If you have systematically switched the L and R channels starting at the source and ending up at the amps end and notice no change in the off centre balance, then you can rule out the equipment. The only thing left to do is switch the speakers from L to R to determine if for some reason one speaker plays louder than the other. If the off centre balance does not shift, it is simply your room, and that is why we have balance controls.
Do I have a "balance" problem?
My system is in a dedicated room, 13 x 12.5 x 8.5, with one chair centered between the speakers. The speakers are several feet away from the front and side walls. I've treated the room, including absorption panels to deal with first reflections. Here's my issue: to get proper L/R imaging, I have to set the balance control in favor of the right channel somewhere between (depending on the recording) 1:00 and 2:30 on the dial. My system has always been this way and the issue is consistent with both LP and CD playback. I recently auditioned three line stages and each one required the balance control set to the right. By way of "troubleshooting," I've switched tubes, cleaned all contacts, and systematically switched L/R cables on each pair of interconnects one at a time. Nothing changes. There is no degradation of sound in the right channel (at least to my ears) and when the balance is set properly the music sounds great. But I just don't understand why the balance control needs to be set so far to the right. Does anyone else out there have a similar situation? Is there something "wrong" with my system? Thanks in advance for your thoughts.