A few weeks ago I purchased a tube bias probe from Amazon... the probe is actually from Eurotube. Anyway yesterday I cleaned off my work bench enough to crack open the head and got down to see what I could see I found one tube to be reading 34 to 35 milliamps and the other to be reading 22 to 23 milliamps. Ok so I know a 12 milliamp spread between the 2 EL34s wasn’t good. The tube seemed to be original and were dated 2008. I bought the amp used in 2015 and never changed anything. I remembered I had a new never been opened set of EL34s that’s been setting around for 20 years or more. I figured I’d put those in and see what happens. The milliamp readings on the new set was less then 2 milliamp difference. Yeah Dawg I was on to some thing! So with the new matched set I performed the following calculations. 1 EL34 = 25 Watts Plate Voltage = 460Volts RMS = .7 25/460 = 0.05434 0.5434 X .7 = 0.03805 or 38milliamps So the correct bias setting for the amp is 38 milliamps. Yay! If I did it correctly. I set the reading as close as I felt I could get with one tube reading 38.5 and the other reading 37. And this is where I left it. I played for a while last night at all volume setting. I honestly can’t say if I can hear any difference... but it felt different. It felt more responsive and more articulate... but it could all be in my head. I PM’d forum member @Robins to see what he thought of my work and setting. He seems to think I did good! So I’m leaving it alone. I sprayed the pots and jacks with cleaner. Tighten up the bolts on the trannies. Cleaned the muck off the Plexi front and back. I think I’m done!