Long post - sorry... I have my 2204 working now. It broke a couple of weeks ago when I sold it to a GAS-head who treated it like a Thai sex therapist. He was twisting and turning every knob non-stop - spraying his cleaner in every pot & hole and using sandpaper in the inserts (I since learned that's a bad idea). After 30 minutes of that, it broke. I was there. First the high gain went dead, then the low. I had sold it to him without even plugging it in and it had been sitting a couple of years. Anyway, I felt obligated to take it back because he paid me a fair amount of $$ that day (two guitars + that head). So, we traded some things back and my goal was to make it as unbreakable as possible to resell it. So I got it working again and it was creamy and overdriven for three days. But, I was playing it and it just suddenly died again. effin'ell. It took a while, but I got it going again, but now it was clean and trebly even on the high input. Seeing nothing wrong I decided to just reflow V1 and lift the hot shield. Sure enough, found a teeny strand going from 5 to 6. Once I had it all re-flowed it sounded better than ever - but still trebly. Someone had posted a trick - a 3.2n cap between the purple wire and the impedance selector. I tried this and it seems to sound a lot better. QUESTION: DOES THIS NEED TO BE A CERTAIN VOLTAGE TOLERANCE? I usually build pedals and most of my caps are 25v max. I also took out the 1N cap on the master volume (treble bleed). It all sounds great. Now, I am not sure exactly why but now everything on the amp is far more interactive. I start getting overdrive at 4-5 on the preamp (high input) and a ton of it on 10. The tone stack can really tame any hum or push it louder than ever, (the range on each tone knob feels way expanded). This is not just a 2204 amp anymore, the range of possibilities is huge. So, all is great except - the amp is far more versatile than ever; but it is also less idiot-proof. The tone controls are way more interactive, so the mid will boost either the treble or the bass a LOT depending on which you have louder. (it seems to me it was more one dimensional before). Another continuing problem: If you turn the master all the way down you still get a bad loud oscillation. I love the amp the way it is - but to sell it, should I strive to get it back to idiot-proof? Or should I keep it more like the cool beast it has become? TL/DR: 1. I am still looking for more tricks to tame the treble in a 2204. 2. One trick I tried seems to have a strong effect; a 3.2N cap between the purple wire and the ohm selector. QUESTION: does that need to be a CERTAIN VOLTAGE RATING? I usually build pedals and most of my caps are only 25v max. 3. Any more surprisingly effective ways to tame treble on a 2204? 4. I replaced my Master Volume pot - why do I still get oscillation (a very loud squeal) every time I turn it to ZERO?