Mu-Tron to wah Projects?

[Diynot]

Was approached today by an acquaintance asking if it would be possible to make a Mu-Tron III based pedal that could be switched at will between EF and wah (with the use of an expression pedal). He wants his board real estate and cake too. Thinking on it my plan would be to (somehow) put the LDRs and expression jack on a footswitch. Lumitron schematic bits:
One big hurdle would be having an expression pedal with enough range to make it useful. The optos here are 5 ohm-10M ohm. Another is figuring out the actual physical wiring. Either way it’s sort of making my brain hurt. Does anyone know of an existing pedal/project with this kind of functionality or have any insights on how to make this happen? Seems like something @DGWVI would have fucked with at some point.

 

[pricklyrobot]

I’d guess that the filter probably isn’t responding to the entire range of that LDR. Like the filter’s fully open a while before the LDR hits 5R, and fully closed quite a bit before it hits 10M. Also the light source may not be bright enough to even get it to the 5R anyway.

Synth type filters usually have normal value pots in them. You might need to experiment to find the value that gives the best sweep. But I don’t think you have to try and track down anything like a 10M pot.

 

[Bricksnbeatles]

You could have the pot modulating the brightness of an alternate led for the LDRs

 

[Diynot]

You could have the pot modulating the brightness of an alternate led for the LDRs

Good suggestion. The Lumitron/MiniMu/Mootron all use a vactrol of one sort or another, but could def sub in something

 

[DGWVI]

Seems like something @DGWVI would have fucked with at some point.

I haven't - not much of a treadle guy, but

You could have the pot modulating the brightness of an alternate led for the LDRs

This is the way I'd go about it, and similar to how the Sweep control is implemented in the Lovetone Meatball. If you're using the Aion Lumitron board, it'd be as easy as replacing the Sweep trim with the treadle controlled pot.
In yours, you'd also want to switch off the envelope detector portion

Also- keep in mind your LDRs are in parallel with those 220k resistors