I recently built a 2204. It worked out well and sounded very good, but now I've begun modifying it.
My first mod was to convert it to JEL specs (below) and it came out very good, but my goal is to have something closer to a #34/#36 modded Marshall. Just in that range and tweaked to my tastes. I have now a JEl/#34 mod mix and though the tone and gain are in line with what I was expecting, the amp got noisy after the last few changes. Note, my original 2204 did not have a bright cap on the gain pot nor did I have a piggybacked 470K/500pf running from the normal input to gain pot.
Due to home construction, I don't have the luxury of adding one component and testing. To make this bearable, I have to solder in a few components, hope for the best, and then take the amp downstairs to test. I'm getting a workout
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The noise is a fast ticking and a squealy squirrely sound. It's not over the top, but definitely not something I would want.
Changes I made before noticing this
2200pf bright cap on gain pot
470K/500pf from normal input to gain pot (using shielding wire) *I also tried 470K/2200pf here. Same noise
.68uf piggybacking 820R to V2 pin3 (this was a .22uf with the JEL mod)
330pf piggybacking 100K to V2 pin6
What I had from JEL mod and still have
.0022uf coupling cap to V1 pin 6 (replaced .022uf)
.68uf/2.7K (replacing cold clipper to V1 pin3)
470pf piggybacking 100K to V2 pin8
Neg feedback: 100K to 47K on board >> 220k/4n7 >> 4ohm tap
Jake E Lee
https://drive.google.com/drive/folders/ ... ek5m96uNtV
#34
https://drive.google.com/drive/folders/ ... w_5hpSBlK1
I'm not totally surprised given the changes I made, but I took good care with the lead dress and used shielded wire where called for. Could it be a tube issue and the new mods are just exposing them? I'm testing it with the chassis back in the headshell, which has shielding tape on the bottom. Any suggestions are most welcome!
As a bonus, which can I try for more mid to upper mid punch? I'm happy with the low end and there are more highs than I need. I'm missing (for my taste) that punchy, solid kerrang right down the middle. The amp as a whole has punch, but not exactly in the frequency range where I would prefer it to be. I'm not sure what component(s) to manipulate for this.