Bias adjustments
Left bias adjustment: Controls the bias of the two left-most output tubes, V1 and V2 (See
tube chart on pg. 12). The setting is locked in place by the outer locking nut. To make an
adjustment, slightly loosen the outer locking nut.
Right bias adjustment: Controls the bias of the two right-most output tubes, V3 and V4 (See
tube chart on pg. 12). The setting is locked in place by the outer locking nut. To make an
adjustment, slightly loosen the outer locking nut.
Note: The 4 output tubes work in pairs; the left bias control adjust the bias voltage for V1 and V2,
while the right control adjusts the bias voltage for V3 and V4. While the output tubes can only be
adjusted in pairs, a test jack is provided for each individual tube to provide more accurate bias
monitoring (e.g. trying to find a faulty tube).
Test jacks: For use with standard multimeter probes.
Black common probe jack: Plug in common meter probe here.
V1 red probe jack: Plug in probe to monitor V1 (See Tube Chart on pg. 12) output tube bias
voltage.
V2 red probe jack: Plug in probe to monitor V2 (See Tube Chart on pg. 12) output tube bias
voltage.
V3 red probe jack: Plug in probe to monitor V3 (See Tube Chart on pg. 12) output tube bias
voltage.
V4 red probe jack: Plug in probe to monitor V4 (See Tube Chart on pg. 12) output tube bias
voltage.
Bias procedure
WARNING!: Maladjustment of the bias controls can lead to output tube failure. The bias
adjustments are not fool-proof, and output tubes can be under-biased because a
reasonable bias range needs to be given to account for different output tube samples. If
under-biased for a sustained period output tubes will likely fail. Science Amplification is
not responsible for output tube failure due to mal-adjustment of bias controls.
Please familiarize yourself with the bias procedure before making bias adjustments. If
you at all feel uncomfortable making adjustments, take the amp to a qualified technician.
We do, however, encourage you to bias yourself because it is completely safe. It is also
easy once you get the hang of it, and can save you quite a bit of cash!
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