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Special Sauce — Chorus, Vibrato, Doubler, Slap-Back Delay (with Demo)

Started by Aleph Null, May 23, 2023, 05:11:17 PM

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Aleph Null

Special Sauce is for when your tone needs a little something extra. It's a PT2399 based delay with envelope controlled pitch modulation that does chorus, vibrato, doubling, or slap-back delay.

The board is mounted to a wooden standoff with hot glue. It sounds precarious, but it's the best way I've found to mount vero builds.

This circuit is tuned for short, bright delays ranging from 30–150ms or so. The short delay time meant I could use the first CMOS stage of the PT2399 as an input buffer instead of for filtering. A Mosfet at the output supplies 0—35dB of gain. The real trick here is using the voltage on pin 8 as an envelope follower (as discovered by DeadAstronaut). Instead of applying the pin 8 voltage directly to pin 6, I used it to control a 2N5089 set up as a voltage sink. This makes the pitch bending much more pronounced, especially at shorter delay times.

Here's  a short demo:

Here's my layout, if anyone else wants to build it.


Pedal building is like the opposite of sex.  All the fun stuff happens before you get in the box.


Awesome design! The doubling is super sweet. Love that the range is useful on everything, I never manage that  ;D
I sometimes label builds rockwright

Aleph Null

Quote from: zombie_rock123 on May 23, 2023, 10:23:45 PM
Awesome design! The doubling is super sweet. Love that the range is useful on everything, I never manage that  ;D

Thanks! It was definitely hard to resist the temptation to add more range to the "Detune" control, but if I want octave drops on sixteenth-note repeats, I'll get my Clari(not) out.


Gordy Power
How loud is too loud?  What?


Aleph Null

Quote from: gordo on May 24, 2023, 11:54:26 PM
And what a cool demo!!

Thanks! I didn't want to futz with video editing software, so I had to find a way to do it in one take without any fancy title cards or captions. I also didn't want to yammer into the camera. My favorite demos have always been of the "less talking, more rocking" variety.


Wow that's really cool, and there are so many sounds with such a simple (dare I say elegant!) design!
I'd love to hear more vibrato (full wet, minimum delay) samples with various depth settings!
Amazing job, thanks for sharing!