Or you could use an outboard digital EQ ie an Ultracurve and use it as a balance control. I have hearing loss in my left ear, and though I still cannot achieve an absolutely perfect center image like before, it is close with this set up. I have found that the Ultracurve is 100% transparent and quiet in my system.
Can I tweak L-R balance by differntial biasing?
My new (to me) Almarro integrated does not have a balance control but my room is slightly asymmetrical. I'm playing a little w speaker toe-in to try to correct this, but I just had another idea. Bias spec is 0.20 volts, with 0.18 volts suggested as a minimum which will reduce output slightly but provide more tube life. It seems to me that if I bias the output tube slightly lower on the "louder" side, it might shift the balance slightly toward the side that is biased higher. Does that make any sense???