"I am now pretty certain that it is indeed a volume issue."
You may be correct but your experiment is flawed.
Most volume controls (potentiometers) have poor channel balance at very low volumes, but have a perfectly acceptable channel balance in the normal listening range. Just because channels are out of balance at low volumes does not mean that they will be out of balance at higher volumes.
Did you try any of the other suggestions ?
You may be correct but your experiment is flawed.
Most volume controls (potentiometers) have poor channel balance at very low volumes, but have a perfectly acceptable channel balance in the normal listening range. Just because channels are out of balance at low volumes does not mean that they will be out of balance at higher volumes.
Did you try any of the other suggestions ?