Experiencing speaker imbalance, while amp headphone output is fine. Any ideas?

Big laugh @ pepper spray. HA.

So, I have done the unplugging/replugging and checked all controls.

Now, just tried swapping channels. Sent the perceived hotter L output to the R speaker, and the R output to L speaker. As expected, now the R speaker is the louder one. It's a difference of 10db at my usual listening level. Crazy. 

Next thing to try, I guess, is musical chairs with the tubes. I'm bummed though as these are brand new tubes.

I'm bummed though as these are brand new tubes.

It sounds like you burned in the tubes and found a dud.

Not familiar with that particular ARC amp, if it is new from a dealer then you can get a warranty replacement tube from ARC, assuming it is a tube issue. If you discover it is a tube, call ARC they will send you out a new one. Maybe even a new full set.

It sounds like you burned in the tubes and found a dud.

Thanks. I hoped that ARC's factory burn-in test would have ID'd the bad apples before shipping, but I won't be too unhappy if the issue is as simple as a bad tube.

if it is new from a dealer then you can get a warranty replacement tube from ARC, assuming it is a tube issue. If you discover it is a tube, call ARC they will send you out a new one. Maybe even a new full set.

Yep, brand new. Thank you for this info. Will lug it to my dealer to suss out asap.

OP did you keep the old tubes? Usually 24-48 hours after they have been moved or shipped. That is usually the deal. So they get burned in and then they are shipped and placed in service. Usually after 48 hours they are ready for normal service. Shipping and moving is a valve killer..

Take a pencil and tap the tubes with the volume down.. You might be surprised.

R&R the new one with an old one UNTILL you  get the new valve. Or XChange the set.. 5 minutes I'm up and running with my amps. Mac, Cary, VTL, DIY

Regards