Clyde Mccoy Wah Circuit Board

[joegagan]

ha! hi ed, good to see you. good old days, right?

axeman, i actually had registered here last year but never posted. thanks for the invite!

yes, RG's article is good however dated and overworked. he researched it, posted it and moved on. a lot of things have been invented and discovered since he wrote it.

at gus smalley's urging, i delved into modeling wha circs in spice last year. we found , to our delight that the program predicts what the circuit will do very accurately. it has become a staple of my designing and building.

couple notes:
1.sharp peaks sound good. broad flat peaks make a boring wah.

2. inductor mh is not that big a deal ( can deal with mh by changing sweep cap ), inductor R is more critical to Q in actual use. 35 to 50 ohm is a nice target. you can add series R to a low R inductor, not so good to try and lower a high R inductor.

3. everything affects everything else. trying to tune a wah is like playing 5 games of chess at the same time. there is no free lunch, easy to move the sweep up or down but is very hard to widen it.

4. i like low gain trans better than high gains. my faves are 160 - 200 for Q1, 200 - 240 for Q2. simply altering gain of high gain trans by the normal biasing tricks has a different sound than low gain trans.

5.the old internet trick of using a .33 in place of one of the .22s going to the pot to simulate icar taper does not work in spice, and hasn't ever done anything i could discern in real life either. to get any kind of taper altering 'effect', the wiper cap needs to become 3 to five times larger than the other .22. at this point, other things get messed up ( see note #3 ).

6. pot taper is important not just for player feel but i think there is actually a tonal effect in how the cap to ground off inductor charges/discharges depending on the R going to either half of the pot at a given point in time. my theory is that 'fast' tapers may not ever get the cap fully charged as it goes by too quick.

[joegagan]

regarding # 3 above^

one of the major components to widening the sweep is all the parts in balance. it is a finicky filter.

this is what makes the boomerang so special. they have a really wide sweep when they have the correct pot in there. the engineers really knew what they were doing, and the gains of the trans had to be within 5-7% of spec in hfe to pull it off since they weren't trimmers to dial in each wah.

[SteadyEddie]

I actually invited him over here stedyeddie so he could be an active member.

It's great seeing Joe here. He really had some innovative fuzz designs a while back so ifj he applied that to wah I'm curious about what he found. Might get me to open up my mod-wah again and start tinkering...

[projectx102]

I have a few of those NOS polystyrene caps and a few of the Halo inductors that Dunlop uses in the Bonamassa wah. These are a great combination in my home built wahs.

[axeman]

I have a few of those NOS polystyrene caps and a few of the Halo inductors that Dunlop uses in the Bonamassa wah. These are a great combination in my home built wahs.

I would like to buy some, post some pictures.

[SteadyEddie]

Do the NOS polystyrenes sound any different than, say, the ones you get at Mouser?

[projectx102]

For those inquiring about the styrene caps, I used what I had in my personal builds and I sent the rest out to another pedal builder. As far as the tone of NOS vs newer, it' s kinda like NOS Iskra resistors vs newer types. They are somewhat warmer with less of a harsh top end. They sound less "plasticky" if that makes any sense.