Bright channel noise

[cobretti]

On my 50W Marshall clone amp, the normal channel is perfectly silent (no hum, no noise) the other channel, bright channel, does introduce a lot of sssssshhhhhhhhhh noise even without anything plugged into it. The normal channel is I believe with 820ohm cathode resistor and 330uF cap. The bright one is with 2k7 cathode resistor and 680nF cap.

What the heck is going on? Where is the noise coming from? Is it the 500pF cap across the volume pot after the first 12AX7 that makes that noise?

 

[Michael Bean]

Not enough info...has it always been like that or was it a sudden change? The bright input channel generally has a high-mid boost, so some extra hash noise wouldn't be out of line.

Mike

 

[JMFahey]

Try plugging another 12AX7 there, you might have an old worn gassy one there, also replace the plate resistor.

I see no other possible sources of hisssss

 

[cobretti]

It's more like an amplified white noise I would say. It was like that since day one. More volume(gain) more hiss. I can hear it on some youtube videos as well. All tubes are new, resistors as well. I think it is more a design issue rather than faulty parts/tubes.