@lewm +1
Do vacuum tube test values reflect sound quality?
I recently ordered a pair of output tubes to try in my LTA MicroZOTL preamp. Two Sylvania 6SN7WGT tubes, Gold Brand. I’ve had good luck with Sylvania 12sn7gt bad boy tubes, so I thought I’d give them a try.
After I bought them, I saw a similar pair for more money that had slightly higher test values. Does that mean they might sound better or that they just have more life left? What properties do you look for in tubes?
Below are the values of the tubes that I bought.
Tubes are matched for dynamic gain and structure, testing at 3000-2750 and 3000-2750 where pass/fail is 1625 micromho. They have the same structure inside and out, having matching date codes of "922", the 22nd week of 1959
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- 37 posts total
@larryi You made me curious, so I pulled one. There is a diamond on the glass bottom. |
@lewm one section of a dual triode could be used for the gain stage and the other section could be used as a cathode follower in a single ended preamp. So both sections still being used. |
How a tube sounds in any given amplifier, especially a preamp level tube, highly depends on how much local feedback is used on the tube in that specific circuit. Generally, high gain stages, like the first stage of a phono preamp, use little if any feedback on the tube. In a cathode follower circuit, there is nearly 100% feedback giving little if any gain, but a much lower output impedance which, of course, is the reason for its existence. In other words, high gain stages are particularly fussy about the quality of a tube whereas low or no gain stages with lots of feedback like cathode followers are pretty much agnostic about the providence of the tube. |
- 37 posts total