Building the tap tempo tremolo

[Taylor]

Here's the thread that started this project going.
Here's the build document.
PCBs are here.

I have received some emails with questions about the project so I thought it would be a good idea to start this thread to have these questions and answers available to all who might be wondering.

I wasn't sure about the orientation of the NSL32 - can you help me understand how to orient that?

The optocoupler orientation goes like this: the LED side is the one with the short legs, the resistor side has the long legs. The resistor orientation doesn't matter, just like a regular resistor. The LED does matter. The negative side is the one indicated by a little white dot. The PCB has a + sign next to one of the pads, obviously put the positive (non-dotted) side here and the dotted side next to it. Then feed in the resistor-side legs.

I don't know about the dot you're talking about. Mine doesn't have one at least. One end, I think it was the short lead side, has writing on it. The other is glossy smooth. I have the writing side on the + side of the PCB. Is there a way to measure with my DMM?

I believe you have it in wrong. The end with writing on it is the resistor side. The glossy side is the LED, and the dot marks the negative LED lead.

Are you sure you've got an NSL-32? They should all have the white dot. As with all things, the datasheet reveals much:

http://www.alliedelec.com/Images/Products/Datasheets/BM/SILONEX_INC/Silonex-Inc_Actives-and-Passives_6995014.pdf

There is a way to check with a DMM, but it's convoluted. Connect 9v to a 10k pot's center lug, and connect one of the short NSL-32 leads to one of the outer lugs of the pot. Connect the other NSL-32 lead to ground. Put your DMM in resistance mode, in the 200k setting, and put a DMM lead on each of the long leads. You should have some resistance. If the resistance you measure varies by turning the pot, then the short lead connected to the pot is the positive one. If there's no resistance, or it doesn't change, then flip the short leads around and try again until you can make the resistance change by moving the pot.

Now, that's a pain, so I'd recommend first verifying that you have the right optocoupler, and trying to figure out why there's no polarity mark on it.

[jmasciswannabe]

Is there a pot recommended for the wave distort that would make it easier for separating the wave types or is it fairly obvious....I haven't built it yet. Doing parts order now. I was thinking it might be hard to cram all those symbols around one pot. Or is there a way to instead wire up a selector switch with resistor values that would correlate with the wave...for example 1k=ramp up, 2k = ramp down...etc 

[jmasciswannabe]

Yup...already asked, found it. Sorry for the hassle.

[Taylor]

Glad you found your answer, but note that wave distort and waveform select are different. The Wave Distort knob definitely should be a pot, not a switch, as it's a continuous control. The waveform select can, as you found, be made into a rotary switch, but I don't find that to be necessary, it's fairly obvious which one you have selected.

Here's a link to the post about making any knob a rotary switch instead of a pot, for anyone else who might wonder:

http://www.diystompboxes.com/smfforum/index.php?topic=80407.msg698237#msg698237

[jmasciswannabe]

Ah, I see. The wave distort kinda acts like the symmetry knob on the lune. I will take your advice on the wave select and stick with the pot. I'm ordering parts tomorrow and hope to get a build report up soon. Also, got the board and parts and all looks well. Thanks! Can't wait to get this up and running!!

[good air]

How would you compare this trem to something like the goatkeeper?  Obviously smaller but seems like it can do a lot with the parts.

[Taylor]

This circuit is without question the most full-featured and versatile DIY trem. But it doesn't do quite as much of the exotic stuff as the Goatkeeper.

[studiostud]

So here's a question.  In the other thread someone asked about using rotary switches instead of pots for the multiplier and waveform controls.  I found the documentation on such but I was wondering how difficult it would be to attach 3mm LEDs to add some wow factor.  Would be sweet if you could use the rotary switch to select between waveforms/multiplier and then also have an LED light up next to whichever position you choose....  thoughts?

[Taylor]

Well, assuming you'd want to keep the available waveforms, you'd need a big switch, or go to electronic switching. You'd need a DP8T I guess, to switch both the voltage dividers and LEDs in 8 positions (6 for the multiplier). Such switches exists, but once you go above 3P4T rotary, it starts getting expensive/hard to find.

Here's one I found just now:

http://uk.digikey.com/1/1/290879-switch-rotary-dp-8pos-enclosed-c2p0208n-a.html

You could also do electronic switching. This would be very complicated. The common CMOS switching ICs I know of are mainly built around a bunch of double throw switches together, so you'd need a SP8T (which is somewhat common) and then maybe 4 4066's I think, and you would connect the enable pins of 2 of the CMOS switches together; one would be for an LED and one for the voltage divider. This conglomeration of one throw of the rotary switch, plus 2 CMOS switches in a 4066, would equal a double pole single throw. So you'd duplicate that 8 times. I guess at that point a $24 switch starts looking reasonable.

[.Mike]

What about using an LM3914 in combination with an SP8T rotary?

It's usually used as an audio indicator, I think. I've never used one, but ten minutes of research indicates that it can be set to respond to a different range of voltages with just a couple of resistors.

Set it up so that the lowest waveform voltage triggers the first LED, and the highest waveform voltage triggers the eighth LED. Use the same CV coming off the SP8T to trigger the LM3914, which lights up the appropriate LED.

Just a thought.

Mike

[FunkyGibbon]

Well, assuming you'd want to keep the available waveforms, you'd need a big switch, or go to electronic switching. You'd need a DP8T I guess, to switch both the voltage dividers and LEDs in 8 positions (6 for the multiplier). Such switches exists, but once you go above 3P4T rotary, it starts getting expensive/hard to find.

Here's one I found just now:

http://uk.digikey.com/1/1/290879-switch-rotary-dp-8pos-enclosed-c2p0208n-a.html

You could also do electronic switching. This would be very complicated. The common CMOS switching ICs I know of are mainly built around a bunch of double throw switches together, so you'd need a SP8T (which is somewhat common) and then maybe 4 4066's I think, and you would connect the enable pins of 2 of the CMOS switches together; one would be for an LED and one for the voltage divider. This conglomeration of one throw of the rotary switch, plus 2 CMOS switches in a 4066, would equal a double pole single throw. So you'd duplicate that 8 times. I guess at that point a $24 switch starts looking reasonable.

You could also use two 4051s to give 2P8T, instead of four 4066s, to save some space and complexity.

However, I also like the idea of using an LM3914 with indicator LEDs. I wonder if one could use the pot method with this instead of a rotary switch. The LM3914 seems to have "dot mode" which I think means the LEDs turn on one-at-a-time, rather than as a group with the brightest in the centre. I need to do more reading on this.

Christopher

[thedanielwilliams]

I partially completed my TTT last night (no switches) and am pretty pleased with it. I tuned out the ticking as best I could, but I then had trouble getting to unity gain. Would it be possible to bring the gain trimpot outside and replace it with a 50k audio pot for more volume?

[Taylor]

Yep, that's certainly possible.

[Taylor]

Somebody posted this over at Electro-Music.com, thought it was really cool so I'm posting it here:

Finally got around to building this. Fun to play around with but most of the wave forms don't affect the amplitude as much as I hope. I've modularized mine so I can get more use out of it.

My feet are kinda big so I had to stick the stomp switch up top so I could avoid hitting the tempo and multi switch.

[thehoj]

So, like an idiot I did something wrong when I went to solder everything up.. I put the 22k trimpot in the gain location when I was actually wanting to put the gain knob external, so I desoldered the trimpot and pulled it out and it took off the pads on the top of the board.. Looks like two of the pins for the pot have traces on the bottom, but then one of them has a trace on the top, going to the tl072.. Looks like pin 7.. Just want to confirm that I should just run the wire from my pot directly to that pin.

[Taylor]

Hmm, that's a tough one. Perhaps I need to do a tutorial on desoldering from double-sided boards?

The issue here is that that pin of the trimpot connects to pin 7 of the TL072, and also to the 330p cap and 1uf cap. The pad lies between the connection of the opamp and the caps, so you've severed not just the connection to the trimmer, but the connection of the opamp to the caps. You'll need to run 2 wires from that pin of the trim: one to pin 7 of the opamp and one to the caps. Look to the schematic to be sure you're correcting these properly.

[thehoj]

I'm having a bit of a hard time using the schematic to verify this..
What I have done so far is on the new pot I'm using, I've wired (looking at the back of the pot) the lug on the left and the wiper directly to one of the pins on the nsl-32 (where I could see the trace running on the back for those two connections of the trimpot), and then I have the right lug wired directly to pin 7 on the tl072. You're saying I should jumper from that right lug on the gain pot to the 330p and 1uf cap also? Which pins on those two caps?

Also, what is the correct orientation for the rest of the pots if I'm looking from the perspective of the back of the pot.




Really appreciate it.
vvvvvvvvvvvvvvvvvvv

[Taylor]

Tomorrow I'll post some images here to help answer both questions.

[Taylor]

This shows better than words how that pot is connected, so it should show you how to wire everything. The bottom layer is blue, the top is red.

I didn't have time to take a picture of the pots, but looking at the board so you can read the silk screen, the clockwise lugs go to the left, and ccw to the right.

[thehoj]

Cool.
Just to be 100% clear on pot orientation, are you saying clockwise and counterclockwise looking at the back of the pot with the lugs facing up?