I'm at the lab currently, trying to install a "Bright" tone modification switch, using a DPDT switch. This should put a capacitor in parallel with the potentiometer, but it is just making my amp really noisy so far. I double-checked my wiring, and I think I have 1a bad design.
I checked to see if the DPDT switch was causing all the noise by taking the wiring out of the pot, and the switch circuit was causing all of the noise. Now to debug.
I think a root cause could be the type of capacitor I am using could be wrong. The modification called for a 120pF silver mica capacitor, which I used earlier to replace a broken cap. I am currently using a 100pF ceramic disk cap, which seems to handle higher voltages worse. Amps seem to use these silver mica capacitors exclusively because of their reliability and ability to handle high voltages.
I tried changing the capacitor to an electrolytic capacitor, with the same negative results as before.
I tried using the SPST for a few things. I strapped a 1Megaohm capacitor across the terminals, and then hooked that up to the input and ground of the cap. More buzz.
In other words, today, I tried a bunch of things, and they all just created a bad hum for the output. I have reverted it all back to the way it was at the beginning of the day, and I'll start again tomorrow.
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