SEX tubes

[mcandmar]

There are really only the two types, Sylvanias, and everything else.  They have slightly different characteristics, Sylvanias are slightly better on the low end, the rest are better on the high end. Its worth trying both for yourself to find which you prefer.  I also find the Sylvanias to have a nicer midrange.

There is a third variation, the holy grail tube as i call it, of which i only have one set.   They are marked as Sylvania Export in gold writing, coin base bottle, with the tall skinny Sylvania plate for the 1st section, regular GE/RCA style secondary plate in grey, and GE/RCA Mica spacers. They have the low end response of the regular Sylvanias, and the high end response of the GE/RCA/TS.  The best of both worlds if you like, and they also measure insanely low THD distortion levels.  Where most are 2-3%, these measured below 1%.  They are a bit of a mongrel in there build, and out perform everything else in every measurement i have done on them.

Other trends i have noticed that are worth noting, coin base tubes measure lower distortion than regular tubes.  And Sylvania tubes measure a higher transconductance than regular tubes. There doesn't seem to be any difference between grey or black plate RCA/GE tubes.   Tubes with series heaters tend to be noisier.  You can tell i have tried a few

[dmhenley]

Appreciate all this insight - thank you.
I'll keep an eye out for some of these elusive beasts.

Seems cap rolling is a more effective (potentially expensive) and accessible means to tweak. Based on available parts, etc.

[Loquah]

There are really only the two types, Sylvanias, and everything else.  They have slightly different characteristics, Sylvanias are slightly better on the low end, the rest are better on the high end. Its worth trying both for yourself to find which you prefer.  I also find the Sylvanias to have a nicer midrange.

There is a third variation, the holy grail tube as i call it, of which i only have one set.   They are marked as Sylvania Export in gold writing, coin base bottle, with the tall skinny Sylvania plate for the 1st section, regular GE/RCA style secondary plate in grey, and GE/RCA Mica spacers. They have the low end response of the regular Sylvanias, and the high end response of the GE/RCA/TS.  The best of both worlds if you like, and they also measure insanely low THD distortion levels.  Where most are 2-3%, these measured below 1%.  They are a bit of a mongrel in there build, and out perform everything else in every measurement i have done on them.

Other trends i have noticed that are worth noting, coin base tubes measure lower distortion than regular tubes.  And Sylvania tubes measure a higher transconductance than regular tubes. There doesn't seem to be any difference between grey or black plate RCA/GE tubes.   Tubes with series heaters tend to be noisier.  You can tell i have tried a few

I've been absent from these forums for a while and coming back to see such awesome information only confirms that I shouldn't have strayed so long. Thanks for the amazing information, mcandmar - now I have to go tube hunting! 

[mcandmar]

Welcome back

[dmhenley]

Found a couple coin based RCA - grabbed them on Ebay. Should have them next week.
One of my current RCAs gave up on me.

[dmhenley]

Got the RCA coin based tubes in tonight. Letting them play for a bit.
Construction appears to match my other RCAs.

[Adrian]

I have been listening to my new 6DN7s for about 10 hours and I forced myself to put down the headphones to post this.

I had previously used the best pair I had:  one RCA and one Sylvania because of their combined low noise floor and best sound.  I tried many combinations of RCA, GE, and Sylvania.

But now.... I have found the best 6DN7 tube yet.
These tubes have the lowest noise of any I have and they are better matched, channel-to-channel.

They are damn-near holographic.
I am currently using them with a pair of NAD VISO HP50s and I am now hearing imaging that was never there before.

Here are these new tubes that have found a home:

[Doc B.]

Yeah the Tung Sols are a little bit better than the other 6DN7s. I had some in my own SEX amp for many, many years. But I wouldn't say it's enough of a difference to pay exorbitant money for them.

[Adrian]

Dan
These Tung Sols are head and shoulders above what I have found to date.
Perhaps I have not been fortunate enough to have better sounding Sylvanias, etc.
Anywho, I do not have the desire to do tube rolling in the S.E.X. for now!
I will be prepping some parafeed caps to try but I will get a couple of months on these tubes before I do.

[mcandmar]

Interesting findings.  I measured the TungSols for frequency response and distortion and i couldn't see any difference between them and the regular RCA/GE tubes, yet for some reason my ears told me they sound slightly cleaner.  I just put that down to my imagination and moved on.

One thing you do not want to do is mix regular GE/RCA tubes with Sylvanias as they have a fairly different frequency response, i would imagine it would sound a bit disjointed mixing them.

Happy holidays all!

[Adrian]

Thanks mcandmar
I tried many combinations of the tubes on hand with the lowest noise (I wanted the S.E.X. to be as dead quiet as my Crack/Speedball).

I fell upon the RCA/Sylvania combo that sounded the better of the various combinations.

Measurements do not tell the whole story - I believe that subjectivity is King in this hobby (or maybe I'm just blissful in my ignorance).

[sbelyo]

I love the tung sol tubes.  They have great balance and detail.  The sylvania black plates are very close, a little less deatail but deeper bass.  I have a matching date code pair of sylvania grey plates that sound very very good as well but different than the tung sols and the black plates.  It comes down to using the pair that sounds best to you.