CANARY AUDIO 300B Owner's Manual - Tube Biasing
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 20V DC.
6. Start from the 300B - V5, insert the positive test lead into the RED bias test
point and the negative test lead into the WHITE bias test point.
7. Carefully insert a long-handled slotted screwdriver into the bias adjustment
pot next to the 300B - V5 tube socket. 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 all remaining seven 300B
tubes in the same fashion as biasing 300B - V5. Using the bias test points
and bias adjustment pots next to the corresponding tube socket for measuring
and adjusting. You will need to go back and forth a few times until all eight
300B tubes are properly biased.
9. Once you have finished biasing all eight 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 Reference One mono blocks power amplifier is now ready to use.