http://www.diystompboxes.com/pedals/schall.gif
Works.
I built this a couple of years ago using Radio Shack transformers for the inductors and I wasn't impressed with the sound. I finally broke down and bought a couple of Dunlop inductors and put them in tonight. What a difference! Now it actually sounds like my original one.
Never give up.
A friend of mine found an original one in the attic. it seems that someone tried to put a fuzz unit inside as well. Anyways, he wanted me to use the shell to build a clyde replica.
But, does the original unit sound good enough to restore?
What is that? I've never heard or seen it. It looks like a wha with two indductors? Is it sort of like the Bi-filter?
Rick: did you use a 100k neg.log. pot like in the schem?
It's a wah pedal with two different voicings. The first sounds pretty much like a regular Crybaby type wah, the second is more vocal, nasal, pukey (it's hard to describe).
I just used a regular 100k linear pot when I built it. I don't have any reverse log 100k pots so I'll probably just use a standard wah pot when I mount it in a shell.
If you have an old one it's definately worth restoring. They aren't worth what an old Vox wah is but they still have vintage value beyong, say, a current Dunlop wah.
I'm jealous. Loved those suckers. Had one and let it go. Oddly enough, never stuck one in front of a fuzz, so I have no idea what they do to one, relative to a more conventional wah.
How does it sound? Stick the tip of your tongue over your teeth and under your lower lip. Now try and say "Ow" by tensing the muscles waaaay at the back of your throat (I mean around your Adam's apple). That comes close.
Alternatively, if you can score a download of the classic "Soul Makossa" by Manu Dibango, that tune highlights the yoy-yoy setting on rhythm guitar.
I asked about that negative logarithmic 100k pot,
coz I happen to have a handful of them (unused, pinion attached!)
since that: "one of the saddest days in my life",
I`ve referred to in several wah-shell-threads...
btw: got 2 of those gray "yoy" shells without the guts...
Okay, I've played around with this a bit more and I have a few things to report.
First, I noticed that I changed a couple of resistor values on my schematic and on the pedal I built. I don't remember specifically but I probably checked against my original one when I was first trying to get it to work and used the values I found there. The 10k from ground to the junction of the first inductor, a 10uF cap and a 470k resistor is changed to 100k and the 10k from 9 volts to the collector of the first transistor is changed to 15k.
I replaced the 47k at the input with a 50k pot, input to the wiper. This essentially gives me an input pot variable between 0/57k and 50k/27k. I also replaced the 4k7/6k8 combo at the output with a 10k volume pot. The output volume pot is nice for adding a little volume boost when the effect is engaged or taming the volume when the input put is turned up. Turning the input pot up added a little brittle distortion in addition the the extra volume. Might be helpful with single coil pickups (I tested with humbuckers).
Notice that the yoy-yoy switch just shorts a 1M resistor. After some fiddling with a trim pot I used a spdt centre-off switch to choose between 0 ohms (switch to one side), 1M (switch open) and 4k7 in parallel with the 1M resistor (switch to other side). Anything over about 10k in parallel with the 1M doesn't change the sound much.
I also used another spdt centre-off switch to add 1uF or 0.1uF caps in parallel with the 22nF cap that is in series with the second inductor. The extra sounds are only really noticable with the yoy-yoy switch in the full yoy-yoy (i.e. 1M shorted) position. A rotary switch to choose more caps would be worth doing too I think.
I would never have done any of these mods to my original one but they're great fun on a home built one.
Hmmm...
I got a new restoration project on my bench...(yey?)
I just got hold of a old schaller Yoy Yoy chassis but the pcb and thereby the circuit itself is missisng. The pot however is still there and it is a dual 100k! This do not match the schematic available. I have no reason to believe that this is not the original pot. Any info?
I was wondering what that bow wow yoy yoy was all about. This gives me a much better idea. 8)
Well? Tell us! :?