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

sls883

Showing 3 responses by larryi

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.    

I do hope you scored genuine Telefunken 803S tubes.  These days, they sell for up to $2,000 a pair.  The fakers have become increasingly sophisticated.  They use to offer their fakes at a price so low as to tempt even the wary.  These days, many of the fakes are being sold at the going rate of genuine articles which makes it harder to distinguish real and fake offers. 

With things like rare Western Electric transformers, the fakes use to be in too good condition visually to be realistic.  These days, the outer cases are rusted a bit to look old, but often the Western Electric decal is left in nice condition to tempt collectors.  A local builder who buys such parts on line prefers to buy such parts from sellers from Japan.  

There are instances where someone gets tubes for well below market price, so it is entirely possible for you to have real Telefunkens.  If they are not new in box, the price could be substantially lower than the price I mentioned.  The good news is that these tubes have a very long life, so even old tubes can be good for a loong time.

if you see the Telefunken diamond embossed in the glass on the bottom of the tube, that is a good sign; only the most sophisticated fakes have that embossed pattern.