Heard it today for the first time, with the amp idle for more than 15-20 minutes. The popping sound comes out at a 2-3bpm rate, but here's the catch: only on high, if the Output switch is set on standby or low the noise disappears. The noise level doesn't depend on the master or channel volume level, gain level or whether there's a guitar plugged in or not. Should I get one preamp and one power tube and start swapping tubes? Or maybe a dodgy solder joint? Other ideas? Thanks in advance.
IME this type of thing is usually associated with tubes, and from what you describe, I would start with testing the preamp tubes. Recently I've noticed that current production Russian made preamp tubes can be pretty noisy even when new (TS and EH). If you have say two of these in your amp, you may need to swap both out and replace with Chinese tubes during testing. This is exactly what happened to me last year, only it affected both channels since I had Tung Sols in both V1 and V2, and it was hard to troubleshoot because I was only using one replacement tube at first. I ended up leaving the TS's in there because they were new, had great tone, and they stopped being noisy after about 25 hrs of use.
Thank you both for chipping in, really appreciate. Have it running today for about 30mins or so on high output and it's dead quiet, no popping yet. See if I can replicate it and will check the tubes for any flashing lights. Cheers.
