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This is on the breadboard right now. I don't usually release a schematic before I've soldered up a working pedal, but I know Jimi Photon was looking for a vactrol implementation of the Harmonic Tremolo.

(https://dl.dropbox.com/u/9878279/Cardinal%20Tremolo.png)

The Cardinal Tremolo is a vactrol implementation of the Harmonic Tremolo from Fender's 1960-1963 tremolo-equipped amps (the Super, Pro, Twin, Showman, and Concert models). A huge amount of credit for the basic design of this effect for stompboxes goes to RG Keen, who created a FET-based implementation. This vactrol-based implementation has some nice benefits, not least of which is that parts matching is not required, and it uses a far simpler chip-based LFO (or the TAPFLO chip). Additionally, the topology allows a simple switching mechanism to go between the harmonic tremolo and a "normal" tremolo.

How It Works
Input stage
Your input signal is amplified by a simple FET gain stage (drain follower). It's got enough gain for a fair-sized boost. This is to make sure there's enough output in cases where you might have a really hard wave form (for example, a distorted triangle wave in the TAPFLO chip), without the necessity of a fourth gain stage. The gain stage before, rather than after, just worked better, epecially with the tremolo mode used for Q2. J201 was used because it had more output, but other FETs are perfectly fine, perhaps with some necessary rebiasing, for anyone who doesn't need or want as much output volume. In general, I used FETs because BJTs were too bright (and had an unpleasant harshness), and because they require additional biasing resistors. If FETs become prohibitively expensive, I might decide to redesign it, but the J201 is still plentiful and cheap.

Q2 tremolo section
Q2 serves two functions. When the switch is in harmonic tremolo mode, C8 is connected to ground, and together with R4 creates a low-pass filter with a cutoff of 723Hz (which sounded best to me after a LOOOOOT of fiddling). When the switch is in "normal" tremolo mode, C8 is no longer connected to ground and for all intents and purposes Q2 becomes an all-pass stage. The 10K at the input cuts a very small amount of highs, but that's cured by the 1uF bypass cap on the drain. The gain on Q2 will pretty much always be very close to that of Q3. I tried a large number of J201s and they all biased just fine into this rage. J201 was chosen, again, because it had enough gain to ensure that the effect is always at or above unity volume.

The actual tremolo effect is created by putting the LDR in series between two 1uF output caps. When the LED is on, the resistance between the two caps drops and the signal passes. When the LED is dark, the resistance is high enough to block all signal. This is the same as the tremolo method used in my Blue Warbler, and it's also similar to the method used in the Tremulus Lune. I used this method on the all-pass stage to ensure that it would work properly with LFOs that expect the series LDR. (Again, my intention is to build this with the TAPFLO chip.)

Although my testing showed it was not necessary for a working and good sounding effect, you can adjust R7 and/or R5 to make sure the level of Q2 does not overwhelm Q3. I tried all the J201s I had and none of them varied enough in their gain to not produce a phasing sound.

Q3 tremolo section
Q3 is set up essentially as a treble booster. Very, very small input and output capacitors pick up, for the most part, where the low-pass filter on Q2 leaves off. There is a small amount of overlap, and the output capacitor is also slightly interactive with the output of Q3, so the 1nF is a compromise (2.2nF would have been ideal for the harmonic mode, and 470pF would have been ideal for the "normal" mode).

The tremolo in this section is accomplished by placing the vactrol between gate and ground. This means it works backwards from Q2. Here, more "on" time shunts more signal to ground. The result is that this section is at full volume while Q2's is at minimal volume, perfectly out of phase with each other.

The mode switch grounds the gate of Q3 in "Trem" mode, shutting it off. It was done this way because it made the mode switch a very small and common SPDT switch.

LFO
The LFO can be any capable of driving multiple LEDs. I picked the LFO from CultureJam's Shoot the Moon (a simplified Tremulus Lune) for the example schematic because the LED will spend more time "ON" at lower depth settings.

The TAPLFO chip from Electric Druid will function the same way.

There are probably other LFO implementations that will work. For example, you could use the simple phase shift oscillator from the Magnavibe (also used in my Blue Warbler) by hard wiring the depth to max, and using a blend circuit to bypass the whole effect, but this won't really save many parts (if any) because you need the extra gain stage for the mixer in addition to the LFO parts. You can't just wire it up as normal, though, because the depth pot will not work right.

VERY IMPORTANT NOTE: To function, this effect REQUIRES the VTL5C1 or another vactrol (or LDR) with dark resistance >30M. Smallbear sells a Macron clone of the 5C1 (http://www.smallbearelec.com/servlet/Detail?no=1296), and the CdS photocell 9203 (http://www.smallbearelec.com/servlet/Detail?no=711) MAY work.

The mode switch

As noted, the mode switch goes from the harmonic tremolo sound and a normal full-range tremolo by removing the treble cut from Q2 and grounding out Q3.

If you use a center "off" switch, you'll also get a third "Vibe" (or maybe "bright" would be a better description) mode, which removes the treble cut from Q2 but leaves Q3 on. This means that during most of the cycle, the high frequencies will pass unhindered, while the lower frequencies throb. Although it doesn't really sound like any particular vibe unit, it does add some variety, and I couldn't think of what else to call it. It's also a neat effect for playing notes over open strings, so the low notes will have a noticeable tremolo effect applied while the high notes will cut through better.

SNEAK PEAK VIDEO!


Enjoy!

I'm actually going to be building myself a version using the TAPFLO chip, which I've already confirmed works for this design. Unfortunately, I fried my chip doing something stupid and had to order another from Smallbear, so I won't be able to build it for a bit. I'll try to work up some layouts soon, one for the TL072 LFO and one for the TAPLFO. In the meantime, I need to build the other stuff I put on hold to get this designed. :)

EDIT EDIT: Vibrato mode is a no-go. Doesn't work without a lot of contortions and severe watering-down of the circuit as a whole.
Vibe Mode addition mod

It's possible to add a true pitch vibrato mode, by turning the full-range stage into a Magnavibe stage. It requires a few changes and a DPDT SPST switch: the LDR needs to be connected to the source instead of C5; and then a 10nF cap needs to be connected to C6. Like this:

1  4
2  5
3  6
EDIT: Simplified
1
2
3

1: Source Drain of Q2
2: C5
3: No connection
4: 10nF (other side is connected to the drain)
5: C6
Change C5 to 10nF. With this implementation, the tremolo on Q2 is created simply by shunting the connection of C5 to C6, meaning that the tremolo function is a source follower instead of a drain follower. Once you've made the drain and source resistors match and bumped them up to 10K or 22K, it's largely irrevevant which pin you pull the tremolo from because you won't get much of a boost either way. 22K is a value I know works great with a 2n5457, but I'm not certain about with a J201.

However, you would also have to omit C4, and change R5 and R7 to a matching value (not sure about the exact value -- 10K or 22K would probably both work -- but they have to be identical). The gain on Q3 would need to be changed to match, perhaps by putting a 1K (just a guess on the value) on the source instead of grounding it.

Optional added craziness for use with center off toggle: 56K resistor from lug 3 to lug 1. You'll get a sort of chorus-y, half vibe effect. I suspect that, combined with the harmonic section turned on that this can create some really, really unusual sounds.

holy sheet, jon, this looks fantastic!!!

thanks man!! sounds like EXACTLY what the doctor ordered!

i will start laying it out tomorrow i hope.

so no home-rolled vactrols? i guess i can buy a couple from steve. ;)

thanks man... this looks pretty good and accessible!

we'll see how vero-friendly it is. ;)

Nice job Jon. I like the TAPFLO implementation, even if (or perhaps because) it is a bit of an anachronism.
You might get away with using 'typical' LDRs if you drop R5 a fair bit. You will lose a little bit of boost and it will not go as deep, but it might work well enough all the same.

Quote from: samhay on March 07, 2013, 08:51:03 AM
You might get away with using 'typical' LDRs if you drop R5 a fair bit. You will lose a little bit of boost and it will not go as deep, but it might work well enough all the same.

I'll try that, but off the top of my head I'm not sure it'll help. The equivalent resistor is 2.2K in the Blue Warbler and won't trem with anything else* there either ... not even a little bit. Common sense tells me: "Well, 10M or 1M should be high enough to block most signal just as well as 50M," but that doesn't appear to be the case. Maybe it has something to do with the vactrols' light memory. Part of the problem is I don't really understand exactly why it works in that orientation in the first place. Originally I did it in the Blue Warbler because of the series LDR arrangement in the Tremulus Lune, and only later discovered that no other vactrols work. Most of the time I arrive at circuits by trying literally everything I can think of on the breadboard, so it's hard for me to know how to change some things once I know they work.

Considering that the VTL5C1 also has the really low light resistance necessary for tremolo on Q3 (actually, the low on resistance is almost as rare in roll-your-owns as the high dark resistance), I'm not too torn up. It's a pain to have to order a specific part, I know, but

*Incidentally, H11F1 and the like will function, but often they cause distortion. It's better to use the center pin on the diode side if you try to use these chips. The datasheet makes it look like that pin's not connected to anything, but in practice it works. It would be awesome if someone actually manufactured a real honest-to-goodness chip-sized vactrol at a reasonable price instead of all the photodiode/phototransistor nonsense.

Yeah, after posting I looked up the VTL-5C1 and it has a much lower light resitance that I thought it would - very cool.
Upon futher reflection, it would appear that LDR1B is just one half of a voltage divider with the volume pot and C6 is mostly redundant. If you replace the volume pot with e.g. a 10k, you should get away with using an LDR with 10x less dark resistance as long as its light resitance is quite low.

Even if it works badly with a fet optocoupler that's pretty interesting. They can be made to work as voltage-controlled resistors (e.g. http://www.edn.com/design/analog/4368893/Use-a-photoelectric-FET-optocoupler-as-a-linear-voltage-controlled-potentiometer (http://www.edn.com/design/analog/4368893/Use-a-photoelectric-FET-optocoupler-as-a-linear-voltage-controlled-potentiometer)), but they don't get much love in the stompbox world. I thought pin 3 was NC, so using pin 2 is how fet optos work?

Quote from: samhay on March 07, 2013, 09:55:14 AMI thought pin 3 was NC, so using pin 2 is how fet optos work?

Pin 5: http://www.datasheetcatalog.org/datasheet/fairchild/H11F1.pdf
The "FET" side actually appears to be more like a diode than a FET. I was unable to make it work as an amplifier, for instance, which was a real disappointment because that would have been freaking awesome for so many things ... sorry, I realize that saying "diode side" was confusing since I didn't mean the LED side. :)

I can try reworking the output sections. I also noticed this morning that C6 was redundant in a trem-only design :), as I had been keeping the topology from a prior schematic that just had a vibe/trem mode and then changed some values and added Q3.

I'd have to 10x the output caps if I use a smaller volume pot and ditch C8, and it means no hope of a vibe mode, but if it means a wider variety of optocouplers/LDRs, then I'm certainly willing to give it a shot!

the vibe mode may be the coolest part. tremolo kinda vibes sound completely different from chorus kinda vibes.
jon, any chance of a vid or audio snip?
would love to hear this thing before i commit to ordering some vactrols. ;)

Quote from: pinkjimiphoton on March 07, 2013, 11:23:47 AM
the vibe mode may be the coolest part. tremolo kinda vibes sound completely different from chorus kinda vibes.
jon, any chance of a vid or audio snip?
would love to hear this thing before i commit to ordering some vactrols. ;)

I'll try to film something tonight. I had basically spent 20+ hours straight on this by the time I finished the schematic last night and it was too late -- and I was too tired -- to film anything.

I'll just be able to do the basic sound at the moment, so no messing with the LFO except speed. I didn't have enough space on my breadboard for the chip-based LFO without removing all the TAPLFO stuff, so I'm just using a phase shift oscillator until my new TAPLFO chip arrives from Smallbear. I already know that LFO works the way I need, though, because I've built multiple pedals that use it. If I have time, I'll see if I can get the vibrato mode switch up and running (and balanced) first, too.

I think (and I may be very wrong) that if you bump C9 up to 10n and drop the volume pot to 10k then you will still get all 3 modes to work reasonably well.

i hate to ask such a dumb newb question,
but on the schem it shows vactrol a and b.. is that the a side with the dot?
or do i need two of them?
waiting to pull the trigger at small bear...
thanks jon!

Quote from: pinkjimiphoton on March 07, 2013, 03:58:22 PM
i hate to ask such a dumb newb question,
but on the schem it shows vactrol a and b.. is that the a side with the dot?
or do i need two of them?
waiting to pull the trigger at small bear...
thanks jon!

Sorry! I went through a bunch of iterations of this schem for the LFO and forgot to mark it. those are the LDR sides -- the long legs. They are not polarized, just like a resistor. D2 & D3 are the LED sides (the ones marked with the dot or + sign for the anode).

EDIT: Also, video in 1 hour. Uploading now.

awesomer!

thanks, now i know what i needed i think... so vactrol a and b are the two sides, correct?

i'll order from smallbear. ;)

Quote from: pinkjimiphoton on March 07, 2013, 07:08:34 PMthanks, now i know what i needed i think... so vactrol a and b are the two sides, correct?

Yes, the "a" is the LED side, and the "b" is the LDR side. 1 and 2 designate the two separate vactrols. Is it clearer in the updated schem? It'll be really obvious once I finish a layout ... not going to happen till this weekend, though. :)

Some updates in the corrected schematic:
1) Increased the output cap on the input stage (C2). Testing with rested ears showed this to pass all frequencies better.
2) Dropped the 1uF cap between the drain of Q2 and the LDR. Not only does it still work, but it sounds much better.
3) Unfortunately, my attempt to get it to work with a 10K volume pot also failed. It drops the output significantly, and the treble side sounds broken ... really, really weak for some reason. Part of it is the interactivity between Q2 and Q3 -- they seem to sort of reinforce each other's gain if that makes any sense.
4) The vibrato mode a la the Magnavibe is a no-go, so I've crossed out that whole mess in my original post. It dilutes the effect, breaks the treble side, doesn't sound particularly good, and frankly I'd much rather have an excellent sounding harmonic tremolo with a really good "normal" tremolo option than a watered-down pitch vibrato + watered-down harmonic tremolo. The good news is that this means that the effect is back to needing just a SPDT for the mode switch (optional center off for a "bright" mode).

Unless some sort of inspiration strikes between now and the time I build a copy of the circuit to confirm, this is the final schematic. I want to stress that until someone else breadboards or builds it that it's unconfirmed.

Video added! :D

Very basic -- I'll do a better demo after I have a working pedal in hand.

Just in time for the Conclave!  :D

Sounds really good.
Nevermind about the absolute requirement for the vactrol - sounds like it is well worth it.

Hey, folks, here's an alternate LFO that will do a nice true sine wave:
(https://dl.dropbox.com/u/9878279/Backwards%20phase%20oscillator%20LED.png)

This'll give it a mode like a brownface and the other mode will have the "right" wave form. It doesn't get quite as deep as a chip-based LFO so it won't have a massive throb, but it's a decent choice for a simpler build with fewer parts.

holy sheet, jon, this is amazing...thank you sir!!!!!! i am gonna try and work up a vero for this thing, and get to building it as soon as i can get a realistic chance.. thanks !!

this thing sounds like the sounds i hear in my head. ;)

Quote from: pinkjimiphoton on March 08, 2013, 08:29:11 PMthis thing sounds like the sounds i hear in my head. ;)

Yeah, I was poking around in there the other ....



I .... I mean .....

Oh good!



(I need a tinfoil hat emoticon)

careful, lotta black holes in there....   :icon_mrgreen:

I remembered that I had an extra Shoot the Moon board sitting around. So I could stop guessing about the chip-based LFO! I just soldered up the LFO section and left a couple parts unattached so I could use it on the breadboard. The "final" version of the chip-based LFO is shown in the schematic above.

I changed the following: The rate indicator is now also a depth indicator. It's in series with the vactrol LEDs. There are two CLRs following the rate indicator and the first vactrol. This not only "works" but "works a hell of a lot better" ... the depth control was terrible with the stock STM LFO in this circuit. Now it does an almost perfect sine wave -- almost indistinguishable at similar depth levels from the transistor-based LFO -- AND still does hard on-off in square wave mode if you include the waveform knob. The soft waveform is much better than in the original STM, and it saved a part, too.

There is no "real" volume drop between modes. The adjustments would be on the order of a few decibels. This is true now of both types of LFOs.

Oh ... and it looks like I can get the transistor based one in a 1590A on perfboard for sure. The chip-based one is going to take some doing, though.

thanks jon!! i'm glad i didn't start on vero yet...

i got thinking, and another fuzz happened.  ::)

i'll post it soon... but am really REALLY psyched to get to work on this.

hey... how does it sound really slow? does it throb like it does at the higher speeds?
thanks!

Quote from: pinkjimiphoton on March 10, 2013, 10:31:49 PM
thanks jon!! i'm glad i didn't start on vero yet...

i got thinking, and another fuzz happened.  ::)

i'll post it soon... but am really REALLY psyched to get to work on this.

hey... how does it sound really slow? does it throb like it does at the higher speeds?
thanks!

The chip-based one sounds great slow. The chip LFO is just unbelievable now, actually. It can completely bottom out the full-range side, so it's got a HUGE amount of throb and even gets phaser sounds at the highest depth setting. I'm soldering up a perfboard layout of it right now and should be able to have a complete demo before the end of the week (just need to drill a box for it). The waveform control is WAY more useful than I thought it would be. I was going to put it on a trimmer, but now I know I want access to it.

I also made a 1590A layout with the transistor LFO. It's not as good because it can't get as slow or as fast, and can't get as deep, but it's good enough to stick in a little box. No reason to use it with a bigger build, though. It sounds like an EA tremolo, and it's fine for the subtler stuff. It just can't do "crazy."

I'll post both of my perfboard layouts as soon as they're verified.

I figured you weren't starting on the vero layout or I would have warned you. :)

I'll keep an eye out for a stupid pedal tricks. ;)

lol...

yah, and i'm looking forward to your demos and layouts!
i will go for the chip one i guess...
it sounds like it's the one to go for.

keepin' an eye peeled! ;)

These layouts are verified 3/10/13. All schematics have been updated (there were a couple nets run incorrectly, and I adjusted the values on the bias modulated LFO to keep it from crapping out at high speeds.)

Apologies for the handful of small parts, but I really didn't want to have to add another row. Though to be perfectly honest, I can't imagine how many people besides me really torture themselves with complicated circuits on perfboard. There will be a PCB project of this, but I'll wait until that's finalized to announce it.

Perfboard layout for the IC version:
(https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Nonmini%20builds/Cardinal%20Tremolo%20-%20IC%20LFO%20version.png)
PDF: https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Nonmini%20builds/Cardinal%20tremolo%20-%20IC%20LFO%20version.pdf

Bias modulated version in a 1590A layout:
(https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Cardinal%20Tremolo%20-%20bias%20modulated%20%28transistors%29.png)
PDF: https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/cardinal%20tremolo%20-%20bias%20mod%20version.pdf

 :icon_idea: Would it be possible to create a version that uses a CD4007 and one n-channel and one p-channel as variable resistors and use the leftover mosfets as buffers.. this would drop the $10 each vactrols and obsolete FETS and sub it all with a 10c CMOS IC.

Quote from: ~arph on March 13, 2013, 06:55:12 AM
:icon_idea: Would it be possible to create a version that uses a CD4007 and one n-channel and one p-channel as variable resistors and use the leftover mosfets as buffers.. this would drop the $10 each vactrols and obsolete FETS and sub it all with a 10c CMOS IC.

Certainly an intriguing idea ... I'm hopeless with chips for the most part, but if you know a way to work it, I'm all ears. Do you have an LFO implementation using that chip? The dry path is really simple in this version, so it shouldn't be too hard to port the filtering to another amplifier. (I probably could have done it with a TL072 and buffered the output, but that's a lot more circuitry.)

The idea is that the LFO stays the same, but that the dry path and vactrols are substituted with the CMOS ic. Thing is I never worked with this IC either. I just know it's possible to use a mosfet as a variable resistor and that you can use the complementary pairs in that IC as amplifiers. Never done either with this IC, but it should be a matter of putting the pieces together. Btw, I think we still need a buffer JFET as the amount of mosfet pairs in the IC is just one short.

EDIT:

Some references:
http://www.aronnelson.com/gallery/main.php/v/edvard/guitarnoteexpander.png.html (http://www.aronnelson.com/gallery/main.php/v/edvard/guitarnoteexpander.png.html)  <-- This one's good
http://www.uni-bonn.de/~uzs159/vcf4007_s.gif (http://www.uni-bonn.de/~uzs159/vcf4007_s.gif)
http://www.diystompboxes.com/smfforum/index.php?topic=52472.0 (http://www.diystompboxes.com/smfforum/index.php?topic=52472.0)


Oh and if it works out we should call it the White Smoke Tremolo  :icon_mrgreen:

the ancient "eti446 audio limiter" uses the (unbuffered) fet pairs (inverters) in a 4049 as variable resistors. dunno if this is any help, I can probably post the circuit if any interest.

I'm keenly watching this thread, with about no hope of ever getting any real-life vactrols in mind.

located in australia

Quote from: duck_arse on March 14, 2013, 10:45:11 AM
with about no hope of ever getting any real-life vactrols in mind.

Just too expensive, or literally can't get them? Not sure where you live, but I could ask around to dig some up for you. The ones I know are in North America, but there's probably someone in Europe that carries them.

No problem getting them in europe

any eti projecst are always welcome.

while investigating the links arph posted, i found this:

(http://www.eskimo.plus.com/fxstuff/slacktrem.png)

i DO have some '69's, so will try it and report back.

got my vactrol today, so i guess i should get to work on a veroboard for the cardinal. ;)

thanks guys!!

Here is what I have in mind:

Hope its readable..

(https://dl.dropbox.com/u/1849818/published_images/IMAG0627.jpg)

Not sure it'll work as drawn.

http://www.diystompboxes.com/smfforum/index.php?topic=101884.0

Josh @ 1776 spotted two typos in my version of the schematic, which have been corrected. They were also correct in the layouts:
C12, the hold cap for the LFO in the IC version, was shown as 1uF in the schematic. It's 10uF (the same value commonly used for that purpose).
C7, the treble cut cap on the "full-range" side, is 2.2nF, not 22nF as the schematic originally showed. (Big difference!)

~arph, please note that the second change affects your schematic, and sorry for the errors in orders of magnitude.  :icon_redface:

I will most likely replace my schematic with Josh's at some point; his looks much better than mine. I'm still getting used to Eagle and just using reference points instead of running wire all over the place.

jimi, I'll get onto translating that eti circuit to this century. it is interesting because it ties all the supply pins to ground on the 4049, and turns the inverters on with the output signal, which makes for a rather non-linear response.

mdway, in my case 0 job = 0 $$$ = 0 new parts, local store or internet.

cool, thanks bro!

Quote from: midwayfair on March 10, 2013, 11:56:05 PM
These layouts are verified 3/10/13. All schematics have been updated (there were a couple nets run incorrectly, and I adjusted the values on the bias modulated LFO to keep it from crapping out at high speeds.)

Apologies for the handful of small parts, but I really didn't want to have to add another row. Though to be perfectly honest, I can't imagine how many people besides me really torture themselves with complicated circuits on perfboard. There will be a PCB project of this, but I'll wait until that's finalized to announce it.

Perfboard layout for the IC version:
(https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Nonmini%20builds/Cardinal%20Tremolo%20-%20IC%20LFO%20version.png)
PDF: https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Nonmini%20builds/Cardinal%20tremolo%20-%20IC%20LFO%20version.pdf

Bias modulated version in a 1590A layout:
(https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Cardinal%20Tremolo%20-%20bias%20modulated%20%28transistors%29.png)
PDF: https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/cardinal%20tremolo%20-%20bias%20mod%20version.pdf

]


jon, pardon my stupidity...

but looking at this thing, i'm confused...

i see led/ldr combos on the layout twice..
is that what you used, or do i have to buy another vactrol (i only ordered one)

:( It's two vactrols, Jimi. I thought I cleared that up a few pages back and in the description.

I'll mail you a VTL5C1 in the name of the cause. Just PM me your address and I'll get it out to you tomorrow.

awww, that'd be awesome, jon, thanks so much!!!

pm sent!

~arph,

I breadboarded as per your mosfet cardinal, but it "didn't work". there was no sign of any output below 200 Hz, and not much at 200Hz either. is there a 10M missing from pin 6 to ground?

Yes, there is one missing there. Nice to hear someone tried it. I'm not too surprised it doesn't work, as I just drew it out of my head and I have no experience with the CD4007 at all. :P
You can use an audio probe to see if the problem is with the mosfets as resistors. or earlier in the chain.
Btw, you need a 1M to pin 3 as well and then tailor the output of the LFO for optimal response.

hmmmm, I seem to recall I had 470k there anyway. I'm not sure where the signal goes, but it certainly does go. not really knowing what I'm doing doesn't help, and I had the switch on the 2n2/470pF wired wrong.

I'll have to try it again, I s'pose.

jon, the vactrol came in today, thanks so much bro!!

look forward to getting started on it soon. ;)

I have a question about the 2n2 cap. at 22nF, the filter f was 723Hz, but with the corrected 2n2, it now goes to 7230Hz, yes? I mean, I know the answer is yes, but I'm just checking the values.

I had another read and redraw, so I understand the circuit somewhat better. ~arph, the mosfets just didn't seem to like doing things w/ resistors between them and supplies. I re-breaded the circuit with jfets, and there was lots of bass missing due to the source cap being too low. but the fets would chew just about all the signal thereafter, anyway.

Quote from: duck_arse on March 25, 2013, 09:03:13 AM
I have a question about the 2n2 cap. at 22nF, the filter f was 723Hz, but with the corrected 2n2, it now goes to 7230Hz, yes? I mean, I know the answer is yes, but I'm just checking the values.

I had another read and redraw, so I understand the circuit somewhat better. ~arph, the mosfets just didn't seem to like doing things w/ resistors between them and supplies. I re-breaded the circuit with jfets, and there was lots of bass missing due to the source cap being too low. but the fets would chew just about all the signal thereafter, anyway.

Yes, I'll fix the numbers in the write-up. Pretty dumb that I knew it was a 2.2nF on the breadboard but still punched in 22nF on the calculator when doing the write-up ... I think 723 just looked in writing like a more reasonable number. I know a single-order filter isn't exactly the steepest rolloff, but 7K is some really high notes to still accurately produce the effect. :/

Incidentally, I tried it with discrete MOSFETs over the weekend -- I DID get it to trem in both positions by feeding foltage into the gate (you need a decoupling cap between the LFO output and the MOSFET gate if you didn't already use one -- though I couldn't tell you the electronic reason it needs to be there), but they sounded distorted and just terrible. I think I got FETs to work this way, too; same thing with the distortion.

I tried a pot from V+ to ground on the mosfets, just to see, and on the cro, they made huge distortion on the neg half-cycles before they cut off.

jon,

I've got a modified-to-jfet cardinal working on my breadboard, but I'm not telling anyone until I've heard what it's supposed to sound like. I can see nothing but a white space in place of your sneak preview video; is this really here and I'm gone blind?

I thought 59 redraws of yr circuit would have coverd all possible ways to connect 4 resistors and a cap to a fet. after 135 rebuilds, I decided I'd give it one more day on sunday, and it seemed the idea was to leave out the cap and 1 r. it was working, sans distortion! hurray.

it's now monday, more redraws and rebuilds, the parts are back in, and now working, w/added sound! what sound, and the balancing of the fets to follow .....

Quote from: duck_arse on April 08, 2013, 10:44:52 AM
I've got a modified-to-jfet cardinal working on my breadboard, but I'm not telling anyone until I've heard what it's supposed to sound like. I can see nothing but a white space in place of your sneak preview video; is this really here and I'm gone blind?

Woops. I can't go back and edit the first post, but this is the "full version" demo:



Can't believe I forgot to post it in this thread! :P

I hid the sneak peak video because it wasn't the final version of the circuit. :)

glad to hear you got it working with FETs! I'm excited to hear it.

i haven't even had a chance to consider laying this out yet... sucks. too much stuff i gotta do...i hate when life interferes with my addiction!! ;)

hmmm, so it's supposed to sound like an auto-wah connected to a double speed osc, with bass tremolo. well, that is good news, cause that's sort of what I'm getting. and super bright and hard on the bridge pickup.

with the pso, I can get sine all the way to that yang-yang-yang type square wave sound, but I'm going to need to try and balance the waveforms for overlap with seperate fet biases.

we'll see.

Quote from: duck_arse on April 08, 2013, 11:57:08 AM
hmmm, so it's supposed to sound like an auto-wah connected to a double speed osc, with bass tremolo. well, that is good news, cause that's sort of what I'm getting. and super bright and hard on the bridge pickup.

with the pso, I can get sine all the way to that yang-yang-yang type square wave sound, but I'm going to need to try and balance the waveforms for overlap with seperate fet biases.

we'll see.

There are a couple ways to adjust the overall treble content:

1) A simple gate > drain treble bypass cap (100-220pF) on the input stage to soften things a little.
2) A 1nF or so cap across the volume pot.
3) You could shift the treble cutoff downward some by adjusting the input cap to the treble stage and the treble cut cap at the input of the full-range stage. This will start to move toward phaser sounds, though. The harmonic tremolo on the amps was actually quite bright sounding every other cycle.

However, I caution against doing this. The pedal sounds different in isolation than in a band mix. Here's what someone told me after testing out the pedal in the video, after we had some discussion regarding the overall brightness of the effect:

QuoteThe bypass vs activated was also much less noticeable in a band setting.  Especially with a little dirt in front of it.  The increased treble actually made the effect a little more noticeable and it "cut" nicely through the mix.  I guess the question is whether others would find it to much.  I use more treble than most to begin with.  It may lose some of it's "sparkle" if it's changed.  Sorry, lacking a better term than "sparkle".

That sounds killer.  The last thing I need is one more thing to build, but I'm sure happy it's this one.  Well done.

jon,

I watched most yr vid before the connection got hung-up. I even thought I recognised part of what you were playing. don't ask me what it was, though.

I've currently got 1nF to the treble instead of 470pF, I just haven't reached up for it yet. I don't have a vol, just mix resistors. I'm hoping to rework the fets for a bit of headroom, and near unity overall. I've got 2 cases waiting for the "world's best tremolo" I was designing to death 10 years ago. they are ready for 3 pots and 2 rocker switches, which looks a good fit.

except for the third pot hole, cause now I've got a bias pot for the treble side: the different (treble trem) waveform/threshold? verses depth setting has some quite interesting. and then I put a perkolator in front of it, and it became *VERY* interesting indeed.

but what do I know?

jon, I just read yr troubles w/ counterfeit j201's on that thread. did any value changes come out of your findings? I ended up selecting mine, w/ 3 diferent part #'s for the amplifying fets.

Quote from: duck_arse on May 01, 2013, 11:31:54 AM
jon, I just read yr troubles w/ counterfeit j201's on that thread. did any value changes come out of your findings? I ended up selecting mine, w/ 3 diferent part #'s for the amplifying fets.

It wasn't so bad. I didn't change any parts, but we're going to suggest socketting the drain resistors to get to the following voltages:
Target bias voltages (acceptable range): Q1: ~8v (6v-8.5v); Q2: ~7v (5v-7.5v); Q3: 3.5v (2v-4.5v).

We did have a handful of Tayda J201s that were biasing all the way down below 2v in Q3, which was just nuts (they're very loud at 2v, but quickly drop off and get distorted below that, obviously). I did find that Tayda's 2n5457s can be plugged in no problem, though. They're a little gained up in Q1 and Q2, but I didn't have any distortion issues with single coils or minibuckers. I got other fets to work with different drain resistors, including 2SK30 (twisted the leads), and almost anything will work in Q1 and Q2*. The weird thing is this is the opposite of what happened on the breadboard, so I wonder if maybe I was using a different drain resistor at the time. Usually if 2N5457 is an option, that's what I'll use. I love the sound of them.

I don't have any known-to-be-genuine Fairchild 2N5457s to test.

*I may have been too greedy on Q3. I could have gone with a tiny source resistor and a 47uF or 100uF cap and that would have made pretty much every FET useable, but grounding the source maxed out the gain/output and saved two parts.

how odd, my first drawing of yr circuit has only 3 voltages marked on it, all j201's right in the ranges you gave. after much fartarsing about, I ended up with mpf106 as q1, j210 as q2 and j201 as q3. I reduced the q2 and q3 drains to 3k3 and split the q2 source to 470R +470R//10uF. I still need to listen again and stuff about w/ mixing resistors at the output.

my j201's are all natsemi, bought around 2001. the 2n5457's I've had for 25 or more years, also natsemi, so not much counterfeit worries there. about time I used them for something.

Awesome project! I think I'll work up a PCB with the TAPLFO and see how it goes! Is the schematic on the first page/first post still correct? You had also mentioned that there was a compromise for C8 - 2.2n for one mode and 470p for the other. Would it be beneficial to make the mode switch a 3PDT switch and switch that cap? I guess it would be hard to find a three position 3PDT though.

EDIT: Actually not that hard http://www.amazon.com/3PDT-Mini-Toggle-Switch-Center/dp/B001TJ6MDK

Yes, if you want to spend extra for the 3pdt switch, knock yourself out. I have an eagle layout for the TAPLFO version if you want it. It's mostly confirmed; I've made a correction since my build, bout it should be fine. I was planning on uploading it to pedal geeks united, but I haven't gotten around to it.

I had never heard of Pedal Geeks United until now! Thanks for mentioning it, I'm going to have to check it out. As far as the taplfo version, I've worked with electric druid's lfo a few times before, so I've got that part down, I just wanted to make sure the schematic on the first page was still the most up to date. I noticed you mentioned some updates throughout the thread, but I'm not sure if that first schematic reflects them or not. Thanks!

Quote from: mth5044 on May 08, 2013, 01:27:27 PM
I had never heard of Pedal Geeks United until now! Thanks for mentioning it, I'm going to have to check it out. As far as the taplfo version, I've worked with electric druid's lfo a few times before, so I've got that part down, I just wanted to make sure the schematic on the first page was still the most up to date. I noticed you mentioned some updates throughout the thread, but I'm not sure if that first schematic reflects them or not. Thanks!

The schematic on the first page is currently "my" schematic for the basic project. The forthcoming PCB project has one or two small changes, but nothing substantial. When I get home tonight, I can try to remember to send you the Eagle files for the TAPLFO version, if you want to save yourself the trouble of drawing the schematic. There's a couple weird, specific things that needed to be done with it compared to Taylor's TTT, because you have to drive two LEDs. I'll tell you that one of them is the transistor after the LFO output pin is backwards ...

Interesting! Sure I'd love to see your schematic, I'll PM my email.

Cardinal with Tap Tempo LFO?  I'd be very curious to see this too. I'd already abandoned the idea of buying a tremolo over building this or a Blue Warbler :icon_lol:

Is it o.k to send you my email?

Quote from: Jazznoise on May 08, 2013, 07:27:38 PM
Cardinal with Tap Tempo LFO?  I'd be very curious to see this too. I'd already abandoned the idea of buying a tremolo over building this or a Blue Warbler :icon_lol:

Is it o.k to send you my email?

I'll just post it here, as soon as I have time to actually turn my home computer on ...

(https://dl.dropboxusercontent.com/u/9878279/Jon%20Patton%27s%20layouts/Cardinal%20Tremolo/Tap%20Tempo%20Cardinal.png)

The Eagle .brd file is on Pedal Geeks United.

Despite some funny looking stuff (yes, Q4 really is collector to ground -- it worked better that way), this is verified. R16 and R17 may actually need to be socketted -- I ended up with 22K for R16. I had one heck of a time with the LEDs: Two superbrights is pretty much the absolute max the chip can drive, so I had to find some other way of referencing the LED. Turned out to be simply a matter of sending it to ground. R18 is to make sure it stays in sync with the vactrols. Incidentally, if anyone's interested in making a tap tempo univibe type thing, that right there is an easy way to get the oscillation of one vactrol out of sync with another to create a loping effect.

It does tick in triangle and "ramp up" wave settings in Harmonic mode above 12:00 on the depth, which seems unavoidable. But to be honest, settings like that have basically no harmonic effect anyway because there's no frequency crossover, and there's no noticeable ticking in the same settings when in full-range mode. The sine wave and "humps" setting are exceptional in Harmonic mode, and all the full-range stuff from the TTT is there in good working order (including all the glitch settings). There's a ton of depth. Most of the time I'm not above noon.

I built one on the last round of prototyping boards, before I made one or two fixes ...
(http://jonpattonmusic.files.wordpress.com/2013/04/cardinal-tap-tempo.jpg?w=300)(http://jonpattonmusic.files.wordpress.com/2013/04/cardinal-tap-tempo-guts.jpg?w=300&h=175)

Looks great.
Do you get any ticking with the non-TAPFLO version?
I was about to build this and decided I should try an op-amp work-a-like first (I seem to be shying away from discrete transistors these days). However, I am not sure I'm having fun anymore. It works beautifully, but I can hear the LFO in the audio pathd depsite quite brutal power filtering. It is probably the dodgy grounding you get on a breadboard, but I am not sure I want to pull the trigger and build it lest it continues to tick/whine.
Also, have you found that are there any LFO waveshapes that are particulalry good or bad for harmonic tremolo?

Quote from: samhay on May 10, 2013, 08:30:40 AMDo you get any ticking with the non-TAPFLO version?

I get some line noise with single coils, which modulates, so there's some swooshing (it's not really noticeable in a mix or while playing), but no ticking.

Quote from: samhay on May 10, 2013, 08:30:40 AMI was about to build this and decided I should try an op-amp work-a-like first (I seem to be shying away from discrete transistors these days). However, I am not sure I'm having fun anymore. It works beautifully, but I can hear the LFO in the audio pathd depsite quite brutal power filtering. It is probably the dodgy grounding you get on a breadboard, but I am not sure I want to pull the trigger and build it lest it continues to tick/whine.

Okay, the WHINE you're getting is something different. I used FETs because the treble side had a high pitched whine that was noticeable when using transistors BJTs. I also had some whine in the tap tempo version, but that was related to the TAPLFO chip, and it got filtered out with the right sized resistors on Q4. If it's the same thing in yours, it can be filtered out in the audio path. You should be able to get rid of it with a PF cap in the feedback loop of the treble side, counterintuitive as that may be. Keep it really small, though - 10pF is probably enough. If that filters out too much, you can also put it across the volume pot or something. You could also try some series resistance in front of the output volume control, to get an output impedance closer to a FET's. Like just a 1K or something.

For the ticking, I want make sure it's actual ticking and not just WOOSH sounds happening very quickly. If I knew more about how you've done the tremolo on both sides, I might have other suggestions -- but there are some ways of producing tremolo on an IC that would be modulating bias and that, when it happens very quickly, could sound like ticking. If it's just the general LED wup wup wup (yeah, I'm full of really specific sounds, eh?), then yeah, it's probably the grounding. If you do an etch of your version, be sure to separate the ground planes or just avoid a ground plane altogether.

Quote from: samhay on May 10, 2013, 08:30:40 AMAlso, have you found that are there any LFO waveshapes that are particulalry good or bad for harmonic tremolo?

The harmonic phasy effect occurs when the frequencies cross over between the treble and full-range sides. Unlike in a phase 45, there's no "permanent" dry signal here, so you're relying on the two sides to have a point where they are of similar amplitude. (This, incidentally, is why you hear more "gloop" when bass and treble strings are played together, rather than just in a midrange note by itself.) This can't happen with a really hard waveform, like a true square wave, because there just won't be any point where the frequencies line up.

But wait a minute, you say. The output of the LFO I used is a triangle, and that's a pretty hard waveform. And you're absolutely right. In fact, I have seen the scope images to prove it. But the vactrols have a sluggish response, and this makes the triangle come out sounding more like a sine wave.

Quote from: midwayfair on May 10, 2013, 09:48:42 AM
But wait a minute, you say. The output of the LFO I used is a triangle, and that's a pretty hard waveform. And you're absolutely right. In fact, I have seen the scope images to prove it. But the vactrols have a sluggish response, and this makes the triangle come out sounding more like a sine wave.

could this be due to human logarithmic perception vs linear reality? (genuinely curiosity driven question badly phrased so as to appear rude - this is not intentional, i'm tired)

Quote from: artifus on May 10, 2013, 09:53:40 AM

Quote from: midwayfair on May 10, 2013, 09:48:42 AM
But wait a minute, you say. The output of the LFO I used is a triangle, and that's a pretty hard waveform. And you're absolutely right. In fact, I have seen the scope images to prove it. But the vactrols have a sluggish response, and this makes the triangle come out sounding more like a sine wave.

could this be due to human logarithmic perception vs linear reality? (genuinely curiosity driven question badly phrased so as to appear rude - this is not intentional, i'm tired)

It absolutely could be. And this doesn't sound rude at all to me. I mean, falible human ears are why pitch vibrato happens in a Magnatone amp, for instance, even though that's just another example of phase cancellation. Similar physical phenomena producing completely different effects.

Quote from: midwayfair on May 10, 2013, 09:56:30 AM

Quote from: artifus on May 10, 2013, 09:53:40 AM

Quote from: midwayfair on May 10, 2013, 09:48:42 AM
But wait a minute, you say. The output of the LFO I used is a triangle, and that's a pretty hard waveform. And you're absolutely right. In fact, I have seen the scope images to prove it. But the vactrols have a sluggish response, and this makes the triangle come out sounding more like a sine wave.

could this be due to human logarithmic perception vs linear reality? (genuinely curiosity driven question badly phrased so as to appear rude - this is not intentional, i'm tired)

It absolutely could be. And this doesn't sound rude at all to me. I mean, falible human ears are why pitch vibrato happens in a Magnatone amp, for instance, even though that's just another example of phase cancellation. Similar physical phenomena producing completely different effects.

I suspect it has a lot more to do with the blessfully slow response of both the LED and LDR, which smooths out any sharp bits in the LFO.

Jon - Thanks for the suggestions. I guess the noise might be similar to yours - it's not ticking, but rather moaning/swooshing/whining; I don't really know how to describe it either. i think it is probably the current through the LEDs causing ground weirdess, but need to get the scope out.
The audio side of the tremolo I currently have on the breadboard is very different to yours. The only real similarities are the LFO, a vactrol and the end effect. It was inspired by the same comments that Jimi made to you, but got off the ground when I started thinking about a dual band compressor - so I have you, Jimi and Merlin B to thank for the impetus. I will post it once I have convinced myself it is worth sharing, and will try not to derail your thread in the meantime.

Quote from: samhay on May 10, 2013, 12:11:20 PM
I suspect it has a lot more to do with the blessfully slow response of both the LED and LDR, which smooths out any sharp bits in the LFO.

and how did you, as a human being, perceive that phenomena?

i had recently been reading about pwm, led brightness, lfo's and human perception/cognition. hence my question. it is an interesting subject. also look up: psychoacoustics. my! it's a big universe!  :P

Quote from: samhay on May 10, 2013, 12:11:20 PMwhen I started thinking about a dual band compressor

If you keep posting phrases like this, derail away ... I tried getting one of those to work recently and the results weren't exactly pretty. Really want to see what you came up with.

I'm intrigued by how much design space there is in simple signal split mechanisms, stuff that goes way beyond a harmonic tremolo or stereo splitting. Like someone 's recent request for an effect that oscillated between a clean and dirty signal.

Quote from: artifus on May 10, 2013, 12:18:02 PM

Quote from: samhay on May 10, 2013, 12:11:20 PM
I suspect it has a lot more to do with the blessfully slow response of both the LED and LDR, which smooths out any sharp bits in the LFO.

and how did you, as a human being, perceive that phenomena?

i had recently been reading about pwm, led brightness, lfo's and human perception/cognition. hence my question. it is an interesting subject. also look up: psychoacoustics. my! it's a big universe!  :P

No doubt. PWM works with LEDs, at least in part, because our eyes have a pretty poor time resolution and we use on-the-fly averaging. One big question is to what extent we are digital (use quantum mechanics), which is what I do for a day job.

Quote from: midwayfair on May 10, 2013, 12:30:02 PM

Quote from: samhay on May 10, 2013, 12:11:20 PMwhen I started thinking about a dual band compressor

If you keep posting phrases like this, derail away ... I tried getting one of those to work recently and the results weren't exactly pretty. Really want to see what you came up with.

I'm intrigued by how much design space there is in simple signal split mechanisms, stuff that goes way beyond a harmonic tremolo or stereo splitting. Like someone 's recent request for an effect that oscillated between a clean and dirty signal.

Yeah, the circuitry certainly mounts up pretty fast. Once I have the tremolo off the breadboard (or buy another breadboard), I will try the compressor out. I am pretty sure I now know how to do it, but have to work out a few kinks.

Quote from: artifus on May 10, 2013, 12:18:02 PM

Quote from: samhay on May 10, 2013, 12:11:20 PM
I suspect it has a lot more to do with the blessfully slow response of both the LED and LDR, which smooths out any sharp bits in the LFO.

and how did you, as a human being, perceive that phenomena?

i had recently been reading about pwm, led brightness, lfo's and human perception/cognition. hence my question. it is an interesting subject. also look up: psychoacoustics. my! it's a big universe!  :P

We hear sound in a logarithmic way, so actually a triangle wave sounds kind of exagerated to is. The smoothness of a triangle in an vactrol controlled scenario is really due to their poor response to chance. The higher order harmonics are really what dictate how abrupt the rate of change is.

Thanks for posting that schem, MWF! You didn't happen to try filtering the LFO to prevent the ticking? I'll have to dig around for our PIC Coder.

In response to the multiband thing, it's a peculiar type of processing that is often very context reliant. Things like Vocoders would be a classic example. Any type of filtering requires energy in desired bands. Multi band compression is messy and even things such as makeup gain can be a total pain - I rarely used it when mixing, something would have to be pretty broken to require that solution.

hoping to finally be able to start on this this week jon... really looking forward to it!!
just so i'm clear, what is the easiest/best version you've come up with?
remember, homie here is a hack. ;)

Quote from: pinkjimiphoton on May 11, 2013, 11:34:37 PM
hoping to finally be able to start on this this week jon... really looking forward to it!!
just so i'm clear, what is the easiest/best version you've come up with?
remember, homie here is a hack. ;)

The one on page 1 is correct, except that C14 is redundant with C13.

thanks jon, gonna start working up a vero tonite hopefully..

dear god, the addiction is kicking in again... ;)

Hi Jon,

First of all I would like to say Brovo as I think your trem sounds amazing. I had completely lost interrest in tremoloes since i sold my big box Pulsar but this one sounds really interresting and much more useful, musically.

I have a question about your demo on this clip:

http://www.youtube.com/watch?feature=player_embedded&v=SyFoTRWPq_A

It's not clear to me which LFO you are using in this one.
It sounds really deep and a lot better than your first demo.

Quote from: drolo on May 30, 2013, 06:31:58 AMI have a question about your demo on this clip:

http://www.youtube.com/watch?feature=player_embedded&v=SyFoTRWPq_A

It's not clear to me which LFO you are using in this one.
It sounds really deep and a lot better than your first demo.

That demo is with the TL072 IC-based LFO, the one shown in the schematic on the first page.

I know most folks on DIYSB are all about etching and vero and such, but I just thought I'd stick a note here that 1776 Effects released the PCB project for this today: http://1776effects.com/store/

It's red and has a bird. <3

I've been eagerly waiting this.  Just ordered..Thanks

Thanks for this article Midwayfair!
It will take some time to read through all the pages but I'm certainly going to try this one,.
I'm also interested in that 11 FET version you mentioned in the video.

This article inspired me to experiment with my uni-vibe based tremolo and I got some really interesting sounds out of it.
If there's any interest I can post it in a different tread as not to derail this one.

Quote from: Liquitone on June 09, 2013, 11:34:42 AM

This article inspired me to experiment with my uni-vibe based tremolo and I got some really interesting sounds out of it.
If there's any interest I can post it in a different tread as not to derail this one.

I would definitely like to have a look at that :-)

Quote from: midwayfair on June 07, 2013, 11:07:51 AM
I know most folks on DIYSB are all about etching and vero and such, but I just thought I'd stick a note here that 1776 Effects released the PCB project for this today: http://1776effects.com/store/

Any plans to publish the PCB for the TAPLFO version?

Quote from: drolo on June 11, 2013, 02:03:26 PM

Quote from: midwayfair on June 07, 2013, 11:07:51 AM
I know most folks on DIYSB are all about etching and vero and such, but I just thought I'd stick a note here that 1776 Effects released the PCB project for this today: http://1776effects.com/store/

Any plans to publish the PCB for the TAPLFO version?

As noted above, the Eagle files are on Pedal Geeks United. I won't be printing a run in part because it would compete with Josh's (1776's) PCB run of the standard circuit and partly because it's such an expensive board to populate, but if someone else wants to make themselves a couple from OSH Park, they're welcome to do so with impunity as long as it's not a commercial endeavor.

Quote from: midwayfair on June 11, 2013, 02:09:58 PM

Quote from: drolo on June 11, 2013, 02:03:26 PM

Quote from: midwayfair on June 07, 2013, 11:07:51 AM
I know most folks on DIYSB are all about etching and vero and such, but I just thought I'd stick a note here that 1776 Effects released the PCB project for this today: http://1776effects.com/store/

Any plans to publish the PCB for the TAPLFO version?

As noted above, the Eagle files are on Pedal Geeks United. I won't be printing a run in part because it would compete with Josh's (1776's) PCB run of the standard circuit and partly because it's such an expensive board to populate, but if someone else wants to make themselves a couple from OSH Park, they're welcome to do so with impunity as long as it's not a commercial endeavor.

Thanks Jon, that's great :-)

Jon, I am trying to cook something up inspired by your circuit and was having a look at the low pass frequency you use to have something to start with. You mention your lowpass cuts at 723Hz, but with the 10k and 2n2 in your schematic, I get the result 7.23kHz. Is that maybe a typo? (22n would normally result in 723 Hz) Or maybe I am calcuating this wrong ... Sorry if I am missing some obvious detail

drolo, I had the same question, lost in the thread noise ......

http://www.diystompboxes.com/smfforum/index.php?topic=101722.msg902991#msg902991

Quote from: duck_arse on July 06, 2013, 08:05:37 AM
drolo, I had the same question, lost in the thread noise ......

http://www.diystompboxes.com/smfforum/index.php?topic=101722.msg902991#msg902991

oh I had missed that .. thanks  :-)

A couple of quick questions about the wave and volume pots.  For external pots, what taper is best - I assume audio for volume but not sure about wave?  Do wave adjustments affect the volume?  I think I can live without a volume control, but I'm not sure if having the external wave pot will allow me to make adjustments that will end up needing a volume correction.

Quote from: GGBB on November 06, 2013, 08:11:17 AM
A couple of quick questions about the wave and volume pots.  For external pots, what taper is best - I assume audio for volume but not sure about wave?  Do wave adjustments affect the volume?  I think I can live without a volume control, but I'm not sure if having the external wave pot will allow me to make adjustments that will end up needing a volume correction.

Linear for both pots.

The volume isn't really necessary, but there's a bunch of boost available if you want to use it as a preamp. The wave pot is really nice if you want the mode switch.

Quote from: midwayfair on November 06, 2013, 10:53:17 AM
Linear for both pots.

The volume isn't really necessary, but there's a bunch of boost available if you want to use it as a preamp. The wave pot is really nice if you want the mode switch.

Thanks Jon.  I am itching to build this (my 10th Ann. prize) as soon as I get some free time.  I absolutely love the demos I've heard.

I believe you did a tap-tempo version of this right?  Can that be done using the 1776 PCB along with a second board?

EDIT:  Never mind - found the answer on your original schematic.  Awesome!

This is the Univibe mod! Very exciting.

THEORETICAL

So, Dane Kinser (eldanko) over on Madbean accidentally discovered that you can make the Cardinal sound like a vibe by replacing C6 with a much bigger cap, in his case 33nF. This got me thinking whether we could use a single toggle to replace the center mode with the vibe mode.

It requires a DPDT on/on/on.

It's wired thusly:
DPDT on/on/on
1 4
2 5
3 6

-Jumper 1 and 5.

-Replace R6 on the PCB with a much larger value, e.g. 33nF.

2: This is the ground connection (pad 2).

3: This connects to the pad on the PCB that goes to C6 (pad 1)

4: This connects to the pad on the PCB that connects to the gate of Q3 (pad 3)

-Solder a smaller value cap across lugs 3 and 6. (See below for values and cutoff frequencies.) We will call this the "switched" cap.

The modes will now be:

Up/right - Normal tremolo
Center - Harmonic
Down/left - Vibe

How this works:

In the center, C6 + switched cap create series capacitance.

When the switch is up/right, the emiter of Q3 is connected to lug 5, which is jumpered (internally) to lug 1, which is now connected to the ground connection.

When the switch is down/left, C6 is connected to ground, and the cap across lugs 3&6 are disconnected.

Switched + C6 cap values and calculations:

-2.7nF + 33nF will equal ~2.5 nanofarads. Cutoff frequency will be 6366. This isn't that close to the original 7234, but remember that we're dealing with harmonics and it's better to go a little lower rather than higher with the cutoff.
-3.9nF + 33nF will equal ~3.5 nanofarrads. Cutoff frequency will be 4547 (not too far from Dane's 4822 with a 3.3nF)

R5 could be (VERY) mildly adjusted as well if you want to hit a particular cutoff frequency. For instance, if you want to get even closer to the cutoff frequency of the stock values, you can use a 9.1K with 33nF and 2.7nF caps to get a cutoff of 6995. Or to get really really close to Dane's original cutoff, you can use an 8.2 with 33nF and 4.7nF caps.

It would be best to experiment with the larger value cap in C6 first to get the vibe sound you want and then calculate the switched cap based on that.

I will give this a go in one of my builds, maybe in the tap tempo version since I need to open it up to add Josh's optical bypass to it.

Thanks to everyone in the switch thread that showed me the DPDT on/on/ons (armdnrdy, GGBB, slacker).

This is awesome Jon!  But I just built mine over the weekend - doh! 

Quote from: midwayfair on November 25, 2013, 03:22:37 PM
It requires a DPDT on/on/on. Croquet hoop noted that there may be two types of DPDT on/on/on switches. You need the kind with an internal jumper across lugs 1 and 5. This is apparently most of them, but be sure to check.

Can you clarify that?  I've never run across any that were like that.  Are you going by the diagram I pointed to in the other thread?  There, the 1-5 connection is drawn in red and is meant to be added to the switch, not an internal connection.  Please clarify.

Quote from: GGBB on November 25, 2013, 03:38:45 PM
This is awesome Jon!  But I just built mine over the weekend - doh!  

Quote from: midwayfair on November 25, 2013, 03:22:37 PM
It requires a DPDT on/on/on. Croquet hoop noted that there may be two types of DPDT on/on/on switches. You need the kind with an internal jumper across lugs 1 and 5. This is apparently most of them, but be sure to check.

Can you clarify that?  I've never run across any that were like that.  Are you going by the diagram I pointed to in the other thread?  There, the 1-5 connection is drawn in red and is meant to be added to the switch, not an internal connection.  Please clarify.

Oh, I thought it was internal. I'll fix that.

EDIT: If you already built yours, this shouldn't require redrilling or anything. :)

Finally got around to firing this up and all I can say is wow!  Jon - this is a beautiful pedal - thanks for contributing this.  Now I want to build a tap tempo version.

Some notes from my build:

If you are using the 1776 Effects PCB, pay attention when installing the vactrols.  On the LED side, the anode is the square pad, not the other way around like one would expect.  This means that VTL5C1s will be installed label side down.  She don't make no nicey sounds if you get that wrong like I did at first. 

The vibe mod is really really nice.  I went with a 22n cap for C6 with a 2n7 on the switch.  I could have been equally as happy with a 33n for vibe mode (although if forced to choose I would have picked the 22n), but liked the 22n-2n7 combination a little better than the 33n-2n7 combination for harmonic mode, and actually preferred that to the stock 2n2 alone for harmonic.

I've decided to go with an external volume control as I found that in normal tremolo mode you can have so much depth that you need to bring the volume up to compensate.  The wave control can make this even more necessary.  It should be said that this is a pretty awesome sounding normal tremolo in addition to harmonic and vibe.

Everyone should have one of these.

Wow, thanks GGBB! Glad you like it, and thanks so much for verifying the Vibe mod. :)

Quote from: midwayfair on June 07, 2013, 11:07:51 AM
I know most folks on DIYSB are all about etching and vero and such, but I just thought I'd stick a note here that 1776 Effects released the PCB project for this today: http://1776effects.com/store/

It's red and has a bird. <3

freekin' sweet, just ordered one. this looks like it woulda been a beetch to vero!!
can't wait to finally build this thing!!
thanks jon!!

Quote from: midwayfair on December 21, 2013, 10:11:58 PM
Wow, thanks GGBB! Glad you like it, and thanks so much for verifying the Vibe mod. :)

I should also add that I tried going bigger for the vibe mode - 68n and 100n (out of 47n at the moment).  But it's too far in the other direction and loses the effect.  22n or 33n seems to be the ticket.  And when you're in vibe mode, the wave control comes in really handy.  There's a really interesting interaction between the depth and wave controls in both harmonic and vibe modes - you can find a lot of different subtleties in there.

Quote from: GGBB on December 21, 2013, 10:38:59 PMThere's a really interesting interaction between the depth and wave controls in both harmonic and vibe modes - you can find a lot of different subtleties in there.

I would expect the triangle wave to have a tiny bit of the univibe's lope.

I'll get to hear it soon enough ... I'm putting the mod in a stereo tap tempo tremolo I'm making "because I could".

I bet the stereo version is doooopeeee. Did you just invert the LFO? Can the TAPLFO supply enough current for 4 LEDs?

EDIT: wait nevermind I just remembered the TAPLFO drives a transistor.. you can have as many LED's as the heart desires (and can run on 9V)

Quote from: mth5044 on December 21, 2013, 11:23:40 PM
I bet the stereo version is doooopeeee. Did you just invert the LFO? Can the TAPLFO supply enough current for 4 LEDs?

Some nice folks informed me that I just needed a PNP and set it up like the NPN. It actually has depth to spare -- the regular version worked fine with three LEDs after some work, and this one just has two LEDs per transistor, and they don't interfere with each other.

To be honest, I have no way to hear how it actually "sounds." It's slightly different from the Cardinal. All I did was confirm that both channels would work and then wrack my brain for days figuring out the switching and all the mods he wanted and making like three layouts.

I like a challenge, it's really the only reason I took the order. I probably wouldn't make another one and I was just shocked he was willing to pay the asking price.

That's interesting! So another signal is tap'd off pin 5 of the chip along with a 10k to the base of a PNP with it's emitter grounded and a collector to the LED's?

Quote from: mth5044 on December 21, 2013, 11:54:36 PM
That's interesting! So another signal is tap'd off pin 5 of the chip along with a 10k to the base of a PNP with it's emitter grounded and a collector to the LED's?

Yes, except I found that the PNP had to be in backwards (emitter to LEDs, collector grounded). I guess that makes sense -- it's an NPN circuit.

Cool! Thanks Mr. P!

Sorry, one more thing -

Quote from: midwayfair on November 25, 2013, 03:22:37 PM
It's wired thusly:
DPDT on/on/on
1 4
2 5
3 6

-Jumper 1 and 5.

-Replace R6 on the PCB with a much larger value, e.g. 33nF.

2: This is the ground connection (pad 2).

3: This connects to the pad on the PCB that goes to C6 (pad 1)

4: This connects to the pad on the PCB that connects to the gate of Q3 (pad 3)

-Solder a smaller value cap across lugs 3 and 6. (See below for values and cutoff frequencies.) We will call this the "switched" cap.

Just to make sure, you say R6, but that was probably a little slip up and should be C6. But what I am a bit confused about is the wiring of lugs 3 and 4. For lug three, isn't pad 1 the pad that goes to C7, not C6? If not, then isn't pad 3, the pad that connects to the gate of Q3, the same pad that connects to C6?

And finally, in the taplfo schematic you have, you have the 3904 collector going to ground, but in the taplfo datasheet with the tap trem, the collector is grounded. Perhaps it doesn't matter, but in this case, as long as the NPN and PNP transistors have opposite connections per your last comment it may be ok? I end everything in a question mark because I don't actually know anything?

@ jon - what type # is your pnp that needs backwarding? just out of interest, mind.

Quote from: duck_arse on December 22, 2013, 08:31:24 AM
@ jon - what type # is your pnp that needs backwarding? just out of interest, mind.

2n3906. Definitely 100% better when backwards.

@mth5044: I'm going by the 1776 build doc schematic, since that's the one most people use. That post was a x-post from the Madbean forum (which is also the 1776 home base). I just haven't redrawn my schematic to match Josh's numbering.

Quote from: midwayfair on June 07, 2013, 11:07:51 AM
I know most folks on DIYSB are all about etching and vero and such, but I just thought I'd stick a note here that 1776 Effects released the PCB project for this today: http://1776effects.com/store/

It's red and has a bird. <3

mine just came in. psyched!! thanks jon!

Jon,
has anyone done a PCB of the Blue Warbler?

Quote from: JohnForeman on January 09, 2014, 02:57:27 PM
Jon,
has anyone done a PCB of the Blue Warbler?

Not yet. Jacob at JMK has been working on it, but there turned out to be some PCB-specific issues (one of the PCBs had some sort of ground bleed distortion, and Jacob told me the second layout had some other issues like hiss). It's getting a small redesign (which will only have the vibe mode and a simplified envelope), and I hope the PCB will finally happen this year.

 :(
I'm having a bad time trying to get this to work. The Schematics on page one are correct? I have a lovely tremolo but no harmonic tremolo.
I tried just taking out the switch and having that 2.2 nF (C7) cap go to ground; No change. Just a normal tremolo, depth, rate, and volume all seem to be up and running correctly. I've built this three time on my breadboard today. I'm not saying I'm not making a mistake, I probably am :icon_redface:, I just want to check. First post Schematics are good? Its a nice tremolo so far :-X

Quote from: 9520575 on February 02, 2014, 10:06:34 PM
:(
I'm having a bad time trying to get this to work. The Schematics on page one are correct? I have a lovely tremolo but no harmonic tremolo.
I tried just taking out the switch and having that 2.2 nF (C7) cap go to ground; No change. Just a normal tremolo, depth, rate, and volume all seem to be up and running correctly. I've built this three time on my breadboard today. I'm not saying I'm not making a mistake, I probably am :icon_redface:, I just want to check. First post Schematics are good? Its a nice tremolo so far :-X

Check your voltages for Q3, if it's less than 2.5V it might not turn on. Since it's on a breadboard, just interrupt any connection to Q2 or remove that transistor so you can get the treble band working. Check to make sure your vactrol is working and oriented correctly. Make sure the LDR for Q3 is connected to both the gate and ground (remember, it's the gate bias).

???  :icon_redface: So, I built it again. Check voltages (replaced all the J201s for good measure.) Still the same. Then, I decide to replace the op-amp. Well man all of a sudden the treble is kicking in. There is all little bit of phasing happening. Its working, well. Its fairly mild, nothing close to yours in the demo. I did switch the order of my vactrols to see if maybe I had reversed the order. Whoa, definitely not what was wrong, the depth was basically on or no sound.  SO, I'M WAAAYYYY closer now. I'm going to play around with the resistance to the LEDs. I feel like I'm headed in the right direction. I replace the op-amp with a JRC5448, it was instantly different, treble side kicked in. Although it isn't very strong, like I said. So, bad OP AMP or... something...

Quote from: 9520575 on February 03, 2014, 09:27:33 PM

???  :icon_redface: So, I built it again. Check voltages (replaced all the J201s for good measure.) Still the same. Then, I decide to replace the op-amp. Well man all of a sudden the treble is kicking in. There is all little bit of phasing happening. Its working, well. Its fairly mild, nothing close to yours in the demo. I did switch the order of my vactrols to see if maybe I had reversed the order. Whoa, definitely not what was wrong, the depth was basically on or no sound.  SO, I'M WAAAYYYY closer now. I'm going to play around with the resistance to the LEDs. I feel like I'm headed in the right direction. I replace the op-amp with a JRC5448, it was instantly different, treble side kicked in. Although it isn't very strong, like I said. So, bad OP AMP or... something...

What vactrols are you using? What's the on/off resistance you're seeing? What color LED are you using for the indicator? (It must be diffused, not superbright).

Quote from: midwayfair on February 03, 2014, 09:49:56 PM

Quote from: 9520575 on February 03, 2014, 09:27:33 PM

???  :icon_redface:

What color LED are you using for the indicator? (It must be diffused, not superbright).

Oh you mean i should use a diffused LED like it clearly states. NOT the clear bright, overhead planes can see me signalling LED, I'm currently using?
Oops...


I'm using the vac from small bear you link to in the first post.

Hi all.  I picked up the Cardinal PCB from 1776 and have it built and sitting on my bench right now.  It seems to work as intended, but I have a question about the following note from the build doc:

QuoteQ3 will sometimes overdrive slightly with high output pickups or a boosted
signal -- this is normal and simulates some of the breakup found in the
amp circuitry.

I'm getting quite a lot of "breakup" no matter where I put the Cardinal in my chain (front of amp, effects loop, first/last/alone, etc.).  It's not unpleasant, but I literally can't get clean tones unless I roll my guitar volume way back (below ~5).  This is with humbuckers wound to ~8k.  Is that expected?  And if so, is there a way to give the Cardinal more clean headroom?

If it helps diagnose or troubleshoot, I socketed R7 and R9 and ended up with 8.2k in both for the following bias voltages: Q1 8.21/0.33/0v, Q2 7.16/0.20/0v, Q3 3.27/0/0v.  These are about as close as I could get to the spec'd bias with what I had on hand.  I also tried the suggestion about pulling Q2 in order to isolate Q3 and bias by ear: with Q2 pulled and while trying R9 values from 4.7k through 10k, the volume increased but the distortion was pretty much constant.  Conversely, with Q3 pulled the output was quite clean.

If it matters: I'm using a TL072CP for IC1, a J201 for Q1-Q3, and a VTL5C1 for both vactrols (all sourced from smallbear).  
 
I'm new to these forums and relatively new to building pedals, so I may be overlooking something really obvious or fundamental.  Any feedback is appreciated,

--Matt

Hey, Matt, I posted this over on Madbean, but I forgot to add it here (sorry!):

---

The Vp of a J201 is ~0.5-1V peak to peak. This is the voltage swing it can accomplish before clipping. (Clever folks will also notice that it's typical of the source voltage when used as a buffer, and a big reason J201s make lousy input buffers for clean circuits.)

It's noted in the build doc that 2n5457 will sub in all three transistors without rebiasing (typically -- Q3's drain resistor might still need some adjustment, especially if you're going for cleaner). The Vp of a 2N5457 is closer to 1.5V, so you can get a much bigger input voltage swing before clipping is heard. The sacrifice is lower output (about less than half the available gain), but the circuit has gain to spare, including some wiggle room on Q1 (you can raise its drain resistor o get closer to 6V if you want).

---

Essentially, here's what happened:

First, I designed the effect around J201s from Tayda before I (and many others) realized they were pretty much all way below spec. I should probably ask Josh if he wants to just make the 2N5457s standard now.

Second, Q3 is odd, in that I was very stingy with its biasing. I did it that way in part because the added distortion adds content up where the harmonics are occurring, but many people building this wish I hadn't done that. :)

Here's what I'd do: Use a 2N5457 for Q3 at the very least, and raise its bias to around 4-6V (just decrease the 4.7K a hair, 3.3K usually does it in mine).

Hi Jon.  This is good news and great information, thank you!  I'll order some 2N5457s, re-bias Q3 as suggested, and see where that leaves me.  Thanks again, --Matt

 Such a clever way to create a new sound from the old tremolo. My question is about the indicator LED and Vactrol LEDs. I recently built this on the 1776 pcb.

I found the main tremolo section worked perfectly but the high pass section hardly trembled at all. Multimeter could read the changing resistance of Vactrol 1, but Vactrol 2 seemed to not be changing at all. I disconnected the low pass side completely (lifted one leg of the LDR) so I could hear the high pass side by itself. Then I jumpered the current limiting resistor for the second vactrol and then I could hear the treble throb, subtly. The main channel provides complete silence on the wave troughs with depth set high, but even with the CLR jumpered the high pass side is just gentle.

I thought "with the three LEDs in series are those CLRs necessary?" I thought maybe the intention was to provide lower voltage to vactrol 2 for a more subtle effect. I breadboarded the three LEDs and CLRs as per the schematic (with normal LEDs replacing the vactrols), and they seem to be equal in brightness. So the designer had his reasons...

Don't you really only need one resistor on the end of the three series LEDs?  The 9 + volts already go through a diode and a 100ohm resistor first n the power section and each LED drops around 2v.

I am thinking of replacing vactrol 2. (I am using the recommended VTL5C1, and I bought extra.) Should have breadboarded first!

Also: Why diffused on the indicator? I am not aware of any reason why a diffused would behave differently than a clear. Or why a 3mm should have different fv than a 5mm. On the other hand, color would seem to be important. I first used a blue one and found a red seemed to work better, lower voltage drop, leaving a little more juice for Vactrol 2.

Quote from: idy on March 25, 2014, 08:23:56 PM
Such a clever way to create a new sound from the old tremolo. My question is about the indicator LED and Vactrol LEDs. I recently built this on the 1776 pcb.

I found the main tremolo section worked perfectly but the high pass section hardly trembled at all. Multimeter could read the changing resistance of Vactrol 1, but Vactrol 2 seemed to not be changing at all. I disconnected the low pass side completely (lifted one leg of the LDR) so I could hear the high pass side by itself. Then I jumpered the current limiting resistor for the second vactrol and then I could hear the treble throb, subtly. The main channel provides complete silence on the wave troughs with depth set high, but even with the CLR jumpered the high pass side is just gentle.

I thought "with the three LEDs in series are those CLRs necessary?" I thought maybe the intention was to provide lower voltage to vactrol 2 for a more subtle effect. I breadboarded the three LEDs and CLRs as per the schematic (with normal LEDs replacing the vactrols), and they seem to be equal in brightness. So the designer had his reasons...

Don't you really only need one resistor on the end of the three series LEDs?  The 9 + volts already go through a diode and a 100ohm resistor first n the power section and each LED drops around 2v.

I am thinking of replacing vactrol 2. (I am using the recommended VTL5C1, and I bought extra.) Should have breadboarded first!

Also: Why diffused on the indicator? I am not aware of any reason why a diffused would behave differently than a clear. Or why a 3mm should have different fv than a 5mm. On the other hand, color would seem to be important. I first used a blue one and found a red seemed to work better, lower voltage drop, leaving a little more juice for Vactrol 2.

"Diffused" is usually red, orange, yellow, or green. I know there are super bright blue diffused (I have a bunch), but those are kind of rare. I guess we should have specified the color. :) Anyway, it can't be blue or white from what I've tried; the total voltage drop seems to mess things up a little, and I couldn't get any depth out of it. As you discovered, red works better. Green is still fine and is actually the color I tend to use.

It says 3mm in the schematic because in Eagle, the part has the measurements. In Josh's PCB, it says 3mm because that's the size of the pad. The size doesn't matter.

As far as the depth problem on Q3:
It's possible to have a vactrol out of spec enough that it won't have on resistance low enough to pull the gate of Q3 low enough to trem completely. It's unfortunate, because although vactrols are more consistent than most discrete LDRs, they are a heck of a lot more expensive if they have to be replaced. I have one VTL5C1 in my box of parts right now that works on Q2 but not on Q3, since the light resistance never seems to get below 30K and most of the time isn't below 100K (!).

But before you go pulling an expensive part off the PCB, set the depth to minimum and measure the resistance of the LDR side of vactrol 2 and compare it with Vactrol 1.

You can also try simply jumpering the indicator LED to see if that helps. (If it does, there's another way to wire a rate indicator LED: Just run some wire from pin 7 to an LED's anode, and connect the cathode to ground through a CLR. Ugly, I know, but still probably better than desoldering an $8 part.)

The extra resistors to ground increase the length of time the LED spends on the dark swing. You can see something similar in the Tremulus Lune, from which the LFO in this is derived. The cascading values were needed to keep the LEDs similar brightness. One thing that happens with them is that they tend to soften the on-off, so the sine wave side is a lot softer than the original lune's (the extra LED helped, too).

On the other hand, Vactrol 2 doesn't need dark resistance any where near as high as vactrol 1, so there are actually other optocouplers that will work. If you have some other stuff in your bin, measure a couple and see if you have one with light resistance below 5K and dark resistance anywhere above, say, 500K (but preferably above 1M) and a relatively far on/off time. That should provide a sufficient range. Just a heads up: I can tell you for certain that the NSL-32xxx ones DON'T work, though; they never get dark enough and seem to have a turn off time much slower than their datasheets claim.

Thank you, you answered all my questions and got me to ask better ones. I really admire the patience and love that go into giving an idea away and teaching everybody and their dog to make it work. I'm now satisfied that both sides are treming in contrary motion.  I still don't hear the phasey sound I heard in the demos. I have a few other boards and will definitely breadboard before no 2... and read the whole thread again.

Quote from: idy on March 27, 2014, 10:02:56 PM
Thank you, you answered all my questions and got me to ask better ones. I really admire the patience and love that go into giving an idea away and teaching everybody and their dog to make it work. I'm now satisfied that both sides are treming in contrary motion.  I still don't hear the phasey sound I heard in the demos. I have a few other boards and will definitely breadboard before no 2... and read the whole thread again.

Try this:

Remove the 150pF cap from Q1.

Increase the 2n2 cap connected to the switch to 4n7.

Quote from: midwayfair on March 20, 2014, 06:25:55 PM
Here's what I'd do: Use a 2N5457 for Q3 at the very least, and raise its bias to around 4-6V (just decrease the 4.7K a hair, 3.3K usually does it in mine).

Hi Jon.  Hi all.  I wanted to report back on my quest for a bit more clean headroom on my Cardinal build.  So I swapped Q1-Q3 to 2N5457s from Smallbear and rebiased as follows (w/ a 9.21v power supply):

Q1 7.90v w/ 1.2k R4
Q2 6.89v w/ 3.6k R7
Q3 5.57v w/ 1.2k R9

Do these values seem reasonable?  I'd expected to fiddle with R9 to get the Q3 voltage up as suggested, but I was surprised at how much I needed to tweak R4 to get Q1 back near 8v.  The end result appears good--much more clean headroom, an overall more useable circuit for my guitar/amp (with GORGEOUS harmonic tremolo :icon_mrgreen:)--but I wanted to sanity-check the numbers.

Thanks again for any help,

--Matt

Quote from: mwnovak on March 28, 2014, 01:01:23 PM

Quote from: midwayfair on March 20, 2014, 06:25:55 PM
Here's what I'd do: Use a 2N5457 for Q3 at the very least, and raise its bias to around 4-6V (just decrease the 4.7K a hair, 3.3K usually does it in mine).

Hi Jon.  Hi all.  I wanted to report back on my quest for a bit more clean headroom on my Cardinal build.  So I swapped Q1-Q3 to 2N5457s from Smallbear and rebiased as follows (w/ a 9.21v power supply):

Q1 7.90v w/ 1.2k R4
Q2 6.89v w/ 3.6k R7
Q3 5.57v w/ 1.2k R9

Do these values seem reasonable?  I'd expected to fiddle with R9 to get the Q3 voltage up as suggested, but I was surprised at how much I needed to tweak R4 to get Q1 back near 8v.  The end result appears good--much more clean headroom, an overall more useable circuit for my guitar/amp (with GORGEOUS harmonic tremolo :icon_mrgreen:)--but I wanted to sanity-check the numbers.

Thanks again for any help,

--Matt

Those all look fine. The biases aren't critical, and especially not on Q1 -- it's just there to provide high input impedance and bump up the gain to make sure it's above unity (really, a J201 was never the best call there, but I wanted to simplify the bill of materials). You could have left R4 the way it was (it probably would have settled near 6.5-7V). I gave Josh the voltages for the build doc so people could have some idea if they were even close to my original build.

I wonder if at this point, I should give Josh a new bill of materials that will run on 2N5457s instead of J201s. Everyone including me seems to like those better.

Folks, I'm going to say that the Macron clones can't he used in the cardinal with the values shown. I have a friend who is going to help fix the issue, since he has two built with both sets of vactrols (and he says that the Macron photocells sound completely different and have much less depth). If we discover a solution, I'll be sure to post it here.

Quote from: midwayfair on March 25, 2014, 10:06:22 PM

Quote from: idy on March 25, 2014, 08:23:56 PM
Such a clever way to create a new sound from the old tremolo. My question is about the indicator LED and Vactrol LEDs. I recently built this on the 1776 pcb.

I found the main tremolo section worked perfectly but the high pass section hardly trembled at all. Multimeter could read the changing resistance of Vactrol 1, but Vactrol 2 seemed to not be changing at all. I disconnected the low pass side completely (lifted one leg of the LDR) so I could hear the high pass side by itself. Then I jumpered the current limiting resistor for the second vactrol and then I could hear the treble throb, subtly. The main channel provides complete silence on the wave troughs with depth set high, but even with the CLR jumpered the high pass side is just gentle.

I thought "with the three LEDs in series are those CLRs necessary?" I thought maybe the intention was to provide lower voltage to vactrol 2 for a more subtle effect. I breadboarded the three LEDs and CLRs as per the schematic (with normal LEDs replacing the vactrols), and they seem to be equal in brightness. So the designer had his reasons...

Don't you really only need one resistor on the end of the three series LEDs?  The 9 + volts already go through a diode and a 100ohm resistor first n the power section and each LED drops around 2v.

I am thinking of replacing vactrol 2. (I am using the recommended VTL5C1, and I bought extra.) Should have breadboarded first!

Also: Why diffused on the indicator? I am not aware of any reason why a diffused would behave differently than a clear. Or why a 3mm should have different fv than a 5mm. On the other hand, color would seem to be important. I first used a blue one and found a red seemed to work better, lower voltage drop, leaving a little more juice for Vactrol 2.

"Diffused" is usually red, orange, yellow, or green. I know there are super bright blue diffused (I have a bunch), but those are kind of rare. I guess we should have specified the color. :) Anyway, it can't be blue or white from what I've tried; the total voltage drop seems to mess things up a little, and I couldn't get any depth out of it. As you discovered, red works better. Green is still fine and is actually the color I tend to use.

It says 3mm in the schematic because in Eagle, the part has the measurements. In Josh's PCB, it says 3mm because that's the size of the pad. The size doesn't matter.

As far as the depth problem on Q3:
It's possible to have a vactrol out of spec enough that it won't have on resistance low enough to pull the gate of Q3 low enough to trem completely. It's unfortunate, because although vactrols are more consistent than most discrete LDRs, they are a heck of a lot more expensive if they have to be replaced. I have one VTL5C1 in my box of parts right now that works on Q2 but not on Q3, since the light resistance never seems to get below 30K and most of the time isn't below 100K (!).

But before you go pulling an expensive part off the PCB, set the depth to minimum and measure the resistance of the LDR side of vactrol 2 and compare it with Vactrol 1.

You can also try simply jumpering the indicator LED to see if that helps. (If it does, there's another way to wire a rate indicator LED: Just run some wire from pin 7 to an LED's anode, and connect the cathode to ground through a CLR. Ugly, I know, but still probably better than desoldering an $8 part.)

The extra resistors to ground increase the length of time the LED spends on the dark swing. You can see something similar in the Tremulus Lune, from which the LFO in this is derived. The cascading values were needed to keep the LEDs similar brightness. One thing that happens with them is that they tend to soften the on-off, so the sine wave side is a lot softer than the original lune's (the extra LED helped, too).

On the other hand, Vactrol 2 doesn't need dark resistance any where near as high as vactrol 1, so there are actually other optocouplers that will work. If you have some other stuff in your bin, measure a couple and see if you have one with light resistance below 5K and dark resistance anywhere above, say, 500K (but preferably above 1M) and a relatively far on/off time. That should provide a sufficient range. Just a heads up: I can tell you for certain that the NSL-32xxx ones DON'T work, though; they never get dark enough and seem to have a turn off time much slower than their datasheets claim.

I had exactly this problem! I just built a Cardinal board from 1776. The tremolo effect works but, the phasey trem was not sounding correct. I have built a similar project before so I'm familiar with what this should sound like. After futzing around for a bit I realized the treble side was not changing in volume.

I removed the the Vactrol on the bass side and I only hear trebly guitar no changing in volume. I removed the vactrols, they were in sockets, and inserted two LEDs. The bass side, VAC-1 on the 1776 schematic, cycles from bright to dark correctly. VAC-2 on the treble side is dark most of the time, with a tiny blip of light for each cycle. Obviously this is the problem.

I'm trying to decide what to do. I'm using VTL-5C1 for the vactrols, these are the correct part. It seems the problem has to do with the current driving the LEDs, not the LDR. I measured R16, 17, and 18, these are all the correct values. Seems there is not enough current to drive the third LED in the chain.

I am using a 5mm LED for D2, the parts list mention this should be 3mm. This is a random red LED, not a super bright, from the bin. Now that I've gotten this far, I'm thinking D2 might be the culprit. Adding a jumper across D2 should be a simple test...

Sure enough, as soon as I jumper D2 VAC-2 lights up and cycles like it should. I inserted the VTL-5C1s again, turned the speed up to max and measured the voltage across each LED.

• D2 1.76V
• VAC-1 1.5V
• VAC-2 0.8V

I'm guess the voltage drop across D2 is too great. I can try other LEDs here. I'm wondering if there is anything else I can do to increase the current to VAC-2?

You can move the indicator LED and make just a speed indicator LED (no depth indication) by connecting the anode to pin 7, cathode to a resistor, and the other leg of the resistor to ground.

You might also try a different op amp, sometimes that's an issue in this oscillator.

You can try fiddling with the resistors near the LEDs. They change the "dark" cycle time for the LEDs.

The more I look at the LEDs I feel like the two LEDs in the LDRs should be in parallel. In series the last LED is in a spot where the operating voltage is very narrow. There is a voltage drop across each LED. The last in line getting barely enough enough to turn it off and on. This also makes the depth control less effective.

With the LEDs in parallel they both get a better range and more current.

Another alternative might be to use a single LED driving two LDRs.

Quote from: soggybag on August 02, 2014, 12:36:47 AM
The more I look at the LEDs I feel like the two LEDs in the LDRs should be in parallel. In series the last LED is in a spot where the operating voltage is very narrow. There is a voltage drop across each LED. The last in line getting barely enough enough to turn it off and on. This also makes the depth control less effective.

With the LEDs in parallel they both get a better range and more current.

Another alternative might be to use a single LED driving two LDRs.

If you put them in parallel, you have to match the Fv in vactrols, which means you need a pile of vactrols around. 5C1s are really expensive, so that's just making an expensive project even more expensive. If they don't match, one will suck up most of the current and the other will barely turn on. I've tried this in the past.

If you want there to be no difference in voltage between the two vactrol LEDs, remove the 4.7K resistor between the indicator LED and the first vactrol. The voltage drop across the two remaining LEDs will be identical then, because they'll be in series. (Or R16 in the 1776 schematic, which is backwards from mine.) But then you have to deal with the fact that you don't WANT the same on/off time for both FETs, because they create the tremolo effect differently. But by all means, go ahead and try it, because it's your pedal that you're building. If you're using the PCB, you can just lift one leg of the vactrol and run a little wire to tie the cathodes together and add a jumper to tie the anodes together.

And I'm not trying to be rude, but your comments are making it sound like the circuit doesn't work, when there are dozens of properly working builds out there (just going by build reports) built on the schematic. The only issues I've ever run into with the vactrols is (a) the Smallbear Macron work-alikes don't work alike and (b) I had an actual dud vactrol once and (c) there's not enough current to use a superbright for the indicator.

No offense taken. I'm just trying to discuss the subject. It seems like what you have here works but, it requires finicky part choices. I'm just suggesting there might be room for improvement. People have been trying to improve the Fuzz Face for 40 odd years now.

I'm also trying to discuss this to solve my issues. I have the same problems idy seemed to have. I'm using a 1776 PCB, and VTL-5C1 for the vactrol which is the correct part.

If the LEDs are in parallel but, each have their own current limiting resistor current should be divided between them and they will both light up without being matched.

I'm trying to puzzle out the math involved. I'm sure there will be a few mistakes here. I'm guessing we get about 4.5v to 9v at D2. Each LED has roughly a 2v voltage drop. After the first two LEDs there is very little left to drive the third LED.

Just a thought,
If the LED's are in series, but you want to tweak their relative brightness, and you know which one needs to be less bright - put a trimmer resistor across that one. A 5k trimmer should give enough range. This resistance will bypass some current around it, making it weaker.

Jim

I'm hoping to build a tap-tempo enabled version of this in the new year (I have a friend coming from the US who is gonna ferry back a Small Bear order for me).  I found the schematic a few pages back, but wanted to double-check that I can use a 78L05 in place of the 7805 voltage regulator.  The current draw on the TAPLFO and LEDs won't be higher than 100mA, right?

Quote from: solderfumes on November 27, 2014, 11:00:47 PM
I'm hoping to build a tap-tempo enabled version of this in the new year (I have a friend coming from the US who is gonna ferry back a Small Bear order for me).  I found the schematic a few pages back, but wanted to double-check that I can use a 78L05 in place of the 7805 voltage regulator.  The current draw on the TAPLFO and LEDs won't be higher than 100mA, right?

That should not be a problem. I have been using the TAPLFO with 2 Optocouplers fed by a 78l05 in a different tremolo and have never had issues. (I never measured the current though, but it's been running every day for more than a year...)