Shootout of Nos 6sn7 tubes

highstream

Well-Known Member
Nov 16, 2013
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Not sure you're correct about this. The tubes are preamp (gain?) tubes in a Supratek Chardonay preamp. https://1drv.ms/u/s!AqsCKHVTj0ydpkGuRrV4BwVMgWXc?e=KMvFQ6
Since I recall that the gain tubes and cathode followers in my previous PrimaLuna Dialogue preamp could be heard to the tap, I checked some new production 6SN7's I have: the Tung-Sol 6SN7GTB that came with the preamp (early April) and had virtually no use and the Shuguang WE6SN7 I used until the other day. All could be heard through the speaker when tapped. That doesn't mean the Hytron version I wrote about isn't bad. It does sound different through the speaker than the other one when tapped, and *sometimes* when tapped seems prone to extra vibration or something causing the noise I mentioned, that goes on and on. The only other thing I can think of is that the preamp circuit doesn't like the CBS/Hytron GTB, although I wouldn't know why, since it runs well less than max.
 
Dec 4, 2019
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All tubes will be heard thru the speakers if tapped (mostly in the gain stage). A microphonic tube when tapped by fingernail or the end of a pencil will ping or ring like a bell and will also decay like an instrument. It may also pick up the sound of tapping on the component close to the tube and will be heard thru the speakers.
If none of the above, enjoy the music.
 

highstream

Well-Known Member
Nov 16, 2013
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Thanks for clarifying. In my set up, only two of the eight can be heard, the Hytrons. There's not much of a decay on those two, but the pitch between them is very different. One is fairly low, while the one being discussed here is much higher, hollow sounding.

Follow up: The developer of the preamp wrote:
Yes its just normal microphonics. Its amplified by the Chardonnays highish gain. If you use the gain control you can eliminate it. I actually think a bit of microphonics isn’t a bad thing. A lot of NOS are microphonic , some are really bad. The new production Tungsol, Sovtek EH have very rigid internals and don’t ring at all. The DHT tubes are all microphonic , might partly be the magic . Microphonics freaks a lot of audiophiles out, but it doesn’t worry me, tubes are organic and very complicated devices, they do a great job and should be giving a bit of leeway for their characteristics.
 
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Dec 4, 2019
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As long as there's no ringing sound between songs or quiet passages, I don't worry about a slightly microphonic tube.

If said tube starts to pick up ambient sound from the room or from the speaker it's time to trash it.
 

highstream

Well-Known Member
Nov 16, 2013
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That loud continuous hum I described, which initially occurred on its own and happens most every time I touch the preamp, requires that the unit be turned off to kill. It is apparently sign of maybe a loose or misplaced wire inside. I’ve asked for a replacement (the guy has a bag full).

Follow up (7/30): Turns out the bag doesn't contain any more CBS/Hytrons, or at least not for me. I've been mostly lucky on eBay with older tubes because the sellers have had good testers, but this guy's one didn't test for noise or microphonics. Tubes went back today. The Shuguang WE6SN7's, which are very good, have gone back in.
 
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Likes: Lowrider75

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