Replace Caps?

Depends.

Power supply caps tend to be pretty limited. Signal caps might, especially input/output coupling caps.

Best,
E

I've been looking for a "bug" in my system...a kind of resonance sound - like something loose and vibrating in the speakers themselves - a "fuzz".  I removed the tweeters which were sent back from the manufacturer as being fine...removed the mids - same story....removed the crossover - same story.  I noticed that the sound gets worse after a couple of minutes of playing....so - out went my 130 lb. amp.  The manufacturer says everything specs out ok, but would recommend changing the caps (2) - fine .....we'll take a listen upon its return.  I've been chasing this thing for over a year.

String - you might check a couple of things like cones on speakers tight against washers, check also for resonance in room furniture, tables, art on wall ( ask me how I know ! Ugh ), also use your vandertones to see if it is isolated to sub
put heavy weight on external filters, try sweep tone disc to try and isolate ( Cardas)
... bummer
hope amp solves it... did they replace power supply caps ? When those are weak but not toast they can sound like woofer bottoming but normally also accompanied by a raise in 60 HZ noise
you might also pop rail fuses...

What you describe sounds like an oscillation in the audio chain, preamp or amp. Could be caused by cables/interconnects, maybe? But that aside, the only “sound signature” I’ve heard as an indication of marginal/old capacitors was in my old Adcom 555ii where I could hear a slight “farting” sound when the unit was powered off and an slightly degraded bass response.

P.S. I assume it’s an SS amp given the weight but microphonic power tubes “can” also give the “fuzz” sound sensation, based on my limited experience.