IMAGE PROBLEMS VOCALS OFF CENTER

Shadorne wrote

"If you have swapped interconnects (between source and power amp) and you have (in a separate test) swapped speakers with their respective cables (left channel to right side and right channel to left side) then you have eliminated your system as the source of the problem."

So did you ever swap the speaker connections so that the left output of the amp is driving the right speaker and the right output of the amp is driving the left speaker ?
I didn't see an answer to this question, and in my opinion it is the key question.

Try what Seandtaylor recommends above. Then, also try forward toeing-in /very slightly/ your right speaker -- i.e. the speaker the vocals are closest to.

Swap the speakers. If it remains, it is not your speakers.

Completely swap the speaker cables:Disconnect completely and put the right cable on the left side (amp to speaker) and the left cable on the right side (amp to speaker). If it remains, it is not your speaker cables.

Now swap the speaker terminals at the amp. (use the right amp channel to drive the left speaker, and the left amp channel to drive the right speaker). What was being presented to the right side of your amp is now being presented to the left side, and vice versa.
If the sound DOES change (you hear a shift past correct to the right side) Your Amp is OK.

IF the sound does not change, (same left-prevalent image) Your amp, somehow, it to blame. Check Bias on the tubes. Swap JUST the power tubes.Listen. Then swap just the pre/driver/input tubes. Listen. IF the Amp is auto biased, the circuit could be pushing a power tube too hard because of a weak driver/input (Maybe, someone else chime in here).

Completely swap the right and left ICs between source and Amp. IF still there, not your ICS. Now swap the ICs at the rear of the source. IF it is still there, hire an exorcist.

By the way, I had a similar problem a while back. Hearing tested. Everything done. The only difference between my situation and yours is that no-one else heard my issue.

I would suggest that you get as many different opinions (without leading them to hear what you hear) by asking "is teh image center, right, or left"

My problem is that, while my hearing is fine, I am right eye-dominant, and tend to turn my head to the left while searching Visually for the center image in the soundstage.
Perhaps not coincidentally, my right ear is slightly farther from the tip of my nose (or the center of my face) than my left ear. SO, I have to turn my head slightly to the left to present my ears at the same plane. When I do this, I hear the image in the center, but my head is oriented slightly to the left. If I remain focused on the center point by gazing slightly right (so my head is turned slightly left, but my eyes are straight ahead) I hear ( and "See" which is just as important) the image as it should be.

Don't measure your head if you aren't prepared to see a couple millimeters of diference!!!

Like trouble shooting computer problems you're gonna need to eliminate one problem at a time.

If you are convinced the room is acoustically symetrical and your physical arrangement is good, and you've switched all cables and equipment including speakers back & forth with the same off-center effect, I think you're back to the room. There is something you're missing. (There is an old saying that when you hear hoof beats you look for horses before you look for zebras - unless you're in Africa.)

Would it be a dumb question to ask if you've taken an album where this effect is pronounced and listened critically to other systems outside your home? If you hear an off-center image there, it could be that you're experiencing a change in your hearing ability due to age, past hearing damage or another medical issue. Been to an audiologist lately? (I do recall you saying others have heard this, but never hurts to check with your doc.)

If it is external EFI that is causing the problem, it would presumably be picked up by the speaker cables since they are the only ones not physically together from source to amp (unless you have outputs to monoblocks by the speakers.) You could try doubling the length of the speaker cable and looping a section over to the other side and see if that causes a similar shift in image. (You might have to use cheap wire for this test to get the extra length.)

You could also check out alternate speaker cables. Some offer better shielding, akin to a coax or balanced cable type shield.

Or, you could move the equipment to the opposite end of the room and see what that does to your image. If that does change things, you could be back to re-examining your acoustics or possibly have revealed an EFI source that is stronger at the other end.