I was checking the bias on my 1988 2203 head tonight after fitting a set of new GT EL34Rs. I was using a biasright type tool. On the first tube I got a reading of 25 ma. Way low so I set it to 38ma. I then measured the third tube and got a reading of 45ma. A bit high from what I have read but I was more surprised about the difference between the 2. I went back and forth a few times and left it at 35ma and 42ma. I have biased 2 power tube amps before and never seen more than 1ma or so difference between the pair. This is my first 4 power tube amp.
What could be causing this? The tubes are a proper matched GT quartet so they should be ok. Could something in the amp have drifted? What effect would a difference in bias like this have on the sound? I did not try the other 2 tubes - didnt seem much point if there is a problem with the amp.
Can anyone help?
Thanks
Neil
What could be causing this? The tubes are a proper matched GT quartet so they should be ok. Could something in the amp have drifted? What effect would a difference in bias like this have on the sound? I did not try the other 2 tubes - didnt seem much point if there is a problem with the amp.
Can anyone help?
Thanks
Neil