Speaker balance control

After 50 plus years and regardless of the amount of time, effort and money spent, I have finally ended up with the best sounding system I've ever been able to achieve. This combo of components was a matter of luck more than informed design but, be that as it may, I'm very happy with it and not likely to change anything at this point. The setup consists of Shanling S100 CD, Peachtree Nova as a preamp, Peachtree 220 amp and Martin Logan Odyssey speakers that I've had since new in 2003.

However, there is no balance control capability in the preamp and I'm battling with an issue of uneven volume between the two speakers. I realize that the speakers I have are very dependent on placement, rake and toe in, which I'm assuming may be related to the curvilinear transducers and the nature of dipole speakers in general. I've spent a lot of effort experimenting with this aspect of adjustment.

That being the case I still have been unable to achieve a volume balance between the two. I've switched the speakers left to right and right to left and have done the same with interconnects from the CD player and even switched speaker cables with no change; the sound balance perception remains significantly in favor of the right speaker.

What convinced me that the problem was not in the sound stream of the system occurred when I stood at my seating position with my back to the speakers and heard the sound still predominantly from the right. Others that I've had listen from my chair say the sound level seems balanced so it boils down to a deficit in my perception.

I'm getting up in years and have experienced some hearing loss, mostly diminishing above 5000Hz, and was fitted with hearing aids just to try solving this problem. This helps but I just can't get used to the unnatural listening associated with their use and haven't used them for any purpose for over a year.

Ok, I'm finally going to get to the point of this thread. Without a balance controller on my preamp, is there a way of attenuating the right side speaker volume to accommodate my hearing issue? I've even thought of installing a variable resistance device either as a line level controller between the CD player and the preamp or in the speaker wires themselves.

Otherwise, I can close my eyes and pretend that center stage is on the right side of my room.