Tubes Asylum

Tube bias tool

66.74.51.167

ppopp

I have two pairs of tubes which when installed, cause my tube DAC to sonically pull to one side (either way depending on which way round they are installed. A third pair I have are much more centered. All three pairs have less than 20 hours on them.

Is the the off-center issue something which can be corrected with tube biasing (if so, who makes a good tube-biasing tool)? Or did I just get two duff pairs?

Follow Ups:

RE: Tube bias tool - 6bq5 16:14:52 02/19/24 (0)
assuming the tubes in question are 9 pin medium to high mu dual triodes, you probably have tubes with very disparate gain.
Bias can help - up to a point - it is in the actual manufacture of the tube and the microdifferences -
Happy Listening
RE: Tube bias tool - Spantou 12:09:22 02/15/24 (0)
More information would help get you better advice. What DAC, do you have a schematic, what tubes, what do you mean with sonically pull to one side, is "pull" static or does it changes with volume?
My guess is that each tube serves one channel and that the tube pairs are poorly matched in gain, which causes one channel to sound louder than the other. Typically DAC circuits do not allow bias adjustments of tubes. You could try to match the lower amplification tubes into a pair, and likewise with the higher gain pair.
Good luck.

Edits: 02/15/24

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