Threshold SA/2 Amps One running hotter than other

I just purchased a pair of Threshold SA/2 optical bias amplifiers in their original unrestored state. They sound amazing with no noticeable issues. However, I have noticed one amp runs about 7 degrees warmer than the other(100F vs 107F)at the same midpoint on the heatsinks. Regardless of input or speaker swapping L for R channel it is always 7 degrees warmer. Should I be concerned or is this likely a bias issue I could address myself as an amateur? Or is this within a normal range of difference between amps?

Thank you

Joined 2015
Paid Member
Welcome to diyAudio.

Recommended temp for optical SA/2 is 42C (107F) so one of them is spot on.
The difference is nothing to worry about, but it is possible to adjust. There is an official bias procedure available.
If you choose to do it, please be very VERY careful. Old trimmers might not react the way you expect them to.

(This should really be located in the Pass Labs forum)