had a bias pot put in to be able to adjust the biasing, I went with 7581A tubes due to the headroom they are great tubes, have them in my ampeg PF-50 and my Ampeg V4B.Hey-ho, what did you change on the amp? And what was the reason for doing so?
Trying to get 6 tubes all matched has been a flat out PIA to get , taken 2 months to get a match 6 set.


