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I need help setting bias

I'm having a problem trying to set the bias on an Audio Research CA50 integrated. The optimal setting is 65ma, but the highest setting I can get using the bias adjustment is 50-52. The output tubes are 6550, and the input and drivers are 6922. I swapped the 6550's for newer ones but it made no difference. What would be the reasons for not getting a higher bias setting? Thanks in advance
audiojerry
detlof
1,899 posts
 
I'd check the driver tubes for good measure.
audiojerry OP
78 posts
 
Thanks Detlof, I didn't think the driver tubes could affect an output tubes bias. I can't check the driver tubes, but I can replace them with spares.
detlof
1,899 posts
 
Audiojerry, I am not sure, not knowing your configuration, but I had a similar case years ago with an ARC D-79 and checking the driver tubes solved the problem if I recall right.
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