Audible Illusions is based in Daytona, FL. and their tube preamps are well regarded. Also, their preamp has two "balance control" knobs (one for each channel), in addition to the master volume control.
The owners manual describes the balance controls as follows: "The amount of signal voltage applied to the line stage for each channel is regulated by separate stepped attenuator controls. The relative signal of the CHANNEL BALANCE is set with these controls. Setting both of these controls at 12 o'clock is a good starting point."