Genz Benz Shuttle 3.0 amp soft distortion

I very recently acquired a used Genz Benz Shuttle 3.0, made around 2007, and discovered that it has a problem. Paging @agedhorse for his insights.

A bass signal reaching the speaker out and headphones distorts slightly, with the distortion especially audible as a tone decays. The noise presents as a kind of kizz-z-z-z-z-zyip accompanying a bass guitar note as it naturally swells then decays, just up until the front panel signal LED goes out. The fizzing ends every time in sync with the signal LED going out.

I've determined that the distortion is not present in the shuttle's send or post eq DI. For example, if I run a source into the front of the shuttle and send or DI that signal to another device, the signal arrives there free of any issues.

I can return a signal to the 3.0 return from a known good amp send and will hear the issue in the shuttle's speaker out and headphone outs. I imagine that definitively rules out the shuttle's pre-amp section as the source of this issue. The issue is present when using the Aux in as well.

Does this sound like a repairable problem? Am I dealing with an amp having a failing power section? Could it be an issue with the 3.0's built in limiter (though I'm not inducing clipping)? Could I simply have a dirty interconnect within the amp? Thanks for any and all assistance !

 

PM sent.

 

Follow-up... Thanks agedhorse for an outstanding, professional, and reasonably priced repair job! My Shuttle 3.0 is back in action.