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.