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Manual Bias Setting Using a Multi Meter
- First, make sure no equipment such as headphones or other source device is plugged into the amplifier
- Turn the volume knob down counterclockwise (its lowest setting) and make sure the power is off
- Insert your tube of choice into the amplifier and make sure all proper jumper tabs have been placed according to your
tubes voltage and how you want to use the amplifier
- Set your Multi-Meter (DVOM or DMM) to voltage DC. Set the range for 20VDC. The Bias test points are large enough for
you to insert the probes of most DMM's directly into the board so you do not have to hold the probes up. Make sure no
metal parts of your probe touch any other components on the amplifier as a short could occur.
- Turn on the amplifier and watch the voltage for around 30 seconds. If the voltage does not appear on screen, turn each of
the blue 25 turn trimmers 10 turns counterclockwise then re-check.
If it measures under 20, let the amp warm up for 15 minutes
- Once the amp is warmed up, measure each of the two positive bias points in real time while turning the adjustment screws.
(Counterclockwise will lower voltage, clockwise will raise voltage) Dial in each side to around 22VDC
- Plug your music source into the RCA jacks on the back side of the amplifier. First, only use a cheap set of headphones to
test the sound of the amp in case of any assembly issues. Once you are satisfied the amp is functioning properly, plug in
your favorite headphones and enjoy the amp! Re-check the bias every 30 minutes for the first few hours and make any
tweaks as needed. Please remember to disconnect headphones, source devices and turn the volume its lowest settings
prior to tweaking bias
Once bias measures stable, every few months or longer depending on how much you listen to the amp, it may need
its bias calibrated again. This is normal. Also every time you make a change such as changing tubes or changing
input capacitor jumpers, you will need to re -calibrate the bias
22 VDC
22 VDC
ROTATE TRIMMER
CLOCKWISE TO RAISE
BIAS VOLTAGE
ROTATE TRIMMER
COUNTERCLOCKWISE TO
LOWER BIAS VOLTAGE
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