wahs, pots, theories and new fad diet tips

[joegagan]

stay tuned, the diet tips are coming soon

in my never ending quest to find out why certain wah pots seem to 'feel' better than others, seem to actually spark more harmonic content in the circuit, i went on yet another multimeter quest.

i mapped out a particularly good 71 centralab 25k pot, a stock unit from a maestro boomerang. took readings every 7 degrees or so.
then i proceeded to try and mimic the taper in a 50k rev log pot ( boomerangs used some version of a rev log ) using tapering resistor tricks.

nothing i tried got me close enough to call it good.

then i hooked up a second multimeter to the other two legs of the pot. i found something a lot of you may already know, but something i took for granted. the readings on either side of the pot often exceeded the overall value of the pot. in other words, there was a spillover where at certain points, each side was getting more than simply the remainder of the other side minus the total value (or the inverse, you know what i mean).

when we think about what a pot does in a wah, this could have a pretty major effect on the tone that the filter is producing.

my other theory is that there is an actual time element involved due to the charge/discharge of the cap to ground off the inductor. if a pot has too fast a kink in the sweep, it may actually never fully charge the cap unless the player moves very slowly?

[R.G.]

What a lot of people forget is that there is a resistance of the wiper to the resistive track. This resistance is variable depending on the pressure of the wiper spring, the lubricant on the track (if any's left) and the condition/age of the conductive surface at that exact spot.

Makes for some interesting changes when the pot is used as a variable resistor. 

[joegagan]

thanks rg.

now, ass promised:

[Paul Marossy]

What a lot of people forget is that there is a resistance of the wiper to the resistive track. This resistance is variable depending on the pressure of the wiper spring, the lubricant on the track (if any's left) and the condition/age of the conductive surface at that exact spot.

Makes for some interesting changes when the pot is used as a variable resistor. 

Huh, I hadn't thought of that. That explains a few things...