Cardinal Tremolo (Vactrol-base Harmonic Tremolo) - schematic & discussion

[midwayfair]

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.

[pinkjimiphoton]

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!

[midwayfair]

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.

[pinkjimiphoton]

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!

[midwayfair]

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:

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:

PDF: https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/cardinal%20tremolo%20-%20bias%20mod%20version.pdf

[~arph]

  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.

[midwayfair]

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.)

[~arph]

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  <-- This one's good
http://www.uni-bonn.de/~uzs159/vcf4007_s.gif
http://www.diystompboxes.com/smfforum/index.php?topic=52472.0


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

[duck_arse]

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

[midwayfair]

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.

[~arph]

No problem getting them in europe

[pinkjimiphoton]

any eti projecst are always welcome.

while investigating the links arph posted, i found this:



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!!

[~arph]

Here is what I have in mind:

Hope its readable..



Not sure it'll work as drawn.

[pinkjimiphoton]

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

[midwayfair]

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. 

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.

[duck_arse]

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.

[pinkjimiphoton]

cool, thanks bro!

[pinkjimiphoton]

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:

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:

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)

[midwayfair]

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.

[pinkjimiphoton]

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

pm sent!