The dreaded SM900 60 cycle hum...

[carvinbassplyr]

So I've been playing some gigs where it was necessary to fill out my bottom end more and I've noticed that as I dial in more low end my amp begins to hum quite noticeably and it's even worse through the FOH because of the subs. I've tried googling any fixes but have found none. Does anyone know where to even start trying to remedy this? With all EQ knobs flat there is a hum present but it's so subtle that it just sounds like inherent amp noise. The moment you start turning up any low end however, it's sounds like a constant open A being played. It's not noticeable when I'm playing, but the moment the band stops or there's a passage where I'm not playing you can hear it and it irritates the FOH engineers. Anyone have any clue about anything that can be done to fix this? I know that these amps are known for this, but someone must know how to remedy it?!

[RickenBoogie]

Yes, a good amp technician could help. It's a good idea to have one nearby anyway, now's a good opportunity to find one and get to know him.

[username1]

I would try swap out the tube before taking it in.

[carvinbassplyr]

I've got a PHENOMENAL tech, but I just wanted to know if there were any suggestions to point him in the right direction to expedite the process. I already swapped the tube and it helped but did not cure the problem.