Rotary type effect add-on for LDR Wah Pedals - Accidental Discovery

[PDGoss]

Hi all, I stumbled across something by accident some time back and figured I would share it. I was given a 1979 MuTron C-200 and while shining a little light in it my finger kept slipping off the button of the light. I engaged the wah and with my finger still slipping I noticed a unique phenomena that closely resembled a rotary effect. So, after some thought, I came up with the idea of adding (not to my vintage pedal) an Astable Multivibrator circuit that would would ramp up and ramp down an LED and the pulse rate is controlled via a potentiometer. I proto-boarded it and a friend needed the sweep on his Morley Distortion Wah adjusted so I slipped some extra length of wire on the LED, stuck it inside and I tried it out... failed to get sound clips, but the results were awesome.

This may not be new to anyone, but it was to me and I really dig discovering things by accident as well as creating new things of my own. I've done a number of things on the PB that I need to create schems for; but time is so thin it'll take me a while. They are tucked in the dark recesses of my brain; silly that I can remember 500 lines of programming code, a prototype circuit, etc., but forget to take out the trash. Wait... I'm clinically ADHD, that's my excuse and I'm sticking to it. lol.

[GGBB]

Did you point the LED at anything in particular?  Were you in wah or distortion mode (I would expect wah mode)? Since the Morley is LED/LDR based, it makes sense that a pulsing light would vary the amount of effect, just like moving the treadle does.  That would be a cool mod.  I think you could do something similar with a volume pedal to make it behave like a tremolo.  Now you've got me thinking about what I should do with my Morley wah-volume that is currently unused!

[liquids]

While I am a huge fan of simulation of circuits for frequency analysis...and while I am completely out of my league on both this particular circuit and with phasers/univibe circuits myself...filtering, in a more general sense, is by no means something unfamiliar to me...

At that...I think a lot of the whole pedal and DIY scene starts from a "take a classic and tweak it" perspective.  Sometimes, one can "re-create the wheel" in terms of the approach one takes to get an effect that is sonically similar to a "classic" sound. 

"Sonically similar" is sometimes as close as you can get to a particular circuit's sound, or the sound in your head that you associate with it anyhow, even when you DO duplicate the circuit (and in this chase, the mechanical/optical) similarities as closely as possible.

Stay with me now, if you can...

Like you did inadvertently - why *not* start with a clean sheet of paper?   

Maybe your wah is the "classic" approach for wahs which is a Band-Pass filter - a variable frequency peak, of which the frequency is being controled by foot.
However, it may be that this circuit instead takes the "inverse" approach...a variable 'notch' in frequency or frequencies rather than a "peak," of which the setting of the peaked or notched frequency/frequencies are controlled by foot. 

In general, that is what a phaser does.  The Univibe is unique, but to me, it is a specialized approach to phasing at it's over-generalized core.  The univibe was sort of trying to sound like a leslie - and it fails miserably at that to many ears and in many respects (even if not all).  But hey, what a great sound it makes!

Anyhow, whatever it is, go for it!  Make it sound good! Univibe, leslie, spinning, rotating, wahing around and around...go for it!   

Certainly, we know great sounds have been had by various classic pedals.  But, my gosh - with open ears and less A/Bing, it seems lunacy, to me, to think the "classic" circuits for wah/octavia/fuzz/phaser/univibe/chorus/etc can't be 'bettered,' particularly by "starting from scratch" or "completely different" sort of approaches than tweaking the "classic" circuit.

Some of the tones/pedals/effects we tout are hideous but nostalgic.  I love the sound (in doses) - but if someone told me that "that" guitar tone on 'Spirit in the sky" was simply AWFUL, I would have a very hard time attenting to invalidate their opinion as heretical, "classic" and "nostalgic" as that guitar tone is.

Heck, go figure out how you made that sound, and take it to the MAX.  Find the LFO that makes that circuit swoon with a sound that competes with - or puts to shame - the coolest univibe sound.  Let 'em call it heresy...let your speakers (and any customers) smile all along at the sound just the same.

I find it funny that the "cheap mans univibe" clones are all, more or less, phase-45 circuits. Really - the circuit approach of a univibe and a phase 45 are night and day.  4 stage phasing vs 2 stage phasing.  Optical vs fet.  And so on.   But ~2002 I went to a guitar center to try 2 on-the-market and well-regarded univibe clones.  In the case was a "what the heck is that!!" - phase 45.  Had never heard of it.  It had been hack-modded for a 9v jack.  I put all three side by side. I went home with the Phase 45 - it had the sound "in my head."  Maybe it was just that one phase 45 that sounded better than each of the specific units they were being evaluated against that made it the "shootout winner."  I dunno, and don't really care. 

That phase 45 circuit has been on my pedalboard and/or in my pedal ever since, set to one very specific range of knob setting.  Many people who knows "univibe" or "the univibe sound" says something about Trower or Hendrix (etc.) when I turn it "on" and play around with the "sonic palate" which that oblong, swirling, brooding sound it creates.  The phase 45 is a great phaser on it's own, even if it's a one-trick pony.  It does it's own take on a quirky "faux-vibrato" at fast speeds, and if someone wanted "that" univibe sound, the phase 45 might offer something completely different - to one person altogether better, to another, altogether fake-plastic.  Etc. 

Forget the "strange approach to rotary effect" or "unorthodox circuit" or "highly limited one trick pony" perspective on whatever you come up with, altogether, if you can. You seem to like the sound, and I think that you would probably not be the only one...share it with the world via circuit, or via sales, or via grins...dig it.