Hi all!
So, I’ve got it... & quite naturally—I’ve (already) got a question. Now, I’ve had a lot of tube amps over the years, yet I know almost nothing of their maintenance. I’ve never even retubed an amp, outside of an initial pro jr that came in “near mint” cond. but sounded like it was possessed form the moment you turned it on. Once the shop took care of that (new tubes), it worked fine: actually, it took two attempts as the first set they slapped up in there made the problem somehow even worse! My local shop did the repair; I’d ordered it from another across the county...
I either, have never played them hard enough (most were either purchased new or in very great shape), or sold them beforw needing such things. Most recently, I had a Mesa combo & as I understand it, you don’t even need to rebias those, so long as you use their brand—&id has that one fro about 5 1/2 hrs (I guess I did replace the power tubes once, just to see what would happen - Id been given a free set with a prior purchase that turned out to be a defective amp/& though a different model, they were the same tubes, and seemed to function fine or the same once this was done).
Now onto — finally — my most recent acquisition: it is a 15 yr old hybrid Marshall (which I believe means that the preamp, or possibly distortion/od channel is tube). So, when you turn it on, it makes a continuous noise. That were I turning the volume up loud enough, or not using any reverb at all, or playing only on the clean channel (solid state, I think), it would be very minimal, if not go all the way away. What I am wondering is, will changing the preamp tube eliminate this annoying noise which is so nuisance inducing, at least to my overly sensitive ear, that I cannot think when playing (outside of it: the buzz). It is there when turned on. It stays there when played. It gets better if you dial the reverb back all the way off / to zero. If you disengage th e od (overdrive channel), it gets better, too. I’d almost say that each of these two things comprise about 50% (apx.) of the noise. If however you put it on the clean channel and turn both volume & gain dials (what this amp labels “pre-amp), up close to noon, you will still hear it some. This is one of those valvestate 200 avt models. I had one when new, but that was so long ago I don’t know if this was present then. And it might i to have bothered me that much when I was younger, and likely to be playing at much louder than middle of the night, bed/living room volumes. It kind of sounds like if you see footage of an old fender amp that’s dimed on stage—& they go to switch it on : that hum or whatever you want to call it, or similar to a fender Mexican strat with the single coils activated exclusively on certain amps (positions 1, 3, & 5?)...
I don’t know, maybe it’s normal. Shops bit responding to inquiries; but I guess that’s to be expected given the current climate and conditions. I’ve had two or three jcm 2000 dsl 401’s (none of the ones that melted from the tubes!); all used come to think of it... & none of them encountered such a thing. I don’t know anything about scratchy pots , or anything, or even if this has those!
Sorry for the novel, and thanks if you’ve got any ideas.
