Output Tube Bias Adjustment Procedure
1) Warm up amplifier for 15 minutes (or more).
2) Turn off any equipment connected to the amplifier inputs and ensure that the Bias Display On/Off
switch is ON.
3) Using the adjustment tool provided with the amplifier, adjust each 25-turn trimmer potentiometer
to a point where its lamp does not glow. (This point should be midway between red and green.)
Counter-clockwise rotation turns the bias down, “towards green”.
Clockwise rotation turns the bias up, “towards red”.
Notes: If the lamp is glowing red it means that the bias is set too high. Do not turn the adjustment
potentiometer further clockwise as this makes the bias setting even higher.
If an output tube bias indicator lamp cannot be adjusted for both green and red, the associated
output tube is probably faulty.
Adjusting the potentiometer for one lamp can seem to affect the lamps of the other tubes as well.
This is normal. Allow each change to settle for a second or two before going on to the next
trimmer potentiometer. Repeat the adjustments as necessary.
Bias adjustments will be needed less often as the output tubes age.
Bias adjustments can be made at any time while using the amplifier - as long as the amplifier is
warmed up.
If the Bias Display On/Off switch is left on, one can easily check the bias settings at a glance.
This could be whenever the amp is not receiving input signals (such as during the blank time
between tracks on a CD or record).
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