Marshall 2203X hum/buzz

Miro9486

New member
Hi,
I just got brand new Marahall 2203X fresh from retailer. It’s got some buzzing/hum problem. It’s not really present with nothing at input, much less audible in low input, more present in high one. Rising with higher master volume and gain. Persisting with different guitars and cables. Doesn’t seem to interfere with playing, also with guitar vol rolled back. I’m just wondering if it’s more of „physiological” hum of hard pushed amp (gain at 10) with steep curve of MV(getting loud really quick), maybe some ground loop/dirty power, sth else? Just looking for some quick troubleshooting. Haven’t changed speaker or spkr cable, havan’t changed socket/power source yet.

https://youtu.be/bcep81e6ERM

Some vid
 
It's common for these to be kind of buzzy but usually fore when using an overdrive or gain/pedal. There is actually a hum balancer on these, it's next to the bias trim pot, i learned that the hard way, lol.
 
could be a shitty tube in the V1 spot. A lot of new 12ax7s are too noisy for this spot. But I haven't looked at a schematic of this amp to know if it has AC or DC to the heaters. If it has DC heaters, then the hum probably isn't due to a crappy V1 tube...
 
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