Currently Being ModeratedJan 20, 2013 9:26 PM (in response to DarKstar7762)Re: Amp Making crazy feedback noises with all knobs turned to zero
Have you tried plugging a lead into the effect return (with nothing plugged into the other end of the lead). This would isolate the digital preamp from the tube power amp section. If the noise is still there, it proves the fault into the power amp which could possibly mean a faulty output, driver or phase inverter tube. You would have to swap out the tubes to see if that is the problem and I would try the 12AX7 tubes first (driver and phase inverter) then the output tubes. If you know someone with a tube tester, that could also be an option.
If all the tubes seem OK, then the only option your left with is to get the amp to a repair shop. Alternatively, if plugging in the lead into the effects return jack causes the noise to disappear, then you've got an issue with the preamp which means a trip to a Line 6 service centre.
I would also try plugging an XLR lead into the DI output on the back of the amp out and monitoring it in a mixer or some other audio device as the XLR output is always active regardless of the standby switch status. If you're still getting the noise from the DI out when the standby switch is off then the preamp is definately the culprit. Plugging in a 1/4 inch lead from the "Preamp Out" to a mixer would also do the same thing. Just ensure the standby switch is off when you try either of these.
Currently Being ModeratedJan 31, 2013 7:26 PM (in response to DarKstar7762)Re: Amp Making crazy feedback noises with all knobs turned to zero
Replaced the 12ax7 tubes, there was no feedback when i listend through the direct out and into a mixer. Now that it has new tubes it sounds ok for a second then the noise starts again