Tube Biasing - CANARY AUDIO CA-303 Owner's Manual

TUBE BIASING

Bias voltage applied to the grids of the power tubes in the output stage should be
checked from time to time to keep these tubes operation at the optimum
operating point. A properly biased power tube will have a longer life.
To check and adjust the bias voltage of the 300B tubes, simply follow the
following procedures.
Tools Required:
Digital Multimeter
Long-handled slotted screwdriver
Procedures:
1. Making sure that the power switch is in the OFF position.
2. Install all the tubes to the corresponding sockets using a gentle rocking
motion. (See "Installing the Tubes" section for detail information on installing
the tubes.)
3. Connect your speaker leads, input cable and power cord to each amplifier.
4. Turn ON the amplifier.
5. Turn on the multimeter. Select the section for measuring up to DC 20V.
Attach and secure the negative test lead to the chassis or to the binding post.
6. Insert the positive test lead into the bias test point marked as "300B - 1".
7. Carefully insert a long-handled slotted screwdriver into the bias adjustment
pot marked as 300B - 1. Slowly rotate the screwdriver to adjust the bias
voltage until it reaches 0.55V.
8. Repeat steps 6 and 7 to adjust the bias voltage for the other 300B tube using
bias test point marked as "300B - 2" and bias adjustment pot marked as
"300B - 2". You will need to go back and forth a few times until both of the
300B tubes are properly biased.
9. Once you have finished biasing the two 300B tubes, wait a few minutes and
recheck the settings again.
10. Repeat these procedures to adjust the bias voltage for the 300B tubes on the
other channel of the amplifier.
11. The CA-303 Signature Edition mono blocks power amplifier is now ready to
use.