Hello all, I'm trying to eliminate noise for my amp setup. I'm using a Ceriatone OTS 50w & a small Epiphone 1x12 cabinet. I'll try to describe the noise I'm getting as well as possible. I've just recently had replaced both pre and power amp tubes. (I haven't baised the amp).

1. When the amp is connected to the speakers without input signal, its dead quiet. When turning Preamp Vol. past 12 o'clock I started to hear scratchy noise ard 600-800k.

2. When amp input is connected with a cable (not connected to any instruments), slight hiss sound appears(ard 10dba loud), noise disappears after turning both preamp and master vol. to 0 (either or).

Can any of you geniuses tell me where that "hiss" is coming from? Does it have to do with the amp? Preamp or power amp. I mentioned earlier I didn't bias my amp after replacing new tubes, could this be the effect?

Any help would be appreciated!