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Hello,
Lately I have been trying to get clear about what causes a strange form of distortion to my signal in the normal (clean:ish) channel on my JCA50H amp. I started noticing it when I began playing an SG with humbuckers more frequently through it. (For a while I played only low-output single-coils, with which the problem is much less noticeable.)
What I noticed was a subtle distorted sound in the background, which I felt was not the preamp tubes breaking up, but which appeared to be more or less constant over the range of the preamp volume (gain) settings. Yesterday I noticed that if I turn the master volume up halfway or so, and the preamp volume down to zero, I still hear this distorted sound very clearly, though not very loudly. Or: I hear *only* this distorted sound. My guess is that as I then turn up the preamp volume, this distorted sound stays there.
You (or, at least, I) would expect that when you turn the preamp volume down to zero you would get zero signal, or a very very diminished signal. Instead, as I turn the volume down, I get less and less of my normal, clean sound, but this distorted sound is there all along and still there at zero. If I back off on the guitar volume, the noise goes away, of course.
The distorted signal sounds something like when you're playing through a tubescreamer maxed out hooked up to a cheap transistor radio instead of an amp. And at very low volume, but it's there.
I have checked the tubes for problems with microphonics, (tapping them w/ pencil) but there seems to be no trouble there. Maybe I should start swapping them around, though.
After a while, however, the noise sometimes goes away, which makes me think it has to do with insufficient warm-up somehow. But since in that case it seems the amp needs half an hour or so to warm up, is this normal?
Another wild theory I had (which is mere speculation since I don't know how to go about testing it) is that it has to do with grounding somehow. Or a faulty capacitor somewhere in the amp. Again: wild speculation based on ignorance and superstition. I am a novice in these matters.
Any help or pointers would be greatly appreciated!
Lately I have been trying to get clear about what causes a strange form of distortion to my signal in the normal (clean:ish) channel on my JCA50H amp. I started noticing it when I began playing an SG with humbuckers more frequently through it. (For a while I played only low-output single-coils, with which the problem is much less noticeable.)
What I noticed was a subtle distorted sound in the background, which I felt was not the preamp tubes breaking up, but which appeared to be more or less constant over the range of the preamp volume (gain) settings. Yesterday I noticed that if I turn the master volume up halfway or so, and the preamp volume down to zero, I still hear this distorted sound very clearly, though not very loudly. Or: I hear *only* this distorted sound. My guess is that as I then turn up the preamp volume, this distorted sound stays there.
You (or, at least, I) would expect that when you turn the preamp volume down to zero you would get zero signal, or a very very diminished signal. Instead, as I turn the volume down, I get less and less of my normal, clean sound, but this distorted sound is there all along and still there at zero. If I back off on the guitar volume, the noise goes away, of course.
The distorted signal sounds something like when you're playing through a tubescreamer maxed out hooked up to a cheap transistor radio instead of an amp. And at very low volume, but it's there.
I have checked the tubes for problems with microphonics, (tapping them w/ pencil) but there seems to be no trouble there. Maybe I should start swapping them around, though.
After a while, however, the noise sometimes goes away, which makes me think it has to do with insufficient warm-up somehow. But since in that case it seems the amp needs half an hour or so to warm up, is this normal?
Another wild theory I had (which is mere speculation since I don't know how to go about testing it) is that it has to do with grounding somehow. Or a faulty capacitor somewhere in the amp. Again: wild speculation based on ignorance and superstition. I am a novice in these matters.
Any help or pointers would be greatly appreciated!
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