) will help you visualize it a bit.

Syncing LFOs could open up a whole bunch of interesting combinations-- like a phaser whose sweep is in sync with the repeats of a delay, or a tremolo whose volume changes are in sync with the repeats of a delay. You could even us a ratio, so, for example, the sweep of a phaser could be twice as fast as the repeats of the delay, but still proportional. There are many possibilities.

Shifting gears, I emailed Tom from ElectricDruid to see if he's made any progress on his tap tempo VCLFO. I'll post here if I hear back. :)

Mike

The molten voltage chip might have scared people off by having lots of options, but I think if you cut those down (by not hooking up the crazy sequencer section), it would be rudimentary to hook up the molten voltage LFO chip to the signal path part of any existing analog tremolo design, just a matter of getting the amplitude and DC bias right, and then feeding that into the tremolo's gain control element (LED/LDR, FET, VCA).  Like take their odd passive tremolo, and shine the LED on the photocell in the signal path part of a tremulous lune, or run the LFO through a cap into the FET on an EA trem (or better, the rEAgenerated trem spinoff, with more depth).

I'll try to draw something up that fits the bill, I got a couple of their chips to experiment with, and an extra EA trem board I made for some reason.   That or a design using a modern VCA, like national's stereo voltage controlled level/pan/treble/bass chip, the LM1036.

Quote from: Processaurus on November 20, 2009, 10:22:42 PMLike take their odd passive tremolo, and shine the LED on the photocell in the signal path part of a tremulous lune,

That's basically what I had in mind, except I don't want to yoink the Lune directly - I'm not sure it would be ok to make and sell PCBs of Dann Green's design, even modified.

Quote from: rustypinto on November 20, 2009, 04:53:15 PM
...but i'd love to offer burned devices for this project. If there is enough interest, i will make a bulk purchase of the PICs, burn them, and ship them to all the contributors. I'm willing to go $10 on the whole system/ shipped.

... and competition drives the cost of a tap-tempo PIC down by half!  :icon_biggrin:

Quote from: R.G. on November 21, 2009, 10:52:43 AM

Quote from: rustypinto on November 20, 2009, 04:53:15 PM
...but i'd love to offer burned devices for this project. If there is enough interest, i will make a bulk purchase of the PICs, burn them, and ship them to all the contributors. I'm willing to go $10 on the whole system/ shipped.

... and competition drives the cost of a tap-tempo PIC down by half!  :icon_biggrin:

Ha, i was really just throwing that price out there, mainly to cover shipping and the devices. i'm not at all in the pre-programmed device market. My chip set doesn't have quite the wave-form features, but it does make a very nice LDR trem with shape/rate/depth and tap.

I've noticed that the square wave modes on the Gristleizer stay really choppy even at fast speeds. Maybe a FET would be a good way to go here?

Hey guys,

Just to follow up on my first comment in this topic, I heard back from Tom from ElectricDruid about his progress on his tap-tempo chip. Here's some of what he said:

QuoteWell, I've done quite a bit to it. I've got a working version of the VCLFO with tap tempo. There are one or two things still to do, like improve the accuracy of the tempo measurement (currently it measures milliseconds) and make it so that you can set the frequency using either the tap tempo or the frequency knob/CV. Currently it is tap-only for testing.
I made one or two changes from the VCLFO version following comments made on the forum I started about it. I altered the waveform selection for a more 'effects friendly' collection, so it now has Ramp up, Ramp down, variable-width pulse/square wave, Triangle, Sine, Sweep wave (the lower half of a sine wave), Lumps wave (the top half of a sinewave), and Random (the classic sample-and-hold random levels).
It also has a "tap tempo multiplier" control which allows you to set the frequency at a multiple of the tempo you set. The are currently 16 options for this, including whole note, half note, up to 1/32nd note and also dotted notes and triplets from wholenote triplets to 1/16th note triplets. I suspect this is too complicated and I might reduce it to the eight most useful options (like the waveform control, which could also easily have more options).
I'll probably publish the code once I'm done so people would be free to make custom versions with more/different waveforms for their own use.

This really might turn out to be a good option for a project like this, and other future projects. I don't mean to knock the folks who make similar chips as these, but it might be more in the spirit of DIY to use a chip with more open, modifiable code than purchasing a locked-down, unchangeable commercial chip. Once the programmer is purchased, the PICs are very cheap.

Anyway, just wanted to give an update in case anyone was interested. :)

Mike

Sounds cool, openness is excellent, but for me the main thing is to make this accessible to everybody. If somebody was into programming and selling and shipping the PICs for a reasonable price, that would be great. I just want to make this a simple project for people who have no understanding of digital tech. There shouldn't be the need for folks to program their own parts, etc. (though the option to do that is great for guys who are familiar with it).

Quote from: Taylor on November 21, 2009, 02:35:57 PM
Sounds cool, openness is excellent, but for me the main thing is to make this accessible to everybody. If somebody was into programming and selling and shipping the PICs for a reasonable price, that would be great. I just want to make this a simple project for people who have no understanding of digital tech. There shouldn't be the need for folks to program their own parts, etc. (though the option to do that is great for guys who are familiar with it).

And it's this kind of idea that makes me interested, cause I'm so new at this half this conversation goes over my head!

I really like this kind of open idea is kinda like the PTAP, as in it's a community or a person who create, sell and ship a kit and you can add it to a few projects that it works with. Perhaps this turns into a kit, or at least we come up with a guide for a mod anyone can do using a commercial chip, but isn't part of this that we should come up with a Tremolo we want it to work off of? Perhaps this is presumptuous or preemptive, or perhaps you've already all assumed these kinds of features in this trem, but here are some of the features I'd like this kind of trem to include:

- The ability to choose between a few different wave forms (sine, triangle, square)
- Controls for depth, level (fix any volume drop when turned on from true bypass), and rate/speed (that last would be able to be modded to include the tap function)
- Fit it all in a BB size box
- 9V power
- An LED to give us the speed both when using the knob or with the tap function be a good idea
- I'd like a method for being able to bypass the tap tempo function (tap once for on, hold for 2 second to turn it back to Knob control?)

Questions I'd have:
- For that matter, can we control the tap function even if the effect is bypassed? As in, while I'm playing the verse and expecting to turn the Trem on for a chorus of a song can I be tapping it in so it's already at the right tempo before I turn it on.
- When tap tempo is engaged, what would the rate/speed knob do then?
- Ramp up or down feature? My vote is no - that's starting to emulate the 'commercial' offerings too much for me, and I'd rather build a leslie simulator for that kind of effect.
- Could this tap tempo project end up being used in some other modulating effects? (Vibe, phase, flange, etc.)

Jacob

I'd love to see both possibilities come to fruition. Right now I'm not capable of burning my own chips (except in the oven  ;D) but in a few years, who knows, and there are already quite a few projects on-the-go in this forum using programable chips, seems like the trend is set to continue. Maybe one of the forum sections will end up being "Code"
I appreciate what Taylor is saying however, in terms of numbers, the more accessible, the cheaper any eventual PCB prices will be.
Shame not to be able to utilize some free code though, if only we knew someone willing to program chips for us .....

I believe I posted the overall programming approach to do a tap tempo program here a few years ago. This really isn't any big issue if you've done any microcontroller programming.

Here's an interesting issue though. Let's say that tap tempo was trivial, and that there was a $20 part you could just buy that did it. Do you really want a tap tempo *tremolo*?

Tap tempo makes sense for a delay, because the audible delay always starts when you hit a note. The echo happens one delay time later. Even if you make tiny errors in setting the delay, the error is constant per note because the delay only starts for that note when the note happens.

However, there is always some error in setting a tempo. There exist people who are dead-accurate in tapping a tempo, I suspect. I'm not all that great at it, and I suspect there are many who are as bad as I am or worse. Otherwise, there would be no need for metronomes or click tracks.

If the tap tempo sensing algorithm inside your tapper was *perfect*, it would be very confused when your successive taps to set the tempo were not all at the same time apart. This is why good tap sensor routines take several taps and average or otherwise try to figure out what tempo the silly, no-rhythm human was trying to do. And it's good at this, comes up with something that is least-squared, triple polynomial regression of what you actually tapped into the machine.

What are the chances that what you tapped into the machine is what the drummer is going to beat? It's unlikely - unless your drummers are much better and more willing to please than mine ever were! Mine always expected me to follow them, not the other way round.  :icon_lol:

But let's say you're really practiced and you (and your drummer) manage to start playing a beat that's only 0.5% different from what the tap tempo chip thought you wanted.  Ten beats later the tempo in the pedal is off by 5%. A hundred beats (maybe 10-20 measures) into the song, it's 50% off and now the silent part of the sound is on top of the beat, not after it. The tremolo is now 180 degrees out of phase with your playing.

Notice that the problem is one of the machine not following your playing and the error building up. This cannot happen with delays, as the error is always 1X, not once per beat.

So ask yourself... do you feel lucky?   :icon_lol:

good drummers would play to the tremolo.

Would it be more accurate if you tap Quarter notes and use some kind of subdivision setting for faster stuff?

Quote from: R.G. on November 21, 2009, 04:39:57 PM
Here's an interesting issue though. Let's say that tap tempo was trivial, and that there was a $20 part you could just buy that did it. Do you really want a tap tempo *tremolo*?

Tap tempo makes sense for a delay, because the audible delay always starts when you hit a note. The echo happens one delay time later. Even if you make tiny errors in setting the delay, the error is constant per note because the delay only starts for that note when the note happens.

Yes, I do want a tap tempo tremolo. You make a good point that it will obviously go out of sync with the rhythm of the song, but that's ok with me. It's not about having it match up permenantly for a long time, it's about it's relative speed.

For instance, I do use trem in several recordings I've made. When I've played those songs live, I invariable have to reach down and tweak my trem so that it matches with the original sound/feel of the song. I don't have one trem speed setting that appears in all my music, and especially when I'm doing cover work that I use a trem in, it's impossible to reach down and change the speed of the trem every time.

However, with a tap function, I could do that all while standing and not having to worry about reaching down and adjusting a knob on the fly. Moreover, for those short sections of a song (i.e. a bridge, or a chorus) I'm good enough to tap in a tempo so that for that part my trem will match my bands tempo long enough for me to be ok with the slight out of sync that will show up 18 or 24 bars along in my songs.

So in short - you have a point RG, and by all means I'd understand if you disagree, but as a live musician I can see how tap tempo would really be advantageous (and fun).

I agree with RG in theory, but my experience is that this is only a problem when the band is playing to a click or the drums are programmed, etc. As long as you're playing with live musicians, they will tend to keep in time with the tremolo. The trem almost acts like a metronome.

As for programming chips, I guess it's not that complicated or expensive. I'm actually getting into DSP right now, so it may be good for me to get the skill of burning PICs and the like anyway. So maybe I'll burn the chips and sell them along with the PCBs.

Great, Taylor, I don't know how you find the time for all this, but I'm glad you are making the effort. I feel a series of tap tempo pedals coming on ....

edit: Oops, nothing.

Quote from: jkokura on November 21, 2009, 05:06:04 PM
However, with a tap function, I could do that all while standing and not having to worry about reaching down and adjusting a knob on the fly. Moreover, for those short sections of a song (i.e. a bridge, or a chorus) I'm good enough to tap in a tempo so that for that part my trem will match my bands tempo long enough for me to be ok with the slight out of sync that will show up 18 or 24 bars along in my songs.

So in short - you have a point RG, and by all means I'd understand if you disagree, but as a live musician I can see how tap tempo would really be advantageous (and fun).

That is a good reason to want it, OK.

Quote from: Taylor on November 21, 2009, 05:42:30 PM
As for programming chips, I guess it's not that complicated or expensive. I'm actually getting into DSP right now, so it may be good for me to get the skill of burning PICs and the like anyway. So maybe I'll burn the chips and sell them along with the PCBs.

It is almost trivial to set up to burn PICs. By far the biggest effort is the mental discipline to do the programming.

Wow. I'm a super newbie, 'arguing' with one of the giants around here, and he agreed with my point. I don't know whether to laugh at my foolishness or feel satisfied.

I doubt I'd ever build a tap tempo trem, but I do have an idea to fight the Russian Dragon (rushing or dragging - get it?).

The tempo is set at the start of the song, it's going to be a hassle to tap it in again at regular intervals during the song, and would certainly interfere with your playing. So what about a reset function on a momentary footswitch which wouldn't redefine the tempo, but would at least put the tremolo back on the beat. You could tap it once every so often just to tweak back in.

...world needz Tap-Tempo triggered by drummerz (as Mark knowz  :icon_wink: )

Quote from: puretube on November 22, 2009, 05:52:03 AM
...world needz Tap-Tempo triggered by drummerz (as Mark knowz  :icon_wink: )

Now that is a cool idea--maybe a hi-hat or kick-drum mounted sensor that you could read with a momentary stomper to set the LFO tempo.

Quote from: frequencycentral on November 22, 2009, 05:17:39 AM
I doubt I'd ever build a tap tempo trem, but I do have an idea to fight the Russian Dragon (rushing or dragging - get it?).

The tempo is set at the start of the song, it's going to be a hassle to tap it in again at regular intervals during the song, and would certainly interfere with your playing. So what about a reset function on a momentary footswitch which wouldn't redefine the tempo, but would at least put the tremolo back on the beat. You could tap it once every so often just to tweak back in.

my line 6 pedals work to this effect.  tap and play, and if it gets off, just tap some more.  Nothing stops or stutters, it just re-averages the tap time.  I know they're digital effects, but maybe we could apply that feature somehow.

Quote from: aziltz on November 22, 2009, 10:44:12 AM

Quote from: frequencycentral on November 22, 2009, 05:17:39 AM
I doubt I'd ever build a tap tempo trem, but I do have an idea to fight the Russian Dragon (rushing or dragging - get it?).

The tempo is set at the start of the song, it's going to be a hassle to tap it in again at regular intervals during the song, and would certainly interfere with your playing. So what about a reset function on a momentary footswitch which wouldn't redefine the tempo, but would at least put the tremolo back on the beat. You could tap it once every so often just to tweak back in.

my line 6 pedals work to this effect.  tap and play, and if it gets off, just tap some more.  Nothing stops or stutters, it just re-averages the tap time.  I know they're digital effects, but maybe we could apply that feature somehow.

This has always been essential to me for any tap effect. I use a lot of tap delays and (as someone else mentioned) after a while the band just treats it as a metronome on those songs where it needs to sync up. This usually works great but we can get sloppy at times and it helps to be able to tap in a few beats to re sync with everyone else. So there's my $.02:

A robust tap tempo tempo chip will average in new changes to the current clock speed.

btw... My hat's off to the digitally inclined people for taking this on.

Just a note to say that I'm close to finishing my PIC 16F684-based Tap Tempo LFO chip. The final version of the chip produces eight waveforms, and can output a frequency at a multiple of the tempo ( x0.5, x1, x1.5, x2, x3, x4).

I've just got some tweaks to finish off (like getting the Tempo knob and the Tap Tempo input to work together nicely) and then I'm done. I'll post code and a datasheet on my website when it's ready.

I'm thinking of getting a tubeful of chips programmed up, so there'll probably be programmed chips available for people who aren't into PICs.

Thanks,
Tom

That'd be great Tom.

So to be clear - does your circuit involve a specific trem or could this work with a variety of trem circuits (trem lune, Kay, ea...) Will you be posting a project file with trem and tap layout and offering to sell the preprogrammed chips, or is this going to be an tap tempo add-on that people can include as they design a circuit?

Jacob

Jacob,

No, this chip doesn't involve a specific tremolo, or necessarily any tremolo at all. It is purely a Tap Tempo LFO, so it could be used to give a tap tempo feature to most circuits that use LFOs. Tremolos are one example, but a tap tempo flanger sounds good to me, or tap tempo chorus, or panning, or etc. etc...you get the idea. Use it wherever you usually use the standard op-amp integrator triangle wave LFO!
I'll put some application circuits in the datasheet, but you could easily use it to drive a vactrol (or homemade LED/LDR combo). This would give you a tap-tempo LFO-controlled variable resistance, which is useful in many circuits. Alternatively, you can get the output as a straightforward LFO voltage output, which might be what other circuits require.
I'm not going to be doing a Tap Tempo Tremolo circuit myself, but  Mike's already done one with my PIC-based VCLFO, and the new Tap Tempo LFO would be a simple replacement. His work is here:
http://www.diystompboxes.com/smfforum/index.php?topic=77471.0

Like I said, I'm hoping to get a tube of chips programmed up, and if anyone was getting a run of boards together, I'd be more than happy to supply a batch of chips for a project. Watch this space.

Thanks,
Tom

Is it possible to add a tiny slope to the square wave, so that it sounds like a square but alleviates the ticking problem that so many LFOs suffer from?

Taylor,

Yeah, it's possible. The square wave is generated from a PWM pulse train (PWM DAC) by running it through a filter to recover the average analogue level. So you can smooth the square wave by adding another filter, or by tweaking the one that is there. However, there are many possible causes of ticking, and very sharp edges on the square wave is only one of them. It's possible that the schmitt trigger switching in a typical op-amp LFO causes a voltage spike which could be heard as a tick. That's one problem that this LFO won't suffer from.

Mike might be able to advise us here, since he built a Tremolo with the original PIC VCLFO. I don't remember him saying anything about ticking.

In short, you're right to be cautious, but unless we've got an actual circuit and layout, it's pretty hard to work out ahead of time where the problems will come from. I haven't had any such problem, but I guess your mileage may vary. Please recognise that this is an entirely different design of LFO to most, and so is likely to throw up an entirely different set of 'unexpected features'!

Thanks,
Tom

Adequate IC bypassing, careful layout and physical isolation help alleviate ticking. Also some high-pass filtering on the output (something like a 2nd order Sallen-Key filter) at about 30 Hz will usually do without killing your tone.

Thanks for the offer of programmed chips Tom. I would definitely be interested in one, perhaps a few, dependent on price. This sounds like a n interesting and flexible addition to a lot of circuits. I'm not set up to program as yet, I guess I'm not the only one, so I was kind of hoping you might step in and help us out.

Thanks to Taylor too, for starting this ball rolling.

I too would be interested in chips, depending on price.

Okey dokey, I think I've finished. I've put details of my Tap Tempo LFO up online at:

http://www.electricdruid.com/index.php?page=projects.taplfo

There are example circuit diagrams, a datasheet, code, etc. Any questions, please ask.

I'll be trying to sort chips out soon, and if I can persuade Steve Daniels that this is a good idea, you might be able to buy programmed chips from Small Bear.

Thanks,
Tom

That's a wonderful idea to have the available from steve - that way you don't have to deal with the ordering and mailing process but once, and you still reap the benefits (I'd hope).

I'd buy at least one, perhaps more.

Now the question is, what Trem is this going to work with - does someone think they could design one, or does this drop nicely into some pre-established trems?

Tom, other than a trem, what circuits (specific ones) would you want to try this with?

I'm still up to design a circuit and PCB for this. Should be pretty simple, just need to decide what kind of control element we should use. Tom has a schem for an optical trem using the tap tempo chip on his page.

http://www.electricdruid.com/images/lfo/TapTremolo.gif

Opticals aren't my favorite trems just because they can't get really choppy at high speed square waves, but for most guitar applications, they sound great. What say you all to an optical tap tempo trem? I can start on the PCB design today if everybody thinks optical's the way to go.

What other control elements could we successfully use with this doodad. I don't know all the pro's and con's of the different possibilities in terms of musicality in the end result. Anybody care to enlighten me, in broad terms.

If you're thinking of doing a PCB layout, please be aware that I adapted Mike's circuit diagram for the new tap tempo LFO. Whilst the LFO should be a drop-in replacement, he used a homemade LED/LDR combo, so there might be some tweaks for a given vactrol. I put a VTL5C3 on the schem 'cos that's what I've got in the drawer, but I haven't done the tweaks yet.

The vactrol has the advantage of acting as the PWM filter too, because of the slow response you mentioned. This makes the circuit nice and simple. Other types of VCA will need the op-amp filter stages shown in the other example circuit, which adds more components.

T.

Great work, Tom. I can't wait to try this. It's so generous of you to go through all the effort to make this for the community.

Just a few notes on the app note circuit that I "designed." I didn't really design anything. It's basically the audio path of the Trem Lune with the LFO replaced by the VCLFO. It works great.

If anyone is wondering about the transistor driving the LEDs, I used that because the PIC is limited at 20mA of PWM current output. So, if you were running two LEDs at full blast, you would be overloading the PIC output. I ended up with some popping when running the LEDs at such high current, so I reduced the current down to something like 3-4 mA. In that case, I'm sure you could omit the transistor that is acting as a current source, and just run the LEDs in parallel right off the PIC.

Taylor, I'm wondering if this will do the choppy square wave like you mentioned, at least a bit better than the standard LED/LDR tremolo. I am able to get a very good chop on mine by setting the waveform to square, and then using the wave distort to alter the on/off time of the LED. Basically, make the dark period much longer than the light period so there was more recovery time allowance for the LDR to catch up. On mine (using the original VCLFO9D), I can get it very choppy. The more choppy I let it get, however, the more gain I need to add to compensate for volume losses. Still, it works pretty good, and I would be happy to make a sound sample for you.

:)

Mike

Hmm, that sounds good, I had considered something like that. I admit I haven't had the time to really read up on all the capabilities and controls of this chip, but I have in other designs used a shorter "on" period to create a choppier wave.

I'd love to hear some sound clips if you have that capability.

The only thing that's worth some pause is that I don't know the legal/ethical/licensing issues with using a snippet of the Trem Lune to make PCBs. I could run it by Dann Green, though. I don't want to step on any toes, but at the same time I don't know that I could afford a licensing fee. Does anyone know the provenance of the Trem Lune's design? Is it from a manufacturer's app note by chance? I guess it's pretty much exactly what anyone would come up with when using an optocoupler to create series resistance, but I'm never sure how much ownership people can claim of ideas like that, and again I've always liked Dann, so I don't want to be disrespectful.

Quote from: ElectricDruid on December 08, 2009, 06:35:03 AM
Okey dokey, I think I've finished. I've put details of my Tap Tempo LFO up online at:

http://www.electricdruid.com/index.php?page=projects.taplfo

There are example circuit diagrams, a datasheet, code, etc. Any questions, please ask.

I'll be trying to sort chips out soon, and if I can persuade Steve Daniels that this is a good idea, you might be able to buy programmed chips from Small Bear.

Thanks,
Tom

I would definitely buy a couple if you offered pre programmed PICs. I'm sure there's quite a few of us here that would love to give this a try but aren't set up for PIC programming.

Quote from: Taylor on December 08, 2009, 06:59:32 PM
The only thing that's worth some pause is that I don't know the legal/ethical/licensing issues with using a snippet of the Trem Lune to make PCBs. I could run it by Dann Green, though. I don't want to step on any toes, but at the same time I don't know that I could afford a licensing fee. Does anyone know the provenance of the Trem Lune's design? Is it from a manufacturer's app note by chance? I guess it's pretty much exactly what anyone would come up with when using an optocoupler to create series resistance, but I'm never sure how much ownership people can claim of ideas like that, and again I've always liked Dann, so I don't want to be disrespectful.

This sounds like a great project! Of course I don't mind anyone using a series-resistance photocell circuit for a tremolo effect-- as long as no one minds me making my own tap-tempo devices! I've developed a tap tempo on a curious little bass synth project, using an AVR chip with code written in C:
http://4ms.org/projects/?p=49

It has a similar tap tempo subroutine (measure time between taps, ramp a PWM output to get an analogue output, which drives an LED, which shines on a photocell, which controls a resonant analogue filter), but it only does triangle wave. An interesting feature is a mode where you can tap a complex tempo (daaahh dit dit daaahh dit dit) and it will play that rhythm.... Tom, I'd be happy to help unearth that section of the code if you (or any coders) are interested. Basically, instead of keeping track of time as a single variable (FREQ_INC) I use an array of values for tempo, and the code steps to the next element in the tempo array each time it completes a waveform.

HTH :icon_mrgreen:

Awesome! Dann, you're a cool guy as always. I was checking out that Autonomous Bassline the other day and it's extremely neat and clever - especially the IR communication between circuits. And this is coming from a bass player - soon to be obsolete.  :icon_wink:

QuoteIt has a similar tap tempo subroutine (measure time between taps, ramp a PWM output to get an analogue output, which drives an LED, which shines on a photocell, which controls a resonant analogue filter), but it only does triangle wave. An interesting feature is a mode where you can tap a complex tempo (daaahh dit dit daaahh dit dit) and it will play that rhythm.... Tom, I'd be happy to help unearth that section of the code if you (or any coders) are interested. Basically, instead of keeping track of time as a single variable (FREQ_INC) I use an array of values for tempo, and the code steps to the next element in the tempo array each time it completes a waveform.

This is very intriguing...

Quote from: Taylor on December 09, 2009, 02:34:04 PM
Awesome! Dann, you're a cool guy as always. I was checking out that Autonomous Bassline the other day and it's extremely neat and clever - especially the IR communication between circuits. And this is coming from a bass player - soon to be obsolete.  :icon_wink:

QuoteIt has a similar tap tempo subroutine (measure time between taps, ramp a PWM output to get an analogue output, which drives an LED, which shines on a photocell, which controls a resonant analogue filter), but it only does triangle wave. An interesting feature is a mode where you can tap a complex tempo (daaahh dit dit daaahh dit dit) and it will play that rhythm.... Tom, I'd be happy to help unearth that section of the code if you (or any coders) are interested. Basically, instead of keeping track of time as a single variable (FREQ_INC) I use an array of values for tempo, and the code steps to the next element in the tempo array each time it completes a waveform.

This is very intriguing...

Most interesting if it were a switchable option, like in one mode we could get a patterned tap to influence the speed, but if we could also have an option where we could use the switch to measure the time between 3 taps to get the speed of the trem (or whatever LFO).

I like the potential of Tom's chip a lot though. I'd love to see what other kinds of implementation we can come up with down the road. Taylor, are you making progress on a circuit? Is this an add-on type feature like the PTAP, or is this an integrated feature (you can't seperate the tap function from the tremolo)? With my very limited knowledge, resources and skills, is there any way I can help out at all?

Jacob

Well, I'll probably do a PCB based on the above trem schematic now that we have Dann's approval. There is the question of whether we should wait to see if the complex tempo thing Dann suggested makes its way into Tom's chip. Its inclusion may make no difference to the actual layout, but if it adds an extra switch or any other physical components it would need to be accounted for in the PCB. What do you think about this, Tom? Do you plan to integrate it? Would it add any components or could this be done with the current controls?

The PCB I'll do would just be a tap tempo trem, but it could have an LFO output to control other things. The difficulty is that, the more you try to make a PCB work for a number of different applications, the more complex it becomes to build. People have to really know the circuit to know what parts to leave off, etc.

I could do a board just for the tap tempo, which could then be interfaced into any other circuit, but I personally really dislike having multiple boards for different sections of a circuit. Just my preference, though.

So then do a tap tempo trem PCB - seems to be the better option as far as you're concerned. If people want tap tempo add on perhaps someone will develop that, same with a tap tempo flanger, or phaser, or whatever else uses LFO... Vibe? Reverb?

So then my question becomes, what are the features for the trem you're going to use? Stock Tremulus lune? Are you going to give us a really basic trem with just a couple knobs? What do you see it looking like?

Sorry if I'm being nosey...

jacob

You may want to bring out the extra unused pins on the PIC chip to a header anyways, for further expandability (e.g. code v2.0 could interface with these pins, but the current code doesn't need to be modified to accomodate them)

Quote from: jkokura on December 09, 2009, 06:27:54 PM
So then do a tap tempo trem PCB - seems to be the better option as far as you're concerned. If people want tap tempo add on perhaps someone will develop that, same with a tap tempo flanger, or phaser, or whatever else uses LFO... Vibe? Reverb?

So then my question becomes, what are the features for the trem you're going to use? Stock Tremulus lune? Are you going to give us a really basic trem with just a couple knobs? What do you see it looking like?

Sorry if I'm being nosey...

jacob

ElectricDruid's post has a schem:

http://www.electricdruid.com/index.php?page=projects.taplfo

It's pretty much the audio section of the Tremulous Lune (just a couple of Opamp buffers and an LDR). I was under the impression that ElectricDruid was programming PICs which would be Tap Temp LFO's which would then control an LED which would in turn control the LDR in the audio path of the Tremulous Lune. If this is the case it would be a completely different LFO section from the Tremulous Lune. Unless I'm missing something in which case ignore me.  ;)

No, not nosey at all, the point is to have the features people want.

Tom's chip has lots of complexity built in. I recommend checking out his links on the last page to see all it can do. This chip allows for lots of really interesting things to be done, moreso than any other DIY trem I'm aware of. There's a larger variety of waveforms, and it allows to multiply your taps, so you can get triplet rhythms, etc.

Although we're using the audio section of the Trem Lune, it won't really share any of the controls with that, because all of the controls are in the LFO, which has been replaced.

This tap tempo trem will have the following knobs:

Tempo
Waveform
Multiplier
Depth
Output gain

Which covers all the functions of other tremolos plus much more.

I don't see the "Wave distort" that Mike mentioned, either in the tremolo schematic or the datasheet. Was that option excised? I think if we don't have that option, we could add a pot to control the voltage into pin 9 to get something like a "symmetry" control, aka pulse width.

Anything else you'd like to see in this PCB?

Edit: Ian beat me to the punch, and he pretty much got it.

Quote from: Taylor on December 09, 2009, 06:53:04 PM
I don't see the "Wave distort" that Mike mentioned, either in the tremolo schematic or the datasheet. Was that option excised? I think if we don't have that option, we could add a pot to control the voltage into pin 9 to get something like a "symmetry" control, aka pulse width.

Yeah, now that I look at the tap TAPLFO, it doesn't have the wave distort. Darn-- I really liked what that did.

From page 2...

Quote from: jkokura on November 21, 2009, 03:27:27 PM
- The ability to choose between a few different wave forms (sine, triangle, square)
- Controls for depth, level (fix any volume drop when turned on from true bypass), and rate/speed (that last would be able to be modded to include the tap function)
- Fit it all in a BB size box
- 9V power
- An LED to give us the speed both when using the knob or with the tap function be a good idea
- I'd like a method for being able to bypass the tap tempo function (tap once for on, hold for 2 second to turn it back to Knob control?)

Questions I'd have:
- For that matter, can we control the tap function even if the effect is bypassed? As in, while I'm playing the verse and expecting to turn the Trem on for a chorus of a song can I be tapping it in so it's already at the right tempo before I turn it on.
- When tap tempo is engaged, what would the rate/speed knob do then?

What about some of those questions?

The 5 controls you list Taylor are all the knobs I'd like - pots for depth, rate/speed and level; rotary switches from waveform and rhythm/multiplier (1/16, 1/8, dotted 1/8, 1/4, 1/2, 1/1 notes? some or all of those?).

But what I'm more curious is how the tap switch itself will be used - is it always on? does the pot override the tap switch? Do you have to tap or hold the momentary stomp switch to turn the tap function on? Can you tap out a tempo that will be established in the pedal before engaging the effect? Will there be an LED flashing to indicate current tempo?

I'm going to go look further into Tom's documentation to see if I can answer these questions, but if you have them already...

Jacob

Actually, now that I look at it again, I'm unclear. I *think* Wave Distort CV might be included, just renamed Pulse Width CV (pin 8). I looked through the code and it seems similar with just the variable renamed, but I'm not sure. Maybe Tom can clear it up (please)?

If that is the wave distort, I would definitely include it as an external control. If you take a look at the topic I made for the regular VCLFO tremolo that I put together, I posted some screenshots of what the wave distort control does, and some audio samples of what it does. In fact, Taylor, I already recorded a square wave demo, and it's there. It's not a particularly fast rate, though, so I'll record another one when I get time.

jkokura, from what I gathered, if you tap a tempo, even when bypassed, it registers the tempo UNTIL you touch the rate knob, which overrides the tapped tempo. As for LEDs, the circuit I put together has a status LED that is always functioning. If you use a transistor to provide the current for the LED, you can use as much current as your transistor can handle and run as many LEDs as you want. If you run the LEDs right off the PIC, you are limited in current by the output of the PIC, which is 20mA, I believe.

:)

Mike

Quote from: jkokura on December 09, 2009, 07:26:45 PM
- The ability to choose between a few different wave forms (sine, triangle, square)

The chip has 8 different waveforms.

Quote- Controls for depth, level (fix any volume drop when turned on from true bypass), and rate/speed (that last would be able to be modded to include the tap function)

Yep, we've got that.

Quote- Fit it all in a BB size box

Should be doable.

Quote- 9V power

Of course.

Quote- An LED to give us the speed both when using the knob or with the tap function be a good idea

Yep, should be doable.

Quote- I'd like a method for being able to bypass the tap tempo function (tap once for on, hold for 2 second to turn it back to Knob control?)

See here]=http://www.diystompboxes.com/smfforum/index.php?topic=76436.msg667635#msg667635]here (http://=http://www.diystompboxes.com/smfforum/index.php?topic=76436.msg667635#msg667635) to get a sense for how the knob and taps work together. Basically operating the knob overrides the taps instantly and vice versa.

QuoteQuestions I'd have:
- For that matter, can we control the tap function even if the effect is bypassed? As in, while I'm playing the verse and expecting to turn the Trem on for a chorus of a song can I be tapping it in so it's already at the right tempo before I turn it on.

Yes, the bypass will be purely mechanical with a 3PDT like usual, and the taps will be a separate stomp switch, so you can tap out tempos while bypassed if you want - the chip doesn't know whether the effect is bypassed or not.

Quote- When tap tempo is engaged, what would the rate/speed knob do then?

See above. The knob overrides the tap setting.

QuoteDo you have to tap or hold the momentary stomp switch to turn the tap function on? Can you tap out a tempo that will be established in the pedal before engaging the effect? Will there be an LED flashing to indicate current tempo?

Flashing LED, yes. I don't think there's any need to hold the tap switch, though I am a little unclear about whether the chip will average more than 2 taps or restart the tempo every 2 taps. Maybe Tom can explain that further?

Quote from: .Mike on December 09, 2009, 07:35:11 PMAs for LEDs, the circuit I put together has a status LED that is always functioning. If you use a transistor to provide the current for the LED, you can use as much current as your transistor can handle and run as many LEDs as you want. If you run the LEDs right off the PIC, you are limited in current by the output of the PIC, which is 20mA, I believe.

Was planning to do something like this, as I did with the Gristleizer:

http://img101.imageshack.us/img101/9657/ledflash.jpg

Alright, I think I'm understanding. I don't the chip can do what I was thinking of - the ability to set the rate knob to something generic, and then be able to switch tempo back and forth between the tap tempo and the knob by 'holding' the switch or something like that.

I think Taylor, the pcb you're designing is great, and I don't know who else is going to build it, but I sure am. Make me a PCB when you finish it and I'll pony up!

I'm jumping in a bit late, but here goes anyway;

jkokura, you're right, the chip *won't* do what you want. There's only one tempo, so you can't switch between the speed set by the knob or the speed set by tapping.
Just to be clear (although someone had this right already) if you twist the knob, you get the tempo set by the knob. If you tap the button, you get the tempo set by the taps. It stays that way until you either tap again or twist again (like you did last summer?).
The code as currently written uses two taps to set the tempo. If you give it two new taps, it resets the tempo based on those - it doesn't average them. It also resets the waveform to the start on the first tap. If you give it only one tap, it'll wait about three and a half seconds for another, before ignoring the 'unpaired' tap. These two features together mean that it is possible to bring the LFO back into line with what you're playing by giving it a single tap.
Oh, and sorry to Mike, but the full Waveform Distortion CV had to go. The sums that are required for it use up a lot of time, time that I needed for other features. I left a straightforward Pulse Width CV because that is simple to do, but it only works on the Pulse wave, whereas the VCLFO code allows the waveform distortion to affect *all* the waveforms.

Hope that clears a few things up!

Thanks,
Tom

Great work Tom! I have a question for you.

Assume you tapped four beats fairly quickly (ie under 3.5 seconds) Is the tempo then taken from the first two (beats 1 and 2) or the last two (3 and 4)? Also, how much additional coding is required to allow averaging? For instance, tempo is defined by the average of the most recent 4 taps, or however many occurred in the last 4 seconds or something to that degree?

You digitally inclined folks never cease to amaze me.

Quote from: ianmgull on December 12, 2009, 04:25:05 PM
Great work Tom! I have a question for you.

Assume you tapped four beats fairly quickly (ie under 3.5 seconds) Is the tempo then taken from the first two (beats 1 and 2) or the last two (3 and 4)? Also, how much additional coding is required to allow averaging? For instance, tempo is defined by the average of the most recent 4 taps, or however many occurred in the last 4 seconds or something to that degree?

You digitally inclined folks never cease to amaze me.

Ian,
The last two taps would override the tempo set by the first two. Averaging is possible, but involves division, which is a very costly operation on such cheap chips since they don't have "divide" instructions or even "multiply". This means you have to program division yourself, which is slow.
One way around this is to use binary shifting instead, which gives you division by powers of two (/2, /4, /8 etc) but unfortunately this isn't ideal for tap tempo, since four taps gives *three* times, and division by three is evil - ask any assembly programmer!
So, yes it's do-able, but I didn't do it because it's better avoided if possible. I did wonder about doing a four-tap average, but only using the times between taps one and two, and between taps three and four. Avoiding the time between taps two and three only gives me two times, and as I said, division by two is easy. Might this be a good compromise?

Is averaging of more taps something that everyone would really like to see?

T.

 I think it would be fine either way, we just need to understand what to do and what not to do.

Knowing that it only takes my first two, or second two taps as average, I'd be very careful to make sure I tapped well. Averaging out 3, 4, 5, etc. taps is a cool thing, but if it's too hard to program in on these than don't bother.

Jacob

Quote from: ElectricDruid on December 12, 2009, 02:36:31 PM
... it is possible to bring the LFO back into line with what you're playing by giving it a single tap.

I think that's a brilliant feature!  8)

Tom, now that I think about it you've got it all figured out! My frame of reference comes from a tap delay which is slightly different due to the fact that there isn't an LFO to stay in sync with.  With the tremolo you more than likely would want to stay in sync with the LFO so it makes perfect sense that it resets based on the most recent taps.

One other thing I wanted to mention is that the taps need to set not only the speed but also the phase of the waveform. The wave should be reset to its highest peak when the second tap happens.

I remember a few years ago a certain boutique pedal company came out with a tap tempo trem, but the control was such that the wave would start at the center of its period (i.e., the point of zero crossing) when the tap button was pushed. For tapping out a speed before you begin playing, this is fine, but if the song has already started, this makes your notes only sound on the off beats. Fine for ska, but it's generally not the behavior people are looking for.

I'm guessing this is already the case in your chip, Tom, since it's kind of the obvious way to work, but I did want to mention it since it slipped the mind of that other guy, and his was a commercial unit.

Now, for sine, triangle, lumps, etc., I think the "beat" is perceived to be right at the highest peak of the wave, which for all these waves is halfway between zero-crossings. However, it gets hairier with a square wave, as there's no ramping up, so the "beat" is more likely to be heard at the point of zero crossing. I don't know if the limitations of the chip allow for different reset points for different waves - I'm guessing that's a little too complex here, so I don't really know how that should be handled.

Hi Tom,

I am wondering if any future revisions to this chip will keep the same pinouts? I.E. anything with extra features will be placed on RC2, any throwback to the earlier wave distort feature will be in place of the current pulse width CV...? I just want to make sure that I can design while keeping future possibilities in mind.

I've been messing with it on the breadboard, and it's a wonderful chip.

Taylor:

In regard to your point about the square waves "start". I suspect that this might be dependent on the symmetry of the square wave. Does anybody know if both the positive and negative portions of the cycle are equal? Many tremolos (even on the square wave setting) seem to be weighted slightly in one direction or the other. This could alter whether or not it feels like your first note is on the downbeat.

Since this is a digitally derived LFO, I'm guessing the square wave is a true 50% duty cycle square.

Quote from: flo on December 13, 2009, 03:02:08 PM

Quote from: ElectricDruid on December 12, 2009, 02:36:31 PM
... it is possible to bring the LFO back into line with what you're playing by giving it a single tap.

I think that's a brilliant feature!  8)

Absolutely, that would be really exciting, as far as syncing the phase to music.  Maybe for the deluxe program, instead of the first tap reseting the waveform immediately  it sorta speeds it up to be in phase on the middle of the next beat so it doesn't glitch the sound with a sudden transition on the ramp up or sinewave?

Quote from: ElectricDruid on December 13, 2009, 06:42:22 AM

Is averaging of more taps something that everyone would really like to see?

T.

It would help scientifically for better timing (when editing audio into loops I've had good luck starting with several measures and then dividing that down, as far as getting a truer timing of a single measure, that can stay in time with the original tempo longer, before it starts to drift out of phase).

But asking a musician to be able to tap their foot on time isn't exactly unreasonable :icon_smile:, and it sounds like a can of worms to get into averaging.  Measuring the last two taps is wonderfully simple and straightforward.

All `yall had to do this just as I was finishing up my MV-53 based tap trem, didn't you?


I'm about to plug it in and see if it works, but it appears to be good.  Everything but sound is testing right, so I guess its time to give it a listen, right?

I normally only ever lurk here, and i haven't check in over a week because I've been working on this thing.  And now you tell me there is going to be a pre-made board?  Thanks a lot! ;) ;) ;)



Gabriel

Quote from: G. Hoffman on December 14, 2009, 04:27:51 AM
All `yall had to do this just as I was finishing up my MV-53 based tap trem, didn't you?

I'm about to plug it in and see if it works, but it appears to be good.  Everything but sound is testing right, so I guess its time to give it a listen, right?

I normally only ever lurk here, and i haven't check in over a week because I've been working on this thing.  And now you tell me there is going to be a pre-made board?  Thanks a lot! ;) ;) ;)

Gabriel

I may be more than a little biased, but I think you will find MV-53 to be a superior choice for the following reasons:

* The waveforms are analog (from an on-board Digital Analog Converter) and as clean as you can imagine, including the sine waves - no PWM filtering required, and the sample rate is many times higher (1.23 MHz)

* MV-53 has a duty cycle control to skew the waveforms "on the fly" using 11 different musical ratios that can "swing": 1/8, 1/6, 1/4, 1/3, 3/8, 1/2, 5/8, 2/3, 3/4, 5/6, 7/8

* MV-53 lets you switch between potentiometer and tap controlled tempos "on the fly"

* MV-53's tap control has tested accuracy of better than 1/1000th of a second

* MV-53 outputs two simultaneous waveforms (one is inverted)

* MV-53 allows the user to program sequences of waveforms and playback rates to add much more interesting rhythmic elements to your effects

* MV-53 stores 9 different user-defined programs, and also has a "free running" mode

* MV-53 allows a real-time LED interface indicating current waveform and playback speed

* Its very easy to defeat any MV-53 features you don't want to use

More info is available here, as well as a video demo:
http://www.moltenvoltage.com/mv-53.html

Quote from: MoltenVoltage on December 14, 2009, 04:34:45 PM

Quote from: G. Hoffman on December 14, 2009, 04:27:51 AM
All `yall had to do this just as I was finishing up my MV-53 based tap trem, didn't you?

I'm about to plug it in and see if it works, but it appears to be good.  Everything but sound is testing right, so I guess its time to give it a listen, right?

I normally only ever lurk here, and i haven't check in over a week because I've been working on this thing.  And now you tell me there is going to be a pre-made board?  Thanks a lot! ;) ;) ;)

Gabriel

I may be more than a little biased, but I think you will find MV-53 to be a superior choice for the following reasons:

* The waveforms are analog (from an on-board Digital Analog Converter) and as clean as you can imagine, including the sine waves - no PWM filtering required, and the sample rate is many times higher (1.23 MHz)

* MV-53 has a duty cycle control to skew the waveforms "on the fly" using 11 different musical ratios that can "swing": 1/8, 1/6, 1/4, 1/3, 3/8, 1/2, 5/8, 2/3, 3/4, 5/6, 7/8

* MV-53 lets you switch between potentiometer and tap controlled tempos "on the fly"

* MV-53's tap control has tested accuracy of better than 1/1000th of a second

* MV-53 outputs two simultaneous waveforms (one is inverted)

* MV-53 allows the user to program sequences of waveforms and playback rates to add much more interesting rhythmic elements to your effects

* MV-53 stores 9 different user-defined programs, and also has a "free running" mode

* MV-53 allows a real-time LED interface indicating current waveform and playback speed

* Its very easy to defeat any MV-53 features you don't want to use

More info is available here, as well as a video demo:
http://www.moltenvoltage.com/mv-53.html

Oh, I'm not dissatisfied with it.  However, if I could have used someone else's circuitboard, instead of having to design my own, it would have made life much easier.  I'm kind of lazy that way, sometimes!

By the way, any hints on getting rid of the clicking I'm getting in Square and Sawtooth modes?  I'm assuming it is to do with my circuit board design or some such, but any hints would be appreciated.  Also, was I just wasting space on my PCB by putting current limiter resistors on the program inputs?  Other than the clicking it worked perfectly on fire up (shocked the heck out of me!  That never happens to me, and I was particularly shocked as I didn't breadboard the circuit), but the current limiting resistors are taking up a fair bit of real estate that I would like to use for other things.

{edit}  OH! And I think you might want to change the depth control in your tremolo circuit to a audio taper pot - the sweep is kind of sudden.{/edit}


Gabriel

We didn't notice any clicking on our prototype when using only the Tremolo, but we did have that problem on the VCF circuit when using square or sawtooth waves.  Take a look at the pop filter we used on the VCF schematic:
http://www.moltenvoltage.com/downloads/MV-53_-_VCF_Schematic_-_Molten_Voltage_v1.bmp

Also take a look at how we did it with the MV-52 circuit - the 100uF cap to ground right before the optocoupler did the trick.
http://www.moltenvoltage.com/downloads/Application_Note_1_for_MV-52_-_v1_1_-_Molten_Voltage.pdf

Try placing a cap to ground in front of the optocoupler (after the 4.7K resistor).  100uF is a good place to start.  If you still have issues, try a larger value.  If it is dead silent, try going down in value, as the higher the value cap, the more it rounds off the corners of the square wave, and the less "choppy" it will be.

You don't need any resistors that aren't shown in the schematic:
http://www.moltenvoltage.com/downloads/MV-53_Tremolo_Schematic_v1.jpg

When you say "current limiting resistors on the program inputs", I assume you mean the Program Pins (4, 5, 6, 7, 9, 10, 11, 25, & 26).  These have internal weak pullups so no need for a pullup resistor.  They get pulled to ground when engaged, so no need to limit the current either.  If you don't want to use any program features, just leave them all unconnected - then the chip will remain in "free running" mode.

Thanks for the tip on the depth control!

A real fun way to use the LFO (especially if you like to experiment) is to put it in a separate box like in our video, then have a jack that lets you connect to your LFO-based effects.

Thanks to Taylor for pointing out that the 'beat' in a sine wave is at the top of the waveform. It *is* obvious, but I *had* forgotten to think about that. I'll have a play with the waveform tables to take that into account.
It'd be nice to be able to smooth the transition when you tap a single tap to reset the phase of the waveform and keep it in sync, but to be honest, I don't think it's do-able. At least, not on this chip.

The square wave width is variable using the Pulse Width CV, so it's only square if you feed 2.5V into that input.

As to MoltenVoltage's comments, mostly I agree entirely - they've got a bigger chip and bigger feature set. I've done other LFOs on the 16-bit dsPIC series chips, and you can get better quality output. My tap tempo LFO is small, simple, and cheap (The chips cost £1 / $1.50). Code is available for tweaking, but it's only an 8-bit chip. Ultimately, they're rather different beasts. You decide whether you need the extra features and quality of the Molten Voltage chip and whether that makes it worth it for your application.

In one detail, my little PIC does keep up with their chip. The timing accuracy is much better than 1/1000th of a second - in fact 1/19500th of a second.

Thanks to everyone for all the support with this project,
Tom

Quote from: ElectricDruid on December 17, 2009, 11:09:48 AM
Thanks to Taylor for pointing out that the 'beat' in a sine wave is at the top of the waveform. It *is* obvious, but I *had* forgotten to think about that. I'll have a play with the waveform tables to take that into account.
It'd be nice to be able to smooth the transition when you tap a single tap to reset the phase of the waveform and keep it in sync, but to be honest, I don't think it's do-able. At least, not on this chip.

The square wave width is variable using the Pulse Width CV, so it's only square if you feed 2.5V into that input.

As to MoltenVoltage's comments, mostly I agree entirely - they've got a bigger chip and bigger feature set. I've done other LFOs on the 16-bit dsPIC series chips, and you can get better quality output. My tap tempo LFO is small, simple, and cheap (The chips cost £1 / $1.50). Code is available for tweaking, but it's only an 8-bit chip. Ultimately, they're rather different beasts. You decide whether you need the extra features and quality of the Molten Voltage chip and whether that makes it worth it for your application.

In one detail, my little PIC does keep up with their chip. The timing accuracy is much better than 1/1000th of a second - in fact 1/19500th of a second.

Thanks to everyone for all the support with this project,
Tom

I couldn't agree more that there are trade-offs between the two chips, but I must take issue with your accuracy claims.

Please correct me if I am wrong, but I cannot imagine you have actually rigorously tested and proven that accuracy like we have.  Mathematically, ours should be much more accurate (nearly 1/40,000,000th of a second), but can never be because of physical limitations.  Further, changing the placement of the 0.1uF bypass cap by 2 millimeters can cut tap accuracy in half (down to 1/500th of a second).  I know you are giving away your code, which is very generous of you and great for the DIY community here, but I really think you need to have your facts straight before making specific performance claims.

Again, if you have tested and I am wrong, I apologize.

Would it really make a difference,

It's not like you can tap your foot to even a 1/2 second accuracy, much less 1/1,000 or 1/40,000,000  :icon_lol:

Although I suppose any claim is worth arguing over in the marketing world.  :icon_biggrin:

I'm not making any enormous accuracy claims. All I was referring to is that the timer that times the time between taps is clocked at 19500Hz, so it's accurate to better than 1mS - it's a crystal clock, after all. And no, I haven't tested it - what need? I agree with JKowalski; the big timing error is the human doing the tapping anyway!

Tom

Even though 1ms accuracy isn't that big of a deal playing live if you have a "flexible" drummer, accuracy is an issue if you are playing along with other tracks while overdubbing.

Assume a typical song of 120 bpm (2 beats per second : 500 ms between beats)
If this is a 3 minute song, it is 180 seconds (180,000 ms) long.

Now assume you want the effect tempo at 1/4 notes, you are at 125ms between quarter notes.

Even your effect gets out of time only 1ms per second, by the end of the song (180 seconds), you are well over a quarter note out of time (180ms).

Instead of being on the downbeat, you are well past the snare beat.

Even if you wouldn't usually use an effect for a whole song, you can calculate the degree to which you will be out of sync based on the length of time the effect will be on.  The obviousness of this effect depends on the type of effect you are using, but a VCF type effect or chopper tremolo will be easy to hear if its out of time, while a soft flanger might not.

While you might not be able to tap within a 1/2 second of the beat, I've met plenty of pros that can nail it.  I guess the degree of accuracy you require depends on who the end user is going to be.

Quote from: MoltenVoltage on December 17, 2009, 11:32:20 PM
Even though 1ms accuracy isn't that big of a deal playing live if you have a "flexible" drummer, accuracy is an issue if you are playing along with other tracks while overdubbing.

Assume a typical song of 120 bpm (2 beats per second : 500 ms between beats)
If this is a 3 minute song, it is 180 seconds (180,000 ms) long.

Now assume you want the effect tempo at 1/4 notes, you are at 125ms between quarter notes.

Even your effect gets out of time only 1ms per second, by the end of the song (180 seconds), you are well over a quarter note out of time (180ms).

Instead of being on the downbeat, you are well past the snare beat.

Even if you wouldn't usually use an effect for a whole song, you can calculate the degree to which you will be out of sync based on the length of time the effect will be on.  The obviousness of this effect depends on the type of effect you are using, but a VCF type effect or chopper tremolo will be easy to hear if its out of time, while a soft flanger might not.

While you might not be able to tap within a 1/2 second of the beat, I've met plenty of pros that can nail it.  I guess the degree of accuracy you require depends on who the end user is going to be.

You're assumption is that first, the tempo will not be reset/recalibrated at all during the song, this negates the necessity of a tap tremolo to begin with. Second, that someone would actually be able to tap with 1ms of the tempo of a "flexible" drummer (that's 1/1000 of a second, nobody got that much rhythm). I have to agree that these differences seem like somebody trying to push their product a bit too hard.

...and if you're accurate to 1/1000th of a second, all the time,  *everytime*, you may as well be a machine.

:icon_wink:

This is a bunny trail and defeats the purpose of this thread I think. While I agree MV, it's important to test and the accuracy and quality of your chip is excellent. I'm sure many of us would like to see it used. However, we're trying to design a Tap tempo tremolo circuit here. If you'd like to offer your input based on the last 5 pages, perhaps come up with a schem, including your chip, we would appreciate that. If I understand correctly, you've already done that to a certain extent, however I looked at your video with the crazy external tap tempo box and I was overwhelmed.

We're trying to design a simple trem, with some important features, and if you and anyone else would like to contribute wonderful, but arguing about the veracity of calculations in your chip versus someone elses... Go somewhere else and do that. Nobody really needs to watch that argument take place, and it doesn't help us get a PCB together with a project file that anyone can etch, get the parts for and build to show off.

Sincerly, and with all due respect.

Jacob

By the way, I think the MV52 has more potential for the application we're thinking of also.

Jacob

Ok, I got side tracked by some other things, but the PCB is under way. Hopefully will have proto boards in a couple of weeks, followed by boards for you guys in about a month.

This'll be fun, I haven't had a really nice trem since I sold all my pedals a few years ago, in a baffling haze, thinking that computer processing had hardware effects obsolete. Now I know better.

The PCB is complete. I'm trying an interesting grounding scheme on this one, using separate ground planes for the audio and digital section, and then connecting them at a single point. Should hopefully keep things sounding nice and clean with no ticking.

For my personal taste, a 1590BB box is about right for something with 2 stomps and 4 or 5 knobs. In fact, I just like gigantic metal boxes (http://www.diystompboxes.com/smfforum/index.php?topic=74465.0). But just because I know how much you guys love fitting everything into tiny boxes, I designed the board to fit into a 1590B! It should work either with Electric Druid's TapLFO chip (http://www.diystompboxes.com/smfforum/index.php?topic=76436.0) or JKowalski's modified code, and I included an option to add the "Wave Distort" knob (duty cycle that works on all waveforms) if using the modified code.

I decided to go with this chip rather than the others for a few reasons. The main thing is that it is "open". The code is open to be changed by the community, which is in line with the spirit of this forum. Also it's cheap. I will be talking to Electric Druid and JKowalski to orchestrate the availability of these chips for people who aren't able to program their own PICs. I will also hook you guys up with part numbers for the crystal oscillator, etc. so this project will be buildable for all.

I used this crystal from Mouser (although I bought mine from Newark):

http://www.mouser.com/Search/Refine.aspx?Keyword=73-XT49S2000-20

If I recall correctly, I chose them because they were shorter than most of the other crystals I saw. You can see them in this image (http://img189.imageshack.us/i/boardfilledtop.jpg/) and this image (http://img141.imageshack.us/i/boardfilledperspective.jpg/).

:)

MIke

I'm in for two PCB's if you're getting them made, or if you're going to be making a Trace you can etch than make an extra two for me Taylor!

Jacob

These will be pro double sided boards with silk screen, plated pads, solder mask, the whole deal. So much nicer than building on home etched boards! I have a hard time going back to homemade boards now that I'm spoiled on pro boards...

Quote from: .Mike on January 29, 2010, 01:07:01 AM
I used this crystal from Mouser (although I bought mine from Newark):

http://www.mouser.com/Search/Refine.aspx?Keyword=73-XT49S2000-20

If I recall correctly, I chose them because they were shorter than most of the other crystals I saw. You can see them in this image (http://img189.imageshack.us/i/boardfilledtop.jpg/) and this image (http://img141.imageshack.us/i/boardfilledperspective.jpg/).

:)

MIke

Used the same, think it was the cheapest and smallest on mouser.


Taylor, what are you doing with pin 8 of the PIC chip? It's typically unused but suits itself nicely to modifications. It might be useful to modify the board to allow future options on this pin (ex. that waveform select switch I added on one of my mods)

For example putting an optional pullup to V+ on that pin and a pad to connect externally would give the option of adding a momentary switch to it.

Just to give you an idea it is a very versatile pin, it can be used for a CV input, or digital I/O.

Ok, I'll do that.

Edit: done.  :)

Just a note to say in public that I'm sorting out chips for Taylor, so he'll be able to supply programmed chips with the PCBs for anyone who wants one.

If you're into PICs (or would like to be), you're still free to download the code from either me or JKowalski's site, and then you can play with it too. But if you do anything really cool, be sure to tell us all about it!

My site, with my original code:
   http://www.electricdruid.com/
The Kowalski variations!:
   http://strangedesigncs.heliohost.org/

T.

Yep, I'll sell the chips along with the PCBs so you can avoid double shipping charges.

JKowalski mentioned to me that there is an unused pin on the chip which could be put to use. Anybody have any thoughts on extra features we could add to this? His idea was a stomp switch to swap between tapped speed and the speed pot. I was thinking maybe a half time stomp would be good, or a stomp to cycle through time divisions.

Quote from: Taylor on February 01, 2010, 11:10:52 PMJKowalski mentioned to me that there is an unused pin on the chip which could be put to use. Anybody have any thoughts on extra features we could add to this? His idea was a stomp switch to swap between tapped speed and the speed pot. I was thinking maybe a half time stomp would be good, or a stomp to cycle through time divisions.

Well, I'm not exactly a prospective customer, as my favorite part of this whole electronics thing so far is designing circuit boards, and I've already programed a few of these chips for bread boarding, but it seems to me that, as JKowalski has gone to the effort of creating several options, you might want to just have it go to a wire connection so people can chose different options.  If I remember right, at least one of JK's variations use a pot in that position, others a switch, and even if he hasn't yet, a pot is a possibility for future variations.  A small sub board, or possibly even just some point to point parts, would work fine for the functions of one pin.  Particularly as you have (I believe) already said the board was getting a bit crowded.

But as I said, mine is hardly the pertinent opinion on the matter.


Gabriel

Sign me up for a couple of boards and chips !!  I will excited to see how this all turns out.

I would really love it if the board would fit in a 125B box, I don't mind tightly spaced footswitches.

Taylor can you provide a parts list as soon as the design is finalized so that we can order them ahead of time?  Thanks.

Quote from: G. Hoffman on February 02, 2010, 06:29:53 AM

Quote from: Taylor on February 01, 2010, 11:10:52 PMJKowalski mentioned to me that there is an unused pin on the chip which could be put to use. Anybody have any thoughts on extra features we could add to this? His idea was a stomp switch to swap between tapped speed and the speed pot. I was thinking maybe a half time stomp would be good, or a stomp to cycle through time divisions.

Well, I'm not exactly a prospective customer, as my favorite part of this whole electronics thing so far is designing circuit boards, and I've already programed a few of these chips for bread boarding, but it seems to me that, as JKowalski has gone to the effort of creating several options, you might want to just have it go to a wire connection so people can chose different options.  If I remember right, at least one of JK's variations use a pot in that position, others a switch, and even if he hasn't yet, a pot is a possibility for future variations.  A small sub board, or possibly even just some point to point parts, would work fine for the functions of one pin.  Particularly as you have (I believe) already said the board was getting a bit crowded.

But as I said, mine is hardly the pertinent opinion on the matter.


Gabriel

None of them use a CV on pin 8. I can't really think of any mod that might need a CV... The chip's got so many options already. A digital input seems the most useful, to allow more foot control over parts of the chip's operation.

I suggested that something might be put on the pin because I think most of the people ordering these boards will be doing so because they do not have the ability to program themselves, so... Adding another feature would let the people who can't reprogram to have something else available, and the people who want to reprogram can still do it with no issues...

I asked taylor earlier to put an optional pullup and pad of pin 8 so that you can use it as a digital input simply by connecting a mom. switch to ground the pin. Using it as a CV input, you could just not add the pullup and connect a pot to the pad instead. Using it as an output (say an LED) would be fairly easy.

If we can't think of anything terribly useful then I guess we can just forget it. But I did like the multiplier cycle control, that might be useful in a live setting.

Yep, the board has a pad to access pin 8 with a pullup to 5v. So adding a momentary switch is already supported in the hardware, whatever the code does with it.

I'm thinking the most useful thing would be to cycle through multiplier settings, but the implementation would be tricky. Since this would be a performance control, it's important that it would maintain phase when stepping through multiply settings. So say I'm playing in a straight 4/4 time, using the 4 multiply. Then I step to 3 multiply to get a 3-on-4 feel. Then I click through to 2 multiply. At this point, at least if we assume that I stomped on the multiple select switch right on beats, the 2 multiply should be falling on the same beats as the 4 multiply was, except half as often. It shouldn't go out of sync when changing multiply settings.

So maybe the switch should simultaneously reset the wave phase and change multiplier? This would seemingly keep everything nicely lined up.

There's another concern that I think would be harder to deal with. If using a sine wave for example, it would be ideal if there wasn't a discontinuity heard when selecting multipliers and resetting phase. Ideally, it should smoothly blend from wherever the wave happens to be at the moment of the press to the beginning of the next wave. This might be as easy as a lowpass filter that's placed on the output of the wave only during the moment of phase reset. My digital knowledge is limited to DSP on the FV-1 (and just limited in general) so I don't know whether this would work for the hardware involved here.

Also, Chris, did either you or Tom ever address the thing I brought up a few pages back about where the start of each waveform table should be? Like, the sine and similar waves need to reset at their peak, but the square wave should reset at the positive-going edge?

Quote from: oliphaunt on February 02, 2010, 11:05:42 AM
Sign me up for a couple of boards and chips !!  I will excited to see how this all turns out.

I would really love it if the board would fit in a 125B box, I don't mind tightly spaced footswitches.

Taylor can you provide a parts list as soon as the design is finalized so that we can order them ahead of time?  Thanks.

I'm pretty positive this will fit in a 125b, unless you want the third footswitch we're discussing above. So we'll give ZVex a run for his money. :D

I'll get a real parts list together soon. Here's the automatic one my CAD program spit out:

item qty       part type       values

1   14   box metal film cap   22P   100NF   100NF   100NF   1UF   330P   1UF   100NF   100N   100NF   

               330NF   100NF   22P   XTAL   

2   1   DIP14      TAPLFO   

3   1   DIP8      TL072   

4   1   DO34      1N4001   

5   2   ELECTRO      10UF   100UF   

6   1   OPTO      OPTO   (haven't figured out the right opto yet, will need to experiment when I get the proto boards)

7       4 or 5       potentiometer           B10k all

10   19   resistor      1M   10K   220K   220K   1M   1K   150R   1K   10K   1K   

               100K   150R   10K   10R   100K   10K   3K6   EXP   1K   

11   2   TO-92                  78L05   2N3904   

12   1   TRIM_MINI      10K   

Quote from: JKowalski on February 02, 2010, 12:35:56 PM

Quote from: G. Hoffman on February 02, 2010, 06:29:53 AM

Quote from: Taylor on February 01, 2010, 11:10:52 PMJKowalski mentioned to me that there is an unused pin on the chip which could be put to use. Anybody have any thoughts on extra features we could add to this? His idea was a stomp switch to swap between tapped speed and the speed pot. I was thinking maybe a half time stomp would be good, or a stomp to cycle through time divisions.

Well, I'm not exactly a prospective customer, as my favorite part of this whole electronics thing so far is designing circuit boards, and I've already programed a few of these chips for bread boarding, but it seems to me that, as JKowalski has gone to the effort of creating several options, you might want to just have it go to a wire connection so people can chose different options.  If I remember right, at least one of JK's variations use a pot in that position, others a switch, and even if he hasn't yet, a pot is a possibility for future variations.  A small sub board, or possibly even just some point to point parts, would work fine for the functions of one pin.  Particularly as you have (I believe) already said the board was getting a bit crowded.

But as I said, mine is hardly the pertinent opinion on the matter.


Gabriel

None of them use a CV on pin 8. I can't really think of any mod that might need a CV... The chip's got so many options already. A digital input seems the most useful, to allow more foot control over parts of the chip's operation.

I suggested that something might be put on the pin because I think most of the people ordering these boards will be doing so because they do not have the ability to program themselves, so... Adding another feature would let the people who can't reprogram to have something else available, and the people who want to reprogram can still do it with no issues...

I asked taylor earlier to put an optional pullup and pad of pin 8 so that you can use it as a digital input simply by connecting a mom. switch to ground the pin. Using it as a CV input, you could just not add the pullup and connect a pot to the pad instead. Using it as an output (say an LED) would be fairly easy.

If we can't think of anything terribly useful then I guess we can just forget it. But I did like the multiplier cycle control, that might be useful in a live setting.

Makes sense.  Though, really, the pads you need for either a pot or a switch are the same - one for +V, the pin itself, and ground.  It would be pretty easy to put in pads for either, and wouldn't take up much extra space.


Gabriel

I don't think you need to ground the pin when not connected to V+, you can just leave it floating, right?

Quote from: Taylor on February 02, 2010, 03:52:08 PM
I don't think you need to ground the pin when not connected to V+, you can just leave it floating, right?

:o

Quote from: Taylor on November 14, 2009, 10:11:29 PM
I still consider myself a noob with electronics

:icon_wink:

I reserve the right to be very wrong. However, I thought that that's what JKowalski told me, but there's a good chance I misunderstood.

Quote from: Taylor on February 02, 2010, 08:50:05 PM

Quote from: Taylor on November 14, 2009, 10:11:29 PM
I still consider myself a noob with electronics

:icon_wink:

I reserve the right to be very wrong. However, I thought that that's what JKowalski told me, but there's a good chance I misunderstood.

Even if it's possible, it is always better to give a pin on any IC a definitive reference.  Now, you could have it tied to ground or to V+ internally by programing it appropriately (or so I assume, since that is what Molten Voltage has done with the MV-53).  But even then, you may as well tie it to the appropriate rail. 

Or at least, that is the way I understand it.  I too could be very wrong.


Gabriel

make unused pins an output and send low and don't connect to anything

Perhaps you could use it as an inverted (phase) output, to make stereo delay easier. Or even better, you could perhaps have it function as a multiplied/divided output. That way you could have a trem doing 1/4's on the left, and 1/16's on the right, or whatever. 

The unused pin can not be setup as PWM so it can't provide an LFO output. So best use would be for some sort of control input.

Quote from: Taylor on February 02, 2010, 03:17:26 PM
Yep, the board has a pad to access pin 8 with a pullup to 5v. So adding a momentary switch is already supported in the hardware, whatever the code does with it.

I'm thinking the most useful thing would be to cycle through multiplier settings, but the implementation would be tricky. Since this would be a performance control, it's important that it would maintain phase when stepping through multiply settings. So say I'm playing in a straight 4/4 time, using the 4 multiply. Then I step to 3 multiply to get a 3-on-4 feel. Then I click through to 2 multiply. At this point, at least if we assume that I stomped on the multiple select switch right on beats, the 2 multiply should be falling on the same beats as the 4 multiply was, except half as often. It shouldn't go out of sync when changing multiply settings.

So maybe the switch should simultaneously reset the wave phase and change multiplier? This would seemingly keep everything nicely lined up.

There's another concern that I think would be harder to deal with. If using a sine wave for example, it would be ideal if there wasn't a discontinuity heard when selecting multipliers and resetting phase. Ideally, it should smoothly blend from wherever the wave happens to be at the moment of the press to the beginning of the next wave. This might be as easy as a lowpass filter that's placed on the output of the wave only during the moment of phase reset. My digital knowledge is limited to DSP on the FV-1 (and just limited in general) so I don't know whether this would work for the hardware involved here.

Also, Chris, did either you or Tom ever address the thing I brought up a few pages back about where the start of each waveform table should be? Like, the sine and similar waves need to reset at their peak, but the square wave should reset at the positive-going edge?

Hi, I'll look into the things that you mentioned this weekend. I've had a rough week and haven't had much time to work on anything.

I don't think it will be possible (well, easy) to come up with a solution to the discontinuity during phase resets. Although I will try to figure something out for the multiplier change... so that it only activates the change when the phase ends back up at zero.

I think the wave phase start issue was never resolved, again I will look into it and change it if necessary.


So what's the decision as far as the unused pin? It's up to you in the end, Taylor.

I have another suggestion to throw out there, and that is whether or not the random waveform should be kept.

Molten Voltage, that would be a good plan but you invite the risk (though small) of damaging the not-so-easily replaceable chip by hitting the pins with a voltage.... *shrug*

And Gabriel, the PICs do have weak internal pullups but they are only on PORTA for the PIC16F684, if I remember correctly. Not the unused pin.

I think Tom is working on the multiplier step switch. He also says that the wave thing is fixed in his code, I think he had to take your code with the wave distort and the phase thing and put them together. So you guys could discuss it, but I think he's on it.

I am indeed!

I've been tinkering about with it this afternoon, and I've got Version 2 code up on my site:

http://www.electricdruid.com/index.php?page=projects.taplfo

This includes the Wave Distort CV that JKowalski put in, and my adjustments to wave start positions. It also uses pin 8 as a digital input to step through the multiplier settings.

Taylor, I can't work out if it'll do what you suggested with the taps - running at 4/4, you tap and go to triplets, count 3, tap and go to 8/4? Does that work out? Anyway, the chip does it, musical or not.

I think unless anyone has any unmissably great ideas or finds any bugs, I have to regard this as the final version and start getting some chips programmed. The alternative is that we spend forever tweaking and never get any units built!

Thanks,
Tom

Quote from: ElectricDruid on February 06, 2010, 04:53:14 PM
Taylor, I can't work out if it'll do what you suggested with the taps - running at 4/4, you tap and go to triplets, count 3, tap and go to 8/4? Does that work out? Anyway, the chip does it, musical or not.

It's kind of hard to describe what I was talking about. If the multiplier tap switch could also reset the phase whenever you go into a new multiple setting, that would be ideal. Is that how it works now?

QuoteI think unless anyone has any unmissably great ideas or finds any bugs, I have to regard this as the final version and start getting some chips programmed. The alternative is that we spend forever tweaking and never get any units built!

Thanks,
Tom

I definitely agree.

I think what you guys have done is not only great compared to DIY projects, but actually better than the commercial tap tempo trems out there in terms of features. The only small fret I have is if the use of the LDR is going to smear some of the subtleties of the different waveforms out. But I think this is one of the coolest DIY projects so far.

Quote from: ElectricDruid on February 06, 2010, 04:53:14 PM
I am indeed!

I've been tinkering about with it this afternoon, and I've got Version 2 code up on my site:

http://www.electricdruid.com/index.php?page=projects.taplfo

This includes the Wave Distort CV that JKowalski put in, and my adjustments to wave start positions. It also uses pin 8 as a digital input to step through the multiplier settings.

Taylor, I can't work out if it'll do what you suggested with the taps - running at 4/4, you tap and go to triplets, count 3, tap and go to 8/4? Does that work out? Anyway, the chip does it, musical or not.

I think unless anyone has any unmissably great ideas or finds any bugs, I have to regard this as the final version and start getting some chips programmed. The alternative is that we spend forever tweaking and never get any units built!

Thanks,
Tom

Well, let's see. We want the LFO to be based around the 0.5 multiplier, and not deviate from that basic interval no matter what multiplier setting is pressed.

Here is how it should go. Synchronized to the base interval (1) and the multiplication just divides that interval.

|               | 1
|       |       | 2
|    |     |    | 3
|   |   |   |   | 4
|  |  |   |  |  | 5
| |  |  |  |  | | 6
| | | | | | | | | 8

But our problem arises because the multiplier increases the phase increment at the point at which it was told to change, which can speed up the wave in the middle of the phase counter and that will throw everything totally out of whack - each multiplier change scoots the phase accumulator out of the base interval.

The only thing I can think of is to set up a counter that counts the cycles of the phase accumulator, compares is to the multiplier setting, and sets a flag when they equal. When the flag is set, the pending change in the multiplier settings will finally be uploaded into the frequency increments.

To keep the changes pending, the multiplier calculation can be done in the main loop and sent to a FREQ_INC_TEMP instead of the FREQ_INC. Then that TEMP is loaded into the real one when necessary. That way you can accumulate changes in the multiplier as well while it is waiting for the cycle to end and update to come (i.e. if you hit it more then once while the code is waiting for the update it will register every tap you input)

Basically what this would do is allow the chip to wait until the interval that is common to all of the multipliers (the lowest multiplier) is finished before it goes to the new multiplier, so that it doesn't throw it all out of whack.

There is the fact that you have to wait for the lowest interval to finish so at slow settings this may be a while.... But this is the only way I can imagine you would be able to do it. Resetting the phase directly on change would throw the LFO out of sync if you don't count the beats correctly, like Tom said... And by the way, counting the beats would end up doing the same thing as the idea I just laid out anyways  :icon_rolleyes:  I suppose it's just the same idea in an automatic way.

*shrug*

Quote from: Taylor on February 06, 2010, 05:20:15 PM

Quote from: ElectricDruid on February 06, 2010, 04:53:14 PM
Taylor, I can't work out if it'll do what you suggested with the taps - running at 4/4, you tap and go to triplets, count 3, tap and go to 8/4? Does that work out? Anyway, the chip does it, musical or not.

It's kind of hard to describe what I was talking about. If the multiplier tap switch could also reset the phase whenever you go into a new multiple setting, that would be ideal. Is that how it works now?

QuoteI think unless anyone has any unmissably great ideas or finds any bugs, I have to regard this as the final version and start getting some chips programmed. The alternative is that we spend forever tweaking and never get any units built!

Thanks,
Tom

I definitely agree.

I think what you guys have done is not only great compared to DIY projects, but actually better than the commercial tap tempo trems out there in terms of features. The only small fret I have is if the use of the LDR is going to smear some of the subtleties of the different waveforms out. But I think this is one of the coolest DIY projects so far.

Right now the phase is not reset on a multiplier change. The speed just starts increasing right at the point where you changed it. This does indeed throw the sync out of whack.

You don't have to use a LDR for this! The LDR is just an easy way to do it. You could definitely convert the PWM to an analog LFO and use something more linear, like a OTA, for the VCA. The chip's not the limitation in that case.

I am definitely happy with my PIC LDR trem, but a more linear one might be useful. I think I said something to you similar to that in a PM a while back, that the LDR does tend to mush up the nice waveforms from the chip...




Oh and Tom, I think it would be useful to include this in the datasheet: That you can alter the rail-to-rail voltage on the PWM output simply by buffering it with a digital buffer/inverter that is hooked up to different supply voltages. For example, getting a LFO centered at 4.5 volts would be as simple as putting the 0-5V PWM into a 9V supply inverter and filtering the output of that... then you have a 0-9V LFO. So you don't need offset cancellation op amps in the output stage.

Also, voltage dividing the output of the inverter/buffer down to GND or Vref (the desired LFO bias) before an op amp filtering stage would eliminate the need for a rail to rail op amp.

Maybe a note that you can flip the waveform around by using a digital inverter as well. Some people may not realize it and find it useful.

Yep, LDR wasn't the only way to go. I had thought about a FET thing at one point, but ultimately couldn't find the time to design a circuit for it so I just went with the LDR. We'll soon see how much of a problem it is, if at all. It's probably no big deal.

Quote from: Taylor on February 06, 2010, 08:01:56 PM
Yep, LDR wasn't the only way to go. I had thought about a FET thing at one point, but ultimately couldn't find the time to design a circuit for it so I just went with the LDR. We'll soon see how much of a problem it is, if at all. It's probably no big deal.

The LDR is definitely alot simpler and it does a perfectly good job. There's not too much incentive to go with the more complicated version.

Quote from: JKowalski on February 06, 2010, 07:49:40 PM
Oh and Tom, I think it would be useful to include this in the datasheet: That you can alter the rail-to-rail voltage on the PWM output simply by buffering it with a digital buffer/inverter that is hooked up to different supply voltages. For example, getting a LFO centered at 4.5 volts would be as simple as putting the 0-5V PWM into a 9V supply inverter and filtering the output of that... then you have a 0-9V LFO. So you don't need offset cancellation op amps in the output stage.

Also, voltage dividing the output of the inverter/buffer down to GND or Vref (the desired LFO bias) before an op amp filtering stage would eliminate the need for a rail to rail op amp.

Maybe a note that you can flip the waveform around by using a digital inverter as well. Some people may not realize it and find it useful.

Yes, thanks. That's a good point. There's a nice example of something similar in the Juno 106 synth, where they use a simple transistor to control the sub-oscillator level. Since the SubOsc is a digital signal (a square wave) you can feed it directly to the base of the transistor, and then put a varying voltage on the collector to control the amplitude of the output pulses. Very clever.
I don't think there's any need for a rail-to-rail op-amp. At least, I never used one. But I did have +/-15V rails, and was only looking for a +/-5V output, so that isn't very demanding. With a 9VDC supply, I can see that you might want to push it closer to the rails. Still, it isn't essential.

Tom

Hey fellas, I've got the chips, got the prototype PCB, and built up a prototype. After some fiddling and head-scratching, I sorted out the ticking problem, so it's now working as it should.

This is a great, great trem. It gets a really nice throbby sinewave (most trems have a triangle wave as the smoothest LFO, which doesn't get quite as throbby as a real sine), and an excellent choppy square wave. My concerns about not getting choppy enough are totally unfounded - using the Wave Distort knob allows you to slice the square down to the tiniest blip, which makes for an amazing stuttering fast trem that I was never able to get with any of the other trems I've built (all the usual suspects, Trem Lune, EA, Heartthrob...). The up ramp wave works great before a distortion to get a raunchy swelling industrial kind of sound.

So even not considering the "main feature", this is my favorite trem I've built or heard. And then of course, it's tap tempo!

I haven't had a chance to mess with the "next multiplier" step switch, or sweeping through multipliers with an expression pedal yet. I'm going to put it through a lot more testing, to make sure everything is as it should be, then pretty soon the PCBs should be ready to go.

I'm using an NSL-32 optocoupler. It seems to do the job without ticking.

oh man! i can't wait

Very cool, great news.

Amazing work - thanks!!!  Do you think you'll be able to offer a pcb and programmed chip once the project is finished?  If so, count me in for sure.

Yep, I'll sell the chips for $5 (my cost) along with the PCBs. I had to order a second round of prototype boards because of a few changes I made, so at this point we're looking at 3 weeks until the PCBs can ship.

Somebody had asked me via PM to update what's up with this, so...

The PCBs have been ordered as of today. I went with blue soldermask on these, just for fun. I am a bass player mainly, but today I borrowed my dad's '60 Strat and tried it out to see how it does with a much weaker signal - sounds excellent. I can confirm after quite a bit of testing that this is the best tremolo I've played. The square wave with a really narrow pulse width is awesome. If you've heard Aphex Twin's tune "Mont St. Michel", this is the only trem I've heard that can replicate the ending where the  pulse width gets narrower and narrower until the whole track just about disappears. The coolest thing is going to be putting exp. pedal outputs for everything - expression control over wave distort would be a really nice performance feature.

So, since the boards are now on the way, if anybody wants to order now, they can. Boards will be $13 and the chips are $5. Shipping is $2 to the US, $4 to the rest of the world, and 50 cents for each additional board. I'll be making up the build PDF in the coming days, including parts list. Boards should start shipping in 10-14 days.

Great news, I'm really looking forward to the pdf to see how all the features have come together.

Well, it has 5 knobs. Depth, multiplier, waveform, speed, wave distort. You can preset the wave distort to 50% duty cycle with 2 resistors if you don't want that control. Then there's the bypass switch (regular 3PDT true bypass), the tap switch (SPST momentary), and if you choose, the multiplier step switch (SPST momentary).

There are spots for 3 trim pots internally. 1 for each LED and 1 for the gain of the final opamp stage. Some people might want to bring this gain control to the front panel. I don't have that on my 2 prototypes I've built, but it's easy to do if you want to adjust gain to make up for changing average gain when using narrow pulse widths. The LED trims allow you to trim the current to the OPTO and the visible LED, which cuts out ticking while still allowing a bright LED. I'd recommend a superbright LED for this. You can of course just put in fixed resistors in all 3 trimpot areas if you like.

The tap switch does reset the wave to the beginning, so you can tap it once on a beat to get it back in time if things start to drift. There doesn't seem to be a pop or click when changing multipliers or waveforms, so you can probably do this with an expression pedal while playing with problem.

Very glad to see this nearing completion, Taylor. Well done for getting it there.

Regards,
Tom

Hey fellas, the moment has arrived.

(http://img220.imageshack.us/img220/8056/taptempotremolopcb.th.jpg) (http://img220.imageshack.us/i/taptempotremolopcb.jpg/)

Boards are here. I will have the full document up in the next few days with a description of all the features, the final schem, bill of materials, wiring diagrams, etc. I'll post the bill of materials in the following post so you can start getting your parts together. Mouser part numbers will be available for the more obscure parts.

To get a board and a chip, see here (http://www.diystompboxes.com/smfforum/index.php?topic=83423.0).

Here's the BOM. Let me know if you see something wrong or that doesn't make sense.

Tap tempo tremolo
Bill of Materials

Part type
   quantity - part       (Mouser part number where available, additional info)

ICs
   1 - Electric Druid TAPLFO
   1 - TL072       (dual opamp)
   1 - 78L05       (5 volt regulator)

   1 - 14pin IC socket
   1 - 8pin IC socket

Transistor
   1 - 2N3904       (NPN transistor)
   
Potentiometers
   5 - B10K       (if you're not using the Wave Distort knob, you'll only need 4 B10K potentiometers.)
   1 - A25K       (Optional. This is for an external gain knob if you want one)
   3 - 22K trimpot       (Strongly recommend you use Mouser part# 652-3362P-1-223LF. Other trimpots may be difficult to fit.)

Resistors
   3 - 10K          (if you aren't using the Wave Distort feature, you'll need 2 more 10k resistors, for a total of 5)
   4 - 1K
   1 - 3K6          (3.6K)
   2 - 1M
   1 - 10R          (10 OHMS)
   2 - 220K
   2 - 100K
   
Diodes
   1 - 1N4001
   1 - LED       (superbright blue is ideal)
   
Capacitors          (cap types are just suggestions)
   7 - 100NF (.1UF) film
   2 - 1UF film         (Mouser part# 80-R82DC4100DQ60J)
   1 - 330NF film

            NOTE: all film caps are intended to be boxed metal film caps. Other cap types will not fit.

   2 - 22PF ceramic
   1 - 330PF ceramic
   1 - 10UF electrolytic
   1 - 100uf electrolytic

OPTO
   1 - NSL-32 is recommended. If using something else, look for around 500 ohm ON resistance, 500k OFF resistance.

Switch
   1 - Momentary SPST stomp switch for the tap function, labeled "TAP SW" on the board. If adding the Multiplier step switch, you'll need a second momentary SPST.
   1 - 3PDT stomp       (bypass)

Crystal
   1 - 20 MHZ crystal, labeled "XTAL" on the board. (Mouser part #815-ABL-20-B2)

How is the noise on this build? If you have your amp super cranked can you hear the LFO bleed through? I love my tremulus build but haven't been able to solve that annoyance.

I'm not sure yet. I haven't had my 100w amp dimed while using the trem, but at tolerable home levels I don't have a problem with noise.

my final question b4 buying one - can it do softer fender style tremolo as well?

I don't have any experience with a Fender amp, but with the sine wave and low depth, this gets very smooth and creamy.

Thanks for the BOM!  :)

can taylor, electric druid, jkowalski or anyone else recommend some good reading for microcontroller programming?  especially as related to audio and/or control signals?

also, any programming software or hardware interface suggestions?  any for mac?

I don't really know much about microcontrollers, but have you seen this (from the Digital & DSP section of this site)?

http://www.diystompboxes.com/smfforum/index.php?topic=42476.0

I can offer a decent amount of help with the FV-1 DSP chip, but if you're wanting to do digital control of analog signals like this trem project, I probably know about as much as you do about it.

thanks taylor, there's plenty there to start with.
it would be rad if someone who programmed one of these PICs could lend a hand!  i'm interested in the process...

Ok, the build PDF is done, have a look:

http://www.aronnelson.com/gallery/main.php/v/Taylor/

Any comments on things that are unclear, wrong, misspelled, etc. are welcome.

Great work Taylor.

One question. Electric Druid's diagrams and .pdf order the wave forms in a different order than you described. It would be helpful to know precisely the order of the wave forms - especially which way they go. Does it progress clockwise from '0' to '10' on the pot from 'a' through b, c, d, e, f, g and h, waveforms, or from '10' to '0'... I might be the only one confused, but if I were to make my graphics and then fire up the pedal and find out the waveform knob doesn't match the graphics... I guess I'm asking you to make it really, stupidly, obviously easy to understand that function.

Thanks bud, you've done a super awesome job on this one, and I think it's gonna be a fabulous build! I got two boards after all, and I'm willing to get more to make for other guitarists if they're interested.

Jacob

Looking at the documents, I'm pretty sure what I wrote matches Tom's documents and picture of the waveforms (one exception I just noticed is that I forgot to mention the random step waveform, which is included).

It may be confusing because I called some of the waves by different names.

Hypertriangle=sweep
inverted hypertriangle=lumps

So, from 7-o'clock on the dial, moving clockwise to 5-o'clock on the dial, the waveforms are

up ramp
down ramp
pulse
triangle
sine
hypertriangle (sweep)
inverted hypertriangle (lumps)
random

Can you point me to where I have it written differently, I can't find a spot where it's different? I know the formatting is a little hard to read; all my formatting was lost when converting to PDF - though I'm not a total idiot and have the full Adobe suite, I still can't figure out how to really work with PDFs. I'll hopefully fix this in the coming days, but I'm swamped right now and just wanted to make sure the info was there.

The different names and leaving out the last one was I guess the differences. A closer look puts them in the right order, but I guess I thought the Lump and sweep were the first in the list. The clearer description you just gave helps a lot though, and not just me I hope.

Jacob

http://www.mstracey.btinternet.co.uk/pictutorial/picmain.htm

That one was the first tutorial I read and it really helped me get the basics down. From there, I kept learning by looking up functions that I find and don't understand, analyzing snippets of code that other people have written to do specific things and figuring out what makes them tick, going through completed code and analyzing the program as a whole, and the odd specific tutorial.

I found that once you know how everything works in a very basic sense you can easily learn ASM by simply building on your knowledge through experience. Analyzing someone else's code is a great way because you get introduced to functions you have never used before quite often, and rather then simply learning functions you can learn how a program is put together to make it streamlined and efficient.

I find that coding ASM is less of a cut and paste kind of deal, and more of a logic problem. You have limited functionality in the language, so to solve complex problems you have to use the language in creative ways.


Buying a programmer is well worth the money, don't be hesitant on that if you really want to learn code. Mine was a USB powered, serial port data programmer for only ~$14 and that has served me very well.





And remember if you want to reverse the order of the waveforms just reverse pins 1 & 3 on the pot  :icon_biggrin:

Does anyone have soundclips of this? I'm about to order the PCB, but I'm still a bit on the fence.

I doubt it. I think JKowalski, .Mike and I are the only ones who have built them so far, and I don't know about the other guys but I don't really have a recording setup right now.

However, I will refund the price of the board to the first person who builds one and records sound clips.

Quote from: svstee on April 01, 2010, 07:02:46 PM
Does anyone have soundclips of this? I'm about to order the PCB, but I'm still a bit on the fence.

I posted some sound clips when I built the original tremolo based on the chip from which the tap tempo chip evolved, and from which the schematic for the tap tempo tremolo evolved. As far as I am aware the wave shapes are identical between the two chips. The circuit is also practically identical to the tap tempo tremolo circuit-- my original version just doesn't have the tap features.

The audio path is practically identical to that of the Tremulus Lune except that I used film caps for the input and output caps instead of electrolytic. If you like how that sounds, you will like this. The only difference is the LFO (and it is a big difference due to the flexibility of the PIC LFO), and of course the tap feature.

Anyway, here is my original topic with some sound clips, along with visual representations of the waveforms and wave distort feature: http://www.diystompboxes.com/smfforum/index.php?topic=77471.0

I don't remember if the clips are any good, so take them with a grain of salt. Still, I hope that helps you decide, and I hope you decide to get one. :)

Mike

Does anyone have any input on potentially using rotary switches for waveshape and multiplier?  I'm thinking use a 1P8T (e.g. for waveshape, 1P6T for multiplier)) with maybe 1k resistors between each throw, and then connect the first and last throws to the outside lugs of the pot connections, and the pole of the rotary switch to the middle lug.  Would that work?  It looks like it's just a voltage divider, so I think that would work...  The only thing I'm concerned about is where the ranges actually fall, and if I'd be riding the line between voltages the chip is looking for rather than landing in the middle of the range.  I might need a 470ohm on the end to make the voltage fall in the middle of the range, I'm not sure.  And I don't think it'd be a problem for it to be less than 10k total resistance, but I could always choose resistor values that put it there if needed.

I was thinking this switch: http://www.smallbearelec.com/Detail.bok?no=477

Any thoughts?

Tom has directions for that in his datasheet:

http://electricdruid.net/datasheets/TAPLFO2Datasheet.pdf

Doh!  Thanks for pointing that out.  Apparently I stopped reading the datasheet before I got to that point...

For those building the project, I've started a thread for questions about building it, build reports, etc.

http://www.diystompboxes.com/smfforum/index.php?topic=84020.0

Hi,

made my own tap tempo tremolo inspired of course by the things which have come up here.;)
(http://www.imagebanana.com/img/9w4jnauw/thumb/DSC01860.JPG) (http://www.imagebanana.com/img/9w4jnauw/DSC01860.JPG)
It's fully working and nearly total smd.:P
(http://www.imagebanana.com/img/u7ajm450/thumb/IMG_0515.JPG) (http://www.imagebanana.com/img/u7ajm450/IMG_0515.JPG)
http://www.youtube.com/watch?v=wmI9JOuNjQU

Cheers

Very nice, would love to see the trace side of the board if you don't mind sharing it. Which control did you leave off?

has anyone suggested using this new TAPLFO thing to do phaser, wah, and other mods?

Do you mean, has anyone come up with a schematic for one of these? AFAIK no. The reason tremolo was so easy is that the output of the TAPLFO puts out a PWM signal, which needs to be filtered before it can be used as an LFO. The optical tremolo is slick because the LDR simultaneously accomplishes the filtering (by way of its slow response) and the actual amplitude modulation. So to do one of these other effects you'd need to deal with that in a different way. A PWM phaser would be quite possible, I believe Nelson did one awhile ago.

The other thing is that tap tempo has diminishing appeal for some other effects to many people, myself included. Rhythmic delay and tremolo make sense with the way most people use these effects. But personally, for phaser/flanger/filter type stuff, I like slow sweeps that aren't tied to the tempo of the music.

Quote from: aziltz on April 22, 2010, 12:06:49 AM
has anyone suggested using this new TAPLFO thing to do phaser, wah, and other mods?

I'm sure it would be easy enough to incorporate it into a twin-t wah, like the Colorsound Inductorless. In fact, R.G. suggests it in his Technology of Wah Pedals (http://www.geofex.com/Article_Folders/wahpedl/wahped.htm#messing) article.

:)

Mike

Yep, and a little bit higher on that same page RG has a remote wah schematic that would let you control a regular inductor wah using the TAPLFO with an optocoupler as well. A vibe circuit like the Neovibe would also be quite doable since it's already optical.

Taylor, is there a schematic of the full Tap Trem circuit posted?

Yep:

http://www.aronnelson.com/gallery/main.php/v/Taylor/

Quick question re: pot orientation.

Should the pot wipe from 0v - 5v in a clockwise direction?

Andy

Yes, counterclockwise is 0v.

I would like to reset the phase of the LFO when pushing the bypass switch. What would be the easiest way to generate a negative going pulse to reset the LFO by using one pole of a 3PDT foot switch?

Thanks for your help in advance!  :)
Ah, and sorry if this was already discussed....

Peace,

Markus

I'm wondering why I can't download the PDF'S from the gallery? I can't download any PDF'S from the gallery for that matter...

Could someone e-mail me it?

Please?

seandavidharris@gmail.com

Thanks in advance...

Aahhhhh...GOT IT NOW.........

Yeah, the PDFs are akind of hidden on the page...

Quote from: markusw on May 31, 2010, 07:19:58 AM
I would like to reset the phase of the LFO when pushing the bypass switch. What would be the easiest way to generate a negative going pulse to reset the LFO by using one pole of a 3PDT foot switch?

Thanks for your help in advance!  :)
Ah, and sorry if this was already discussed....

Peace,

Markus

Hey Marcus, somehow I didn't see this when you posted it (I do think I was moving my house at the time, guess that explains it).

You'd have to build a logic circuit to turn a stage change into a pulse. I'm not positive how to do that honestly, as I'm just learning logic myself. I will be getting my copy of The Art of Electronics in a day or 2 hopefully, and if you're still interested in this, post again in a few days to remind me and perhaps I'll have an answer for you.

But, did you know that tapping the tempo switch once resets the oscillator phase? It's not quite as elegant, but basically you can do what you want by hitting both the bypass and tempo switch when turning on the effect.

Quote from: markusw on May 31, 2010, 07:19:58 AM
I would like to reset the phase of the LFO when pushing the bypass switch. What would be the easiest way to generate a negative going pulse to reset the LFO by using one pole of a 3PDT foot switch?

Thanks for your help in advance!  :)
Ah, and sorry if this was already discussed....

Peace,

Markus

It's really easy. You don't need any extra components. The "negative going pulse" needed to switch inputs on the chip just means that whenever the voltage on that pin goes to zero after being at 5V then it will trigger. If you put a square wave on the pin, it will trigger at every time the square wave transitions from 5v to 0v. I assume you don't care about the bypass being reset when the effect is turned OFF, only when it is turned ON, so if you hook up an extra pole on your bypass switch (you can use the LED switch pole on a 3PDT for this too, serves two purposes, but remember if you do this to use the 5V supply for the LED not the 9V) to put a 5V on the pin when the effect is OFF and GND on the pin when ON, turning the effect on will trigger the 5v->0v negative "pulse" and reset the phase.

EDIT: ah sorry I'll work it out for you tomorrow morning. This wont work since you need to be able to use the tap tempo button along with it.  :icon_rolleyes:

I'll give you a hint though, to generate a  pulse use a decoupling capacitor to block the DC component of the square wave "state change" from the switch.

In the interest of keeping it simple here is something to try, rendered in lovely MS paint-o-vision:

(http://i34.tinypic.com/so9wt0.jpg)

Gives a negative pulse whenever you

A: switch the SPDT switch to 5V

B: Hit the SPST momentary

Also incorporates the "effect on" LED.

The capacitor and the resistor to ground determines the length of the pulse. The MOSFET drain resistor can be almost anything, maybe 100k

Hey that's very slick. I simmed it and it works just as you say.

Just a tip, if you want to save outboard wiring, the outside lugs connect to +5v and ground, so you can actually wire lug 3 and lug 1 of any of the pots (except the multiplier pot) to the board and tie them to the corresponding lugs on all the pots. I did this and it worked great and really used a lot less wire.

Ok, maybe this has already been answered, but I can't see it anywhere in this thread, and this thread is LONG!
I was just wondering if it is possible that the tap tempo could control the repeats on something like the PT80 delay?
I'd also like to have a dedicated square wave output for 16ths  so that I can control a vanishing point.
Is any of this possible?

this tap tempo can't be used to control a PT80, but there is a kit in Aron's store (link at the top of the forum page) called Taptation which can add tap tempo to any PT2399 based circuit. I'm not sure about the square wave output, but thought I'd answer the question I knew :)

Barcode80,

Just to clarify, you can connect all of the #1 lugs and all of the #3 lugs on the pots together and just connect to one of the pot contacts on the board, with the exception of the multiplier pot?  I'm assuming an external volume pot is excluded from this as well?

correct, I was referring to the standard build with the internal trim for volume. The same does not apply to that pot.

Quick question, is the momentary switch for the tap supposed to be normally open or normally closed? I'm using a normally open, and it seems the tap tempo is running off the travel back up from my tap instead of the actual tap. Thoughts?

It should be normally open, and closing the switch grounds the tap pin. Are you sure your switch is NO?

Quote from: Taylor on October 10, 2010, 10:53:42 PM
It should be normally open, and closing the switch grounds the tap pin. Are you sure your switch is NO?

yep, but i'll double check. I'm using a batch of momentaries I got in a salvaged MXR micro controller, and I think they were all normally open, but I'll double check.

are the boards and chip sets still for sale?

Yep, PCB thread is here:

http://www.diystompboxes.com/smfforum/index.php?topic=83423.0

I've also setup a website to make ordering easier:

http://musicpcb.com