13
4. It is important to note
the
V1, V2, V3, and V4 bias levels
are
increased
by
turning
the bias adjustment
screw
clockwise and the bias levels
are
decreased
by
turning
the bias adjustment screw
counter-
clockwise
.
Before you start. When you use the Exact Biasing system you will need the small screwdriver that came
with your unit.
Biasing Layout
Top panel
Exact Biasing:
A quick and easy method to bias the amplifier, to make certain the tube is at the right bias point or to re-bias.
For this type of biasing only a small plastic handled Tuning wand that comes with your unit is needed..
1. To start the process, turn the unit on with the volume knob turned to zero. No audio source should be
playing at this time.
2. Allow the unit to warm up for at least five minutes.
3. To check your bias, simply turn the bias selector switch to V1, V2, V3 or V4.
The meter reading for
EL34s/6CA7s is 40 milliamps plus or minus 4 milliamps. The meter reading for 6550 tubes is 50
milliamps plus or minus 5 milliamps.
If the reading falls within those parameters, adjusting the bias is not
necessary. Please note, that if you are reading the meter while music is playing, the reading will fluctuate.
4. To bias the V1 tube, set the Bias Selector switch to V1. Then take the tuning wand, and with the cupped end,
insert it into the V1 hole. Increase the milliamps by turning the screw clockwise and decrease the reading by
turning the screw counter-clockwise. Follow the same pattern to bias the V2, V3 and V4 tube. Please note that if
the meter reading fluctuates while music is playing, this is normal.
5. Rebias the tubes again after the initial first bias pass. The reason is that all the tubes use the same power
supply voltage. Increasing amperage to one tube will reduce the amperage from the other three tubes. In like
manner, decreasing the amperage from one tube will increase the amperage to the other three tubes.