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6SN7--continuing on a new thread

post #1 of 6
Thread Starter 

I was astonished by the number of posts on the 6SN7.   As a designer of high-end tube audio gear (coffmanlabs.com) I thought it worth sharing my experience from the design side. YMMV  And just to make it clear--I do plan offer some of my products with the 6SN7; I have around 4,000 to 5,000 vintage pre-1970's 6SN7's sitting in boxes in my storage.

 

The 6SN7 has some of the lowest 2nd harmonic distortion available when run at the right parameters.  However, there are very good alternatives.  The 6CG7/6FQ7 (and 8CG7) are viturally identical and test out nearly identical to the 6SN7 in every respect from the audio perspective.  If the 6SN7 is too expensive, the 12SN7 is a great alternative as well.  And don't forget the 6J5 which is 1/2 of a 6SN7.

 

However, I actually do not like using the 6SN7 as a driver tube for high-voltage hungry SET tiodes (300B, 2A3, 845--etc.)  The 5687 has better distortion charactaristics at high drive voltages, and because of the low plate resistance it is perfect for choke loads. Another equivalent circuit, if you must use the 6SN7 is to drive a power triode, is to use a 6SN7 to drive a 12B4 and let the 12B4 do the heavy lifting.  (The 12B4 is one of the all time under-rated tubes IMHO.)

 

Where I do like the 6SN7 is as a driver tube for typical pentodes like the EL84, EL34, 6L6, 6V6 and the like.  As an input buffer tube it is great.  I wouldn't use it for the basic drive tube for a pre-amp because an additional cathode follower is needed to get the low output impedance in a typical circuit.  I'm not a fan of cathode follower circuits, or any circuit that uses feedback.  No matter how good they are I can hear the change to the phase in the harmonics--left over habit from my classical violin days.

 

My favorite 6SN7: That's easy--the TungSol round plates.  Unfortunately, I sold my last pair to Korea for $1000+ when I needed some new manufacturing equipment during the Coffman Labs startup phase.  So my second favorite--and the one I turn to--is the Raytheon Black Plate 1960's vintage VT-231 Mil Spec.  Most neutral and realistic, again IMHO.

 

Again, all these opinions are heavily colored by my experience, listening preferences, and the rest of my system.  I don't expect them to necessarily fit with everyone else, but you may find them interesting.

 

Cheers!

 

Damon Coffman

Coffman Labs

post #2 of 6

True hobbyists, tube lovers and fellow Head Fiers sell tubes at no or very little profit.

If you look at the for sale ads you won't see many Head Fiers selling a pair of TS 6SN7 BGRP for $1000+

 

Head-Fiers don't make profits from selling tubes and gear but try to give others the opportunity to own some nice gear and enjoy the hobby. 

post #3 of 6

Excellent post.  This is why I specifically hang out here--to read the posts and experience the generosity of Silent One, 2359Glenn, Clayton SF, ultrainferno, Skylab (who sold me a brilliant amp at a HUGE discount), Longbowbbs, and you Stavros.  (If I left anyone out, it was just an oversight).

 

Quote:
Originally Posted by rosgr63 View Post

True hobbyists, tube lovers and fellow Head Fiers sell tubes at no or very little profit.

If you look at the for sale ads you won't see many Head Fiers selling a pair of TS 6SN7 BGRP for $1000+

 

Head-Fiers don't make profits from selling tubes and gear but try to give others the opportunity to own some nice gear and enjoy the hobby. 

post #4 of 6

Dont forget Oskari, that guy is a human encyclopedia on tubes.

post #5 of 6
Thread Starter 

Realize that--I'm not selling tubes here.  Just noting that the Round Plate 6SN7 Tungsols are basically unobtainium these days.

post #6 of 6
Quote:
Originally Posted by hodgjy View Post

Excellent post.  This is why I specifically hang out here--to read the posts and experience the generosity of Silent One, 2359Glenn, Clayton SF, ultrainferno, Skylab (who sold me a brilliant amp at a HUGE discount), Longbowbbs, and you Stavros.  (If I left anyone out, it was just an oversight).

 

 

Thanks for your kind words.

We are a multinational and multicultural group of hobbyists from all over enjoying the hobby and trying to help.

 

Quote:
Originally Posted by Neogeo333 View Post

Dont forget Oskari, that guy is a human encyclopedia on tubes.

 

Indeed our European tubes expert!

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