[WireNut]

 My preamp is a Sonic Frontiers SFL-2 with 8 6DJ8 tubes. I was told by Chris Johnson that if I’m using all unbalanced ins/outs that the trim pots/CMRR does not need adjusting. However, he said if I’m using unbalanced sources with the balanced outputs the trim pots/CMRR needs to be adjusted. What he didn’t explain is why and what’s going on.

 I tried the balanced outputs once with unbalanced inputs and the right channel was weak. Could have been the different interconnects I was using, I’m not sure. I went back to all unbalanced input/output connections and everything is fine.

What is going on when the trims pots/CMRR is being adjusted and why does balanced mode require adjustments and unbalanced mode does not?

[FullRangeMan]

My 2 cents are:
Commom noise rejection have all to do with 3 pins balanced inputs(grounded).

Of course unbalanced RCA inputs dont need apply pot regulation as it dont use a ground wire.

Iam not a tech guy, this important subject deserve a detailed tech explanation I can not offer.

[WireNut]

This might be helpful to a lot of folks. Any other thoughts on why cmrr / preamp trim pots need to be adjusted in balanced mode and not unbalanced mode?