Tube amp bias adjustment advice

@mmporsche The first step is to swap the interconnect cables left for right at the inputs to the amplifiers so that you can determine if the amps are at fault. It could be something upstream.

If the problem stays put => amplifier problem
If the problem moves => problem upstream
If the problem stays put, swap the input tubes, not the power tubes. In this way no bias readjustment is needed. Most of the gain in the amp occurs in the input tubes so this is the most likely area to have a gain issue!

The bias will not affect the gain unless its a mile off! It affects *distortion* and usually at higher power levels.


Keep us informed of your progress.

"This is a second set of tubes, had the same issue previously so I am thinking it may be room acoustics. "
Had the same problem with center image staying in the center until I did room treatment. Problem solved.

You should also move the speakers left to right to see if the issue moves with the speakers. That'll eliminate the speakers as culprits. Simple enough.

1. at least it is a constant rather than a damnable intermittent problem.

2. when did this start? was it balanced before with a prior amp? With this amp before you changed the bias? this amp before you changed the tubes? did you move your speakers in/out of position? speaker wire connections checked?

3. anything else changed prior to the amp/tube/bias change? IOW, if nothing else was changed, then no need to suspect other equipment in the chain prior to amp and speakers.

4. but, even if not changed, a cable could have been inadvertently disrupted. my most recent imbalance turned out to be a cable, a very good cable, but became slightly loose on the rca input. Squeezed tight with pliers, problem gone, then replaced that pair with tight ones.

5. did you change which inputs you used on a preamp or integrated amp? gotta think that thru.

........................................

a. swap all left tubes with right tubes: problem still on left? not the tubes.
b. change speaker wires on amp, problem moves to the right, or still on the left? 
c. without changing anything else, move the speakers themselves. problem still on the left? good, speakers are fine!
d. put the speaker wires back correctly l/r on the amp.
e. narrowed down to ___ possibilities?
 

Room acoustics can be a bear to deal with, especially so when the room has to serve other family uses, or, for example, meet the decorating needs of a spouse. That said, small changes in speaker position and adjusting things like toe-in can often have a dramatic effect even if you can't add much in the way of wall treatments or the like.