Tube amp bias adjustment advice

The balance control of many otherwise fine preamps and integrated amps have disappeared over the years. It is simply a cost cutting move as there is no reason that a balance control has to compromise SQ. I would not have a preamp without one.

There are many reasons a balance control may be useful as were detailed here.  An additional factor is that some recordings need a balance control to place the soundstage correctly.

IF you do testing be sure to use a tone generator so the exact same level and tone go to each speaker. That should tell you if there really is a difference in gain between the two channels. Then you need to take the necessary steps to isolate where the gain difference is located, it may be a cable, in the preamp, or as you originally suspected in the power amp. But doing an overall gain measurement at like 1 khz one foot from the speaker with a sound level meter at each speaker will tell you beyond any doubt if there is a level difference.

Could just be room acoustics and moving speaker few inches closer than right.

Could be your hearing also at times ...I have tinnitus and some days my hearing is not as clear as others ..With my Raven tube Reflection I have been thinking of putting a balance control on it for that reason on days I just feel off..

But I find I am moving more to left side to make up for the lack of control of balance ..My living room will not allow me to keep the speaker 3 inches I need out and moving 80 lbs each time is not best condition..

And to be honest it could be just the way it was recorded in some songs.. I have found some recordings are not total balanced and hear another song and the left sounds louder than right...

Could be few things going on ..