[sdiy] sources of hum and hiss in a solid state guitar amp (LM1875) (slightly OT)

[anthony]

I should add that the PCB was really a basket case when I fixed it. If it 
weren't for the reverb or the tweed I would have taken it back to the pawn 
shop. I mean the force that broke the PCB also broke the pot that I had to 
replace. It looked like there was some water damage too. Actually it looked 
like it fell out of a truck into a ditch and they didn't find it 'til a week 
after they lost it. (But because of the tweed it still looks rad.) I pride 
myself in being able to breathe life into hopeless cases. I mean you should 
have seen the Hotfoot when I found it in my basement.

I am fixing this amp to a useable level, but I think I'm more and more 
leaning towards ultimately putting a single-ended tube amp inside. I'd love 
to put in a push-pull with reverb, but I don't want to have to cram a lot of 
wiring into a small space like that. Add to that the fact that I'd rather 
have a 12" speaker in this sort of combo... Well anyway...

Here's a twist: it might be too much trouble to bother doing for a small 
guitar amp, but I have some 2SA1265's and some 2SC3182's that I got out of 
an Alpine V12 car audio amp. I think I should be able to get about 70 watts 
from a comp pair. Hee hee! No no I have those eramarked for a big PA amp 
with a tube preamp using 12AU7's (did I mention that I have a number of 
sweet RCA side-getters? I'm sure I have before...). Actually at one time I 
had thought of using EL84's as drivers in this amp. Does that sound cool or 
just stupid?

Also I love it when people remind me to use my scope. I don't know what it 
is - it seems to be a thing with many people who have scopes they just don't 
think to use them - sometimes at a time when a scope is really the only 
thing that would work. And mine is right on my bench, right here next to my 
PC. I'm twisting knobs right now even...

Hey what does "CHOP" do? There's no "PUREE" or anything...