2. amps-preamps
  3. 1040920496

Correlation between tube bias and hiss?

I have a Dynaco ST-70 that has performed well but now has an occasional hiss in one channel that lasts a few seconds. I have switched preamps, cables and speakers and isolated it to the amp. I checked the bias on both channels, which is to be set to about 1.56V. However, neither channel, fully adjusted will go above about 1V. Is this a sign of bad tubes? Might the hiss be related to this?
albertk

Showing 1 response by sean

sean
6,231 posts
 
Sounds to me like you need tubes. Could be something else or a combination of problems, but a spare set of inexpensive tubes would be a good place to start. Just remember to check the bias on the tubes RIGHT AWAY after installing the new ones. Sean
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