DIY Stompboxes > Building your own stompbox

modifying a crybaby


Hi, Is it possible to modify my crybaby so that it works like the Morley Bad horsie (steve vaï). This pedals is switched on when you put your foot on it, and is disengaged when you take your foot off...
Any suggestions on how I can mod this?

Mike Burgundy:
first off you'd have to rework the crybaby to operate like Morley's wah's do (LDR and lightshield instead of a pot). Anderton's silent-pot mod will get you there. Apply FET switching, or even relays for on/off switching.
Then there's the electronics that detects a *change* in position and kicks in the switchig bit. Can be done in a lot of different ways - magnetic, optical, whatever. The key is to get something that goes from 0 to 1 on movement and stays there until there's no movement for a set number of (milli)seconds.
You'd effectively be making a whole new wah - no sense in modding the existing one that extensively, and without bad horsie schems, maybe some security sensor chips might work ;)

the schematics of the bad horsie are here:

Can anyone help me with this, 'coz I don't know wich parts take care of the switchless on/off design.


Mike Burgundy:
Looks like the switching is the same as their "silent switch" system, but with a detector LDR/LED instead of a switch.
it's actually more rudimentary than I thought...
I forgot the BadHorsie was a Crybaby-style inductor wah, nice.
Let's see. from the input, there's a standard buffer.
This feeds the wah ckt, and goes to the switching FETs (F1, 2). These are always opposed to each other: if 1 conducts, 2 resists and vice-versa. This is what chooses between the wah ckt (2 conducts), or the direct buffer output (1 conducts). Led1 (L1 is always on, and looks at the LDR that controls switching (LDR1). Leds 2 and 3 only turn on when F2 is open: 2 points at the wah LDR, 3 is your indicator.
I'm a bit surprised that it's "just" a switch - you could do the exact thing with a mechanical switch. One set point for on/off, somewhere at the extreme end of the pedal's throw, that's it. I half expected a high-tech variation-detection-circuit-thingy.

This will work without modding the wah to an LDR-driven one: Keep the pot, just incorporate the switching FETs control ckt, and the 3 buffer opamps to keep the FETs well set-up.
Basically, cut the circuit at R12 and C14, drop in your own wah.
You can leave out one of the leds/tranny/resistor (say around L2), you don't need it anymore. Use L3 for an indicator.
You need to construct a lightscreen that moves when you move the pedal - either vertically, or you might want it to rotate on the existing pot axle. Mount the Led L1 and LDR1 opposite each outher, so that the screen shields them from each other, unless the pedal is in use (meaning the pot is slighly rotated.)

Thanx, I'll try to figure out by tomorrow what you just meant, and will post my questions by then.

Thanx for helping me. :lol:


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