I’ve got a good assortment of these nos premium 12au7’s and 12ax7’s so I match them up as accurately as I can with my Hickok tester and use them that way. I really hear the difference in brand and era but not positive the matching is so critical but most experts would probably do what I do given the choice that I’ve accumulated
Tubes for a pre stage... matched NEW or unmatched identical NOS?
I have this question for so long:
On a integrated amplifier that uses a pair of 12au7 tubes (or alternatives) on the preamp section (Rogue Sphinx, for example) what is best option:
a) to have an unmached unbalanced pair of identical NOS tubes
b) to have of matched balanced pair of modern tubes
c) to have balanced 12au7 tubes no matter if they are matching
Once asked JJ why they didn’t offer matched 12au7 type of tubes and the answer was the it is irrelevant for the kind of use they are intended in audio circuitry. Is this right?
My question only makes sense when forced to keep tube-rolling costs down (or tube substitution when the stock ones fail) because the obvious and better choice is matched NOS, like those from Amperex or Mullard.
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The problem is what is 'well matched'? At the datasheet params? NONE of my tubes operate anywhere near them. I've bought plenty of NOS 'matched' 12AU7 & commercial variants. NOT one came close to the claimed Gm when operated at the amplifier parameters. NOR were the Gm matched at datasheet parameters. NOS tubes often have significant gas after ½c. on the shelf and need a while for the getter to clear it. Some advocate baking, but others say never. Induction heating may be the answer. Expect any NOS tube to change significantly over the first number of hours. Methinks Confirmation Bias accounts for a fair portion of NOS enthusiasm. |
Agree with @vthokie83 RCA Clear Tops are a fantastic tube at an amazing price. Way better than any new production that I have tried |
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