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Vintage threads from the first ten years

Re: Wah inductor source

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8/30/1999 4:47 AM
R.G.	Re: Wah inductor source Maybe... having been at this a while, I suspect that Maxwell's Demon may have tricks and traps laid for us that we haven't found yet . Cross your fingers!

8/31/1999 4:55 PM
Mark Hammer	I've got an old GP article by the ubiquitously peripatetic Craig Anderton, that involves retrofitting an opto circuit in a Clyde McCoy to replace the standard pot value and eliminate scratchy pots. I'll try and send you a scan of it ASAP. Surprised no one has mentioned it before now. As you might expect, this is still one more g&$#?!m reason to keep looking for CLM6000's.

8/31/1999 10:26 PM
R.G.	I have it. Didn't I mention that in the latest update to the Wah article? (I've done about five updates.) I did that to a Vox Reissue. Worked fine! I even put the rocker/pot on a 20 foot cable away from the wah circuit, still worked fine.

8/30/1999 10:31 AM
AMZ	Hammy, There is an article about modifying pot taper online at: http://www.muzique.com/lab/potmod.htm The S-taper in particular might be an interesting variation to try in a wah circuit. regards, Jack

8/30/1999 1:48 AM
CJ Landry	May I suggest using a small magnet to boost the saturation of the core when it is in its resonant region. I tried this on some dunlop crybaby wahs and it definitely made a difference but also increased the microphonics of the pedal to the point where feedback was a problem. However, finding the proper placement of the magnet made for some interesting sounds. CJ

8/31/1999 2:13 PM
paul perry	Good one CJ, I would never have guessed. Perhaps the mechanically dextrous could put a magnet on a shaft so you have another knob to turn! Or, just run a variable current down a spare winding, if there is any.

8/30/1999 4:33 PM

Why-a-duck? Why-a-pot?

All this kerfuffle about pots and tapers is because when a pot is used as the control element, you're basically stuck with what the pot physically consists of - the conductive element and its value/taper are what they are and that's it (taper-altering resistors notwithstanding).

Why not explore other non-pot alternatives?

In the early 80's, there was a "pedal" called Patch of Shades, that used a force-sensing pad instead of a pot. Wierd-looking thing - sort of like a stompbox with a vinyl welcome mat out front, but it worked well from what I understand.

It would be a modest (but feasible) amount of work to rig up a quasi-force-sensing pot by having a "see-saw" pedal with minimal travel (say 1/2 inch in either direction), that varied two force-sensing pads (one in the front and one in the back) made up from conductive foam. Go forward, and the front pad goes lower resistance as you press harder, while the rear goes higher resistance. Move your foot back, and everything goes the opposite way. Treat the jumper between them as a "wiper" and you're in business.

The tricky part, naturally, would be selecting the right amount of conductive foam to provide the appropriate resistance.

The operating/design constraints are that conductive foam gets, well, "crunchy" after a while (but a comfortably long while), and that there may be a wee bit of lag in registering "pot" changes, relative to a true pot.

The good side is that you can custom tailor this type of pot to whatever value and taper you want (including multiple "ganged-pots" of discrepant values and tapers), and that when it wears/crunches out all you have to do is cut yourself another piece of foam (assuming you can still get it 10 years from now).

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