“Center” of soundstage is left of center…

I’m reversing the power amp inputs now. I played some cds and the problem was still there so the phone pre doesn’t seem to be the issue. If the proble migrates to the right side after I’ve reversed the power amp inputs then it must be the pre(?).

OP:

Yes. If the problem persists after swapping inputs, the next thing to do is swap amp outputs. If the problem persists then it’s either the speakers, the room or your hearing. :)

I have this exact problem and tried many times to locate the source. After a few years I found out (hearing test) that I have a significant hearing loss in my right ear. It’s a fairly narrow bandwidth, but I barely hear anything in that band. It’s the root of my tinnitus. Music that’s engineered with instruments panned wide left/right is fine, but anything subtle has a distinct left of center image. 

Lots of good comments. Could also be one speaker is slight forward of the other

Did this just happen one day when the previous day it was centered?