The Waschillator - LFO + op amp wah

[culturejam]

Thought you guys might get a kick out of this one.

I always liked the original ROG Phozer's base sound, but the LFO wasn't really that useful at lower speeds. So I took the basic idea, which is the Idiot Wah + LFO, and kicked it up a notch. Instead of the Phozer's input JFET buffer, I went with an op amp buffer, and since there's an extra amp in the package, I also added an output buffer. The LFO is the same one I've been tacking on to everything the past couple years (from the STM). For the variable resistor element, I went with the H11F1 opto IC. But a vactrol or LED/LDR would also work very similarly (and actually they sound better).

It's not a phaser. It's not a vibe. It's not a tremolo. I suppose it's most like a phaser with a dash of trem, but it's really not all that much like any commercially available modulation. Which is probably a good thing.

This was something I drew up and hoped worked when I ordered the proto board. And it does work quite well. Surely there are many mods and tweaks to be made to improve, extend, or expand the tones available. I offer this working, fun, useful circuit to the community to experiment with and renovate.

Sound clip of the circuit with the H11F1 opto is below. I recommend going with a vactrol or LED/LDR pair instead. The sound is more intense and with a wider sweep.




Populated board (some parts are surface-mount to save space).




And here's the schematic if anybody wants to play around with the circuit:

[Gigahearts_FX]

Cool circuit. Be nice to hear it with the LDR/LED combo

[culturejam]

Cool circuit. Be nice to hear it with the LDR/LED combo

It's similar, just more "depth" and a wider tonal change across the LFO sweep.

But I will be doing another demo with the LED/LDR.

[Chankgeez]

That sounds pretty nice & interesting, culturejam.

I'd bet it sounds great with fuzz too.

[pickdropper]

Damn, I am glad I get to witness your brain power on a regular basis. That's fun.

[Nocentelli]

Cool idea. if one used the opamp wah stage from deadastronaut's (or Morleys?) Lightwah, it would only require two dual opamps: Might try this afternoon. Thanks for the schem!

[kurmudgeon]

I love the sound towards the end with the rate up higher

[Jero]

Awesome! I was wanting to try something like this already, so the timing is nice.

[culturejam]

Here's the sound with LED/LDR:



Definitely sounds more like a wah and now nothing like a phaser.

[Chankgeez]

Yeah, sounds more like a wah. Still sounds pretty nice though.

[Sergiomr706]

Sounds so great! Congratulations on the design, I really dig it, by the way, could you please tell me about the led and ldr you used instead of the h11f1? I am thinking about subbing this HF in other designs for a homemade "vactrol" and Id like to make a design a stripboard for the wahscillator too.
Thank you!

[culturejam]

I used a cheap LDR from Tayda and a regular old 5mm red diffused LED.

[tabbycat]

hey culturejam, thanks for the post. neither vibe or phase, with added psychedelic sickbag. interesting.
looks a bit like the beavis' optochopto?



maybe it would be nice to vary this so it stuttered and wah'd.
or the caps tweaked so instead of wah-ing low to high freq the wah pot was replaced with a mid-scoop trim-pot, so the centre was sucked out of the tone and then pushed back in. that would be nice and weird. that would be the anti-wah.

[culturejam]

It's theoretically similar to the OptoChopto, being a wah with an LFO to vary the sweep. But it's implemented quite differently (different LFO, different wah). The Chopto's LFO is one I tried many years ago. Can't get that thing not to make a ton of noise (not the good kind). It clicks like mad.

Adding a square-wave (stutter) is trivial. But it's not going to be all that square because the optical element doesn't react linearly (it turns on faster than it turns off).

[mathias]

This is so rad

You're cool with people building these up, culturejam? I'd really love to make my own.. I'm a fan of all things wobbly.