DSL 100 "Swoosh" Sound

[Red Solo Cup]

I figure this is a power tube or dirty socket issue. There is a "swoosh" sound, kind of like waves, faintly in the background when the amp is off standby. Increasing the volume does not make it louder and turning gain up/down makes no difference. Also, I can hear it on either channel. I have extra tubes and will try to swap out later. The amp still sounds fine with no other issues noticed.

For now, what do you think? Just wanting to see what y'all think before I pull down my amp wall to investigate.

 

[Deadpan]

Yeah, most likely power tubes.