2. amps-preamps
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NOS Tubes - Ecstasy or Agony

I have been running tube amps for many years and have built a number of SETs and other tube amps, kit's mostly.  My main power tubes have been 2A3's and 300bs and I have used mostly new manufacture tubes including JJ's and EML 300b's (great tube btw).  I did use NOS driver tubes and headphone amp tubes.  Never really had a problem.

I just transitioned to a Don Sach's 6sn7 based preamp and McCormack SS power amp.  The preamp is very nice and sounds great with Shugang tubes. Of course, I wanted to try some NOS tubes, went online and did my research.  Now the DS2 is a great preamp, the drawback is it uses 4 6sn7s and so I need to get pairs.  Would  have love to get my hands on the Dehavilland, uses one tube!

First Pair - I ordered some Sylvania's from TC Tubes. Advertised as 50's vintage, ,when I received  them they were marked 60's. Hmmm.  So I tried them and they sounded pretty darn good except after a couple hours one of them developed a high pitched hum, like a florescent bulb. So I sent them back.  

Second Pair - ordered from Brent Jesse - has a good rep online and a really informative website.  Received them and one was dead on arrival, they were also clearly of different construction. So they are going back.

Next will try Andy at Vintage Tubes Services, he also has a solid  reputation so hopefully I can get something that works.

I am curious what experiences others have had. Maybe its COVID, or are these dealers just unreliable, or is just 6sn7's?  Really thought I could just buy some NOS tubes and experiment, I can't even get two to work.

I don't really want to disparage these dealers but I do think all the claims of testing are maybe overblown.
drewh1

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
12,088 posts
 
I wonder if something about the circuit in my preamp is especially sensitive to microphonic tubes.
@drewh1 
It probably is. If that is the case, you have to handpick the tubes for low microphonics. Its a good idea to specify that to the supplier; if they can't do it than you'll have to- by buying tubes, trying them out and sending them back if the microphonics are unacceptable. Keep in mind that all tubes have microphonics so its not a matter of getting rid of them as it is getting them low enough that they are not noticed. If operating the front panel controls of a preamp can be heard then I would consider that unacceptable.
atmasphere's avatar
atmasphere
12,088 posts
 
NOS Tubes - Ecstasy or Agony
Yes :)
@drewh1  We use a lot of 6SN7s in our circuits both in preamps and amps. The Shugang tube is a copy of the Phillips JAN tube made in the late 1970s and early 80s and sounds almost the same. The Shugang factory burned down in August of 2019 so these tubes are becoming scarce. I understand they will be setting up production again though.

The JJ tube is pretty decent FWIW.


If you like to play with older tube types a tester is a good idea, even if the tubes are coming from a good source like Andy at VTS.


Our customers have commented that the Psvane 6SN7s have all the best qualities of the NOS tubes without the weaknesses. That's a pretty serious statement! I've heard the same thing about the Sophia tubes, but at least in our gear, we've only seen them run about 6 months and our gear isn't that hard on 6SN7s- we've seen the Chinese tubes go for years.


The 1960s Russian 6SN7s are quite good. The later Sovtek tube looks very similar but is arguably one of the worst 6SN7s IMO. Its rare to see the newer Russian made 6SN7s not show some leakage on the tube tester.


So far the best comments we've heard from our customers on NOS 6SN7s have been about the Sylvania metal base Chrome Dome (which dates from WW2), the KenRad and the RCA redbase (which is nearly the same as the CBS Zalytron).



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