Shagpile - envelope-controlled lo-fi chorus/double tracking pedal

[BluffChill]

Can't believe I haven't posted this here yet!

I designed a PT2399 based double tracking pedal with a twist - the repeat is modulated by an envelope follower to make it wobbly and unstable in pitch like it's being played on an old tape player.

I was heavily inspired by Mid-Fi Electronics and his interesting uses of the PT2399.

It can go from gentle, quasi-chorus sounding drift to big, bendy, hissing tape-piling-up wobbles. It basically uses an envelope follower hooked up to the time pot to vary the resistance to ground and as a result is much more responsive to playing the longer you set the delay time to. You can also change the intensity of the envelope with the 'Flutter' control. I gave it a vaporwave inspired 80s/90s pink & green sort of vibe:



The Autumn Trap did a neat video demo of it too:

So you're probably wondering why I'm posting it here! Would anyone have any interest in the schematic? I'm always open to my suggestions for tweaks. I have boards available from my store too (in my signature) if you're interested.

[Kipper4]

Can we see the schematic please ?

[BluffChill]

Sorry for the delay and yes you can! Here's the original, most basic version:

[duck_arse]

from what I can make out on that circuit, you have R7 connecting to the [before the] rectifier before the smoothing cap - izzat right? part of its charm?

[BluffChill]

from what I can make out on that circuit, you have R7 connecting to the [before the] rectifier before the smoothing cap - izzat right? part of its charm?

That is indeed part of the charm! I fiddled with this a lot during development, and I originally had it connected up in a much more common way, like you'd find on an auto wah. But as I wanted some wobble in this, to emulate a wonky tape player, this worked better, so the unrectified signal allows the VCO of the PT2399 to modulate both ways. Pretty neat huh!?

[bowanderror]

I like your artwork & lettering, it fits the glitchy sound!

Could you go a bit deeper in to what duck_arse said about R7? I'm somewhat familiar with Doug's Clari(not) circuit, but I'm having a little trouble following the signal flow. Is there a vactrol in the circuit or are you using something else to generate an envelope? If I'm following this, you've replaced the Depth, Delay Time, and Tracking controls with one all-encompassing Tracking control. Does the Flutter control on the TL072 basically throttle the gain going in to the envelope?

It's an interesting take on an already cool pedal. I've said this before, but the Clari(not) is seriously one of the most accessible, understandable, and tweakable (non-drive/fuzz) circuits out there for DIYers. Doug really nailed it with the excellent pick sensitivity for subtle sounds, as well as the potential for totally whack-o sounds when you push it beyond that. And even though it's just a plain old PT under the hood, I've really fallen in love with it.

I see you've got a Deluxe version as well, what changes did you make for that?

P.S. I see you've got that lofi reverb as well. It would neat to see if you could apply the same envelope-control functionality to that circuit. You may have to hack into that Belton brick, though!

[duck_arse]

the usual method of enveloping takes the rectified signal from a smoothing cap, which removes some quantity of ripple from the rectified and provides a "decay" of some length. where R7 is connected means it will feed raw unsmoothed rectified pulses to the following, making for very dynamic modulation.

and welcome to the forum.

[BluffChill]

I like your artwork & lettering, it fits the glitchy sound!

Could you go a bit deeper in to what duck_arse said about R7? I'm somewhat familiar with Doug's Clari(not) circuit, but I'm having a little trouble following the signal flow. Is there a vactrol in the circuit or are you using something else to generate an envelope? If I'm following this, you've replaced the Depth, Delay Time, and Tracking controls with one all-encompassing Tracking control. Does the Flutter control on the TL072 basically throttle the gain going in to the envelope?

It's an interesting take on an already cool pedal. I've said this before, but the Clari(not) is seriously one of the most accessible, understandable, and tweakable (non-drive/fuzz) circuits out there for DIYers. Doug really nailed it with the excellent pick sensitivity for subtle sounds, as well as the potential for totally whack-o sounds when you push it beyond that. And even though it's just a plain old PT under the hood, I've really fallen in love with it.

I see you've got a Deluxe version as well, what changes did you make for that?

P.S. I see you've got that lofi reverb as well. It would neat to see if you could apply the same envelope-control functionality to that circuit. You may have to hack into that Belton brick, though!

Thanks!! Yes I was fairly influenced by the Clari(not) and Pitch Pirate but wanted something a bit simpler with minimal controls. Basically, the Tracking controls the delay speed like on a regular delay, and the 'Flutter' controls the intensity of the envelope generator, from subtle little wobbles to big bends. The harder you pick, the more bend you get!

The deluxe version basically adds a mix control (from completely dry to completely wet) and feedback, making it a bit more of a conventional delay. And it has pink LEDs!

The lo-fi Reverb (Ectoverb) doesn't actually use a Belton brick - just two PT2399s in series, which is more or less what's in a Belton anyway! It does have a modulation point on the board that you can play with but I've never actually got round to trying it. Maybe one day, or if anyone else wants to try...I have PCBs!

[Marcos - Munky]

Loved your build and the sound of it. Also, it's a simple circuit for what it does. Very nice!

[anotherjim]

It kind of does still control from the envelope in the usual way. The envelope cap (C3) voltage will affect how much current is drawn out of the PT2399 VCO tuning pin6.

[FUZZZZzzzz]

So, what about the Wax Ether pedal? Is it a stripped down version of the Shagpile? It sounds pretty cool. Have you tried it on bass and things like drummachines and synths as well?

[BluffChill]

It should handle synths and drum machines quite well - to be honest, probably better than guitars. As the output of a synth or drum machine is higher than a guitar, it should make the envelope which ripples the signal a lot stronger. I will run my MS-20 through it and get back to you!!