Hello all,
i am new to tubes and looking at some at some vintage tung sol/sylvania 12ax7's. they were tested on a tv 7 tester and the supplied numbers are 40/40 and 68/70. is that to much of a spread to use together in my phono stage? thanks in advance!
I'm not familiar with the TV7, but the results don't mean much by themselves. You need to find out the minimum good value and what a new 12AX7 tests on that unit, so you can have reference numbers to compare. For example, if the minimum good is 30 and a new 12AX7 typically tests around 50-52, then the numbers you gave will have a context at least. Secondly, you don't know if these tubes are noisy, so the best way is to try them on your phono stage. Usually, a lot of these vintage tubes have not been used for a long time, and may have developed oxidation. Oxidation can make a tube noisy, so cleaning the pins is a good idea. Finally, the 12AX7 is not the quietest tube in a phono stage. It is better to use its low noise variant, the 7025 which was designed for hi-fi applications whereas the former was not. If you want a current production tube, then the 12AX7LPS would be a good low noise option. Hope this helps.
