You have to adjust left and right 845 tube bias levels in each Amplifier separately.
Measurement is done via a multimeter at 20V DC setting. Insert black (-) probe into
black socket and red (+) probe into the appropriate (left or right) red socket. You
should read a value about 15V for each tube. If the readings are different, then
adjust the bias level via potentiometers near the 6SN7GTB tubes. A small flat
screwdriver will be necessary to access internal bias trim pots.
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ABSOLARE SET Amplifier User Manual 1.2