As Tim described, you can do switching starting at either the front end and working down the line, or the other way (from speaker back to source). This will allow you to isolate the source of the problem (assuming it is in the component stream and not the room or your own ears). This switching also involves moving tubes from one side to the other to determine if the weakness is in one pair of tubes.
Right now, I have a substantial imbalance that I've isolated to my linestage, and it is not the tubes. Because I don't have any other obvious problem with the sound, I have been utilizing the balance control to compensate. At some point I will bother to have this looked into by someone more competent than myself.
I think balance control is an essential feature. There is always some some imbalance, particularly with phono cartridges. It is amazing how small an imbalance is actually audible. When I had a Levinson No. 32 linestage in my system, I could change volume and balance by as small an increment as .1 db. While a whole db of volume change when playing music is not reliably audible, a change of as little as .2 db in channel balance IS audible. That is why I had the builder of my tube linestage include balance control (I also insisted on remote volume control, something he was not normally inclined to include in his designs).
Right now, I have a substantial imbalance that I've isolated to my linestage, and it is not the tubes. Because I don't have any other obvious problem with the sound, I have been utilizing the balance control to compensate. At some point I will bother to have this looked into by someone more competent than myself.
I think balance control is an essential feature. There is always some some imbalance, particularly with phono cartridges. It is amazing how small an imbalance is actually audible. When I had a Levinson No. 32 linestage in my system, I could change volume and balance by as small an increment as .1 db. While a whole db of volume change when playing music is not reliably audible, a change of as little as .2 db in channel balance IS audible. That is why I had the builder of my tube linestage include balance control (I also insisted on remote volume control, something he was not normally inclined to include in his designs).