SOLVED Wilhelm Scream: Unity Gain Issue

jeffwhitfield

Well-known member
Hey folks,

I'll post some pics of my build in a few but wanted to get this out. Want to make sure this is normal before going further with it.

Basically, I'm seeing an issue where the volume seems too low. To reach unity gain requires cranking the volume to around 3 o'clock. That's even with the Drive all the way up. By comparison, the Fingers Overdrive reaches unity gain at 9 o'clock. It's like night and day. Granted they're two completely different pedals....but I would think that with this one, unity gain would be closer to noon at the very least.

Is this normal? Or does it warrant further investigation? If it is normal, is there a way to boost the volume?
 
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Hard to help too much without the build docs - do you know if the Wilhelm is based on something more specific than just a TS? I would do two things if I had built this personally and wasn't getting unity gain - which I think is reasonable to expect, or at least close:
  • Make sure JFETs are legit and within spec
  • Confirm the pinout of 2SC1815s. The input and output amplifiers (I assume the input amplifier is a just a buffer but can't tell from the board, the output looks like a run of the mill common emitter) both use these, and I know I have had issues with pinouts with them before. I'd also confirm the resistance values on the output amplifier (the 10K and 510K) that set it's gain.
 
Alrighty folks, problem solved! Did a full continuity check and then started probing. Found that there was very little difference in tone off the middle of the tone knob. So...turns out that the cap running off of pin 2 of the Tone pot, the 220n, was mislabeled. Somehow a 22n got mixed up in my bag of 220n's. Weird. Anyways, once I switched it out, the Tone knob came to life and the volume did indeed increase. :D
 
Alrighty folks, problem solved! Did a full continuity check and then started probing. Found that there was very little difference in tone off the middle of the tone knob. So...turns out that the cap running off of pin 2 of the Tone pot, the 220n, was mislabeled. Somehow a 22n got mixed up in my bag of 220n's. Weird. Anyways, once I switched it out, the Tone knob came to life and the volume did indeed increase. :D
So how does it sound? (NOT that I'm interested in another overdrive or anything.....:))
 
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