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Welcome! Need support, you got it. Or share your ideas and experiences.

RE: I did ;-)


Nice, on my model 9's, I warm them up for about 30 minutes with the gains turned all the way down. They also don't have metering that shows the exact bias, just turn the knob to the selected tube to be biased and bias. Before I do bias the output tubes, I make sure that the AC balance has been adjusted.

Even though you're biasing each tube individually, there're still push/pull and you might need to go through each tube a couple of times to really pinpoint them

I agree not to romantic, but very practical and one advantage is that if one tube does go bad or doesn't hold bias, you don't need to drop in a full set or pair when you have the ability to individually bias.

If you can find one or can get access to a TV-7 tube tester, you will be able to check your tubes. There are other less expensive tube testers, and it is a good thing to have if you do plan on buying vintage tubes. Don't be afraid to buy used vintage tubes as you can really save enough to more than pay for a good tube tester and verify the tubes you are buying.

It appears to me that you have a real good ear and you should be able to hear the difference from the 6SN7's that currently reside in there to some from the 1950's. The 6SN7 sort of went by the wayside around 1954 when the newer twin triode miniature 12AX7, and the rest of the "12" family of preamp tubes came into being. This doesn't mean that they totally disappeared and some of the best were made well into the early 1960's.

I put in NOS Mullard EL34's (xf2 production codes) in my amps and it did make a nice upgrade from what was in there. However, replacing the 6DJ7's with 6922 PQ's ( PQ= Premium Quality) , was even a bigger improvement in the soundstage. I eventually moved in some 7308's that are the cat's meow.

My point is, upgrade the 6SN7's first as they will will provide the most improvement.

You can mix or match your 6SN7's as they don't need to be biased and only need to be within normal limits for the tube itself. I mention this to let you know if you see a couple of nice or even an individual one, go for it/them until you build a full set for your amp.

Sorry for the ramble and hope some of it was worthwhile.


Nothing Sounds Better Than Tubes To My Ears! The Asylum where slander/libel is rampant...

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