摘抄一段，有理由相信av123 (onix) sp3就是melody sp3 （原文：
http://av123.com/manuals/sp3_bias_procedure.pdf）：
Below are instructions for biasing your SP3. It is not necessary for new owners
to bias their amp as this is done from the factory but it should be checked once
per year or any time you replace the tubes.
Biasing your SP3
Please look at either side of the SP3.
You will see 5 holes on each side.
You will find something like this:
/ 1.15V \/ 1.15V \
* * * * *
A B C D E
1) Perform these adjustments once the amp has been turned on for at least
one hour.
2) Use a volt meter set to DC to test between A & C. Please adjust B so that
the volt meter shows 1.15V.
3) Use a volt meter set to DC to test between C & E. Please adjust D so that
the volt meter shows 1.15V.
4) Repeat on the other side.
This assumes stock tubes. Aftermarket tubes may have different voltage
requirements.
Note that the pots are extremely sensitive. You may have to turn them quite a
bit to have any movement in voltage. This allows extremely precise
adjustments.
