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
@elliottbnewcombjr I've tried several different input tubes as well as output tubes. I can hear noticeable differences. I'm pretty set on Telefunken ECC801S for input tubes. Siemens ECC801S being a close second. I hadn't tried very many different output tubes until recently. I now have a couple of pairs that work well. I just thought I'd try something different for grins. |
These days, for the exotic types and brands you mention (Siemens and TFK), I’d hazard a guess that there are more fakes than real ones on the market. I’d stay away from eBay as a source for such tubes. Most reputable dealers don’t pretend to have such tubes to sell. I assume you know that “ECC801”indicates a selected ECC81, even more rare than the run of the mill version of Siemens or TFK. What few exotic small signal triodes that I own I bought in the 1970s, so I know they are for real at least. However, maybe you are an expert in examining these tubes to prove to yourself that they are what they say they are. I certainly am not, even after 45 years in this hobby. To the question you did ask, yes I think 3000 and 2750 are sufficiently well matched sections. |
As lewn stated, one cannot tell by numbers what a tube will sound like. The sound will be determined by the particular amp and the particular brand and construction of the tube for any given type. Depending on the application, a tube can test quite poor, but can sound perfectly good in an amp that does not push the tube very hard. It may also sound like a sibling tube even if the two test very differently. I notice you are using very expensive Telefunken ECC801S input tubes. I hope you got it from reliable sources because the Chinese have become quite good at making fakes, including fakes with the raised Telefunken diamond in the bottom of the glass envelope. I got my pair for my phono stage a long time ago, and even then I worried about fakes. The boxes they came in looked very clean and bright, which worried me until I tried to open them and they started to fall apart from age. That was a good sign to me. |
@lewm @larryi Thank you for the replies. The Telefunken came with my LTA which I bought used. The seller seems to be knowledgeable about tubes. He paid $375 for the Telefunken tubes. He's a straight shooter, so I believe that to be correct. But, as far as my knowledge, I'm no expert with tubes. I'm learning. I buy from sellers that have lots of feedback and specialize in tubes. I guess I rely on their expertise and honesty.
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There are actually a number of test values that can be measured with a good quality tester. Although I am not sure any have sound quality correlations.
https://www.flickr.com/photos/jdflood/54409642846/in/dateposted-public/ |
