Weird 7591 Bias Current

It does sound remarkably well even with the GE tubes and their bias all over the place. It makes me wonder how much attention to matching they did back in the 60's. I can't to hear what this sounds like with new tubes...
 
I got the replacement set of EH7591'a today and they sound great! I have heard an original Fisher set of 7868's, a GE set of 7591's and a very expensive set of NOS RCA 7868's and I have to say these EH7591's sound great and are well worth the money. I was going back and forth deciding whether or not to go NOS or the Electro Harmonix and I'm very happy with the EH7591's. So, since I have replaced all the power supply caps and rectifiers, my pin 3 voltage is now right around 400v, maybe 405v tops. I have biased the EH7591's at 34ma…is that a good number or can I push them a bit more?
 
With 400-405V, 34ma gives you between 13.46 and 13.77w per tube.
36ma @ 400V is 14.4w
36ma @ 405V is 14.58w which is right around 75%.

You can go as high as 36ma comfortably with your voltages. But if 34ma sounds good, why push them, Unless you've got very deep pockets and don't mind purchasing output tubes every year stay between 34ma and 36ma.

Something to consider. Some tubes will drift on bias. So......set them for 34ma and let them cook for a couple weeks checking the ma every couple of days after running it for an hour or so. Write down ALL the voltages on each tube, and the ma's. (Your basically keeping a log of the operation of the tubes). NOTE ANY AND ALL CHANGES. You may have to reset the bias a couple of times before they actually settle down long term. Once they do check once a week for a couple months. If still stable, then once every 6 months. You want to document performance, any changes the tubes have made themselves and what you did to correct it. Seems like a lot of work, but you'll get more life from them this way. Don't go above 75% dissipation or 14.5W per tube.
 
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