Eventually all tubes will wear out and my question is if there are any instructions available for biasing a pair of new 6L6? Mine are still fresh, but when they eventually wear out (or fail) I want to be prepared to be able to perform a quick swap to have the PS-2 up and running again as quickly as possible, because I kind of depend on it and I only own one.
Hi Carl,
No re-bias is needed. Any matched pair can be used with the PS-2A. So just make sure you have a back-up set of 6L6s and a 12AX7. Any brand of tubes is OK.
HI Dan,
Thanks for the response.
I was under the impression that the PS-2A had fixed bias and cathode bias and then different sets of 6L6:es will give different bias measurement in all other fixed bias guitar amps I have ever owned or used.
I’m not questioning what you are saying, but does the PS-2A have some sort of clever auto bias feature or is there another explanation to why one doesn’t need to set the bias when replacing the 6L6es?
With other fixed bias tube amps I know, too low bias will make the amp under perform, while too hot bias with shorten the tube’s life.
Thanks,
Hi Carl,
Yes, you’re right; it fixed bias. Typically we suggest just replacing it with any matched pair, and 100s of people do this without issue. Let me check on a few things and I’ll get back to you!
There is no re-biasing provision built into the power station. Of course it’s possible if you know what you are doing. But we don’t recommend end users do this; it is a professional service task. In almost all cases it is not needed anyway.
To add to this, Power Station is designed to accommodate most tube brands’ plate current ranges, so slight tweaks to plate current are not needed. If you tube are tested and matched, just get something in the middle of the range, not to high or low. etc.
Thanks.
I have been playing fixed bias tube guitar amps since I was 13 and the bias have always been checked and set when replacing power tubes, so I was surprised to hear that a premium amp manufacturer like Fryette is suggesting changing power tubes in a fixed bias design without checking and setting the bias.
But I trust you, I know a little bit about electronics and tube amps, but I am in no way an expert. But you are. 
Perhaps you are biasing your Power Stations very low to ensure that any matched pair will work without running too hot. That will of course make life easier for everyone, although it might be at the cost of slightly compromised performance.
Hopefully a local tech can work out how to bias my PS-2A when it’s time to replace the tubes. But it’s good to know that it will still work fine without checking and setting the bias as ling as the pair is matched.
Hey Carl,
I asked, Steve, and the above was his advice to you. I think it’s one of the considerations (and advantages) in the Power Station’s design. Fryette tube amps are typically rebiased, and we have biasing instructions for those.