I found the below clipping on the internet many months ago when I was shopping for 6SN7 tubes. I think you will find it useful for looking for good NOS tubes. Also there is a clipping from Tubeworld on what they feel are the better 6SN7 tubes.
I personally use the Sylvania 6SN7W in my preamp. It took the AE-3 DJH up several notches.
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6SN7 Audio Performance
This is the third update on the sound performance of the vintage 6SN7 types. I want to thank all the customers who have sent me their evaluations of these tubes. Let me stress that the optimum tube for your system will depend on your equipment and how your ears judge the tube's ability to reproduce live music.
Customers with Single Ended tube amplifiers and Atma-Sphere OTL amplifiers stated that the difference in performance was easy to hear. I did find it surprising that their final tube preference was very similar.
The general consensus is that the vintage 6SN7GT types, especially the 1940sVT-231s and “C” Military series(basically the same construction) sounded much better than 5692s and later GTA/GTB tubes in most cases. I must add that the 5692 is a very quiet tube with excellent speed, if you have equipment where 6SN7 tubes are microphonic, a 5692 may be the best choice.
I will again caution everyone that various 6SN7 types have different voltage and plate dissipation ratings. The voltage rating refers to voltage across the tube's plate and cathode. To ensure good tube reliability you should probably run a tube at 70% or less of its maximum plate dissipation.
5692 - 275 Volts maximum & maximum 1.75 Watts per section
6SN7GT/WGT -- 300 Volts maximum & maximum 3.5 Watts per section
6SN7GTA/GTB - 450 Volts maximum & maximum 5.0 Watts per section
Using the general audio application of 250 plate volts, a bias of 8 volts results in 9ma of current and a plate dissipation of 2.25 Watts, we find:
5692 - runs 43 % over maximum rating – It isn’t a 10,000 hour tube when you run it this HOT!
6SN7GT - runs 64% of maximum – coasting and liking it
6SN7GTA/GTB - runs 45% of maximum – Hardly turned on, may outlast you.
When in doubt check with the manufacturer of your equipment. If they provide a schematic with component values and voltages, it's easy to use Ohm’s law to calculate the current and dissipation.
There really is no reason for manufacturers not to provide this information.
Here are the rankings. If you have anything to add, email me and I will add it to the list.
VT-231 Tung-Sol, round black plates - Clean, fast, the best in everything, wide bandwidth, great resolution. If you can’t find the Music, it’s not the tube’s fault.
VT-231 RCA, black plates, rich harmonic structure, beautiful timbre and voicing, wide soundstage
6SN7W Sylvania (Mislabeled by me as the 6SN7WGT), black plates – Tied for second and came in first if your system sounds a little laid back, especially some single ended amplifiers – Excellent low level detail resolution, very immediate sounding with a lot of Slam. There are three types of these tubes, two large bottle types, one has a metal ring and one smaller bottle with s smaller plate structure. The smaller one has better low level detail and the larger ones have more slam.
VT-231 Raytheon, black flat plates - like the Tungsol a little sweeter, nice balance of detail and timbre
VT-231 Ken-Rad, flat black plates - Great Bass, drive, sweet midrange, good bandwidth and
VT-231 Sylvania, black plates, wide bandwidth, well balanced, excellent sound stage and air
VT-231 National Union - good drive and great midrange, softer bass and a touch euphonic
6SN7WGT, Tung-Sol. Black Plate, brown base – Sounds similar to the Tung-Sol VT-231, not as clean
6SN7WGT, Tung-Sol. Black Plate, brown base – Very good bandwidth, bass, detail and soundstage,
6SN7GT, CBS/HYTRON Black Plate, quiet and musical, the best of the non-military tubes
6SN7GT, Ken-Rad, black base, bass a little tubby, but clean with great ambiance and air
6SN7GT, Sylvania Green Label, first top getter on the list, non-fatiguing, smooth, with good detail resolution and bandwidth, plus its easy to find and afford.
6SN7GT, RCA Black Plate, still a side getter, rich harmonic structure and maybe a little too sweet.
* 6SN7GTB, Sylvania Green Label, rich harmonic structure, good midrange, decent soundstage
6SN7GTA, General Electric Black Plate, the great driver tube? Fast, wide bandwidth, smooth sound at the expense of the of low level detail. Along with the Sylvania 6SN7GTB, a great “fourth” tube in Atma-Sphere amps.
6SN7WGT, Sylvania Green Label, Top Getter, “silver top” , very clean with great detail resolution and speed. Bass can be a little tubby and midrange a little congested.
6SN7WGTA, Sylvania black base green label, clean and fast with great drive, good bass
5692, CBS-Hytron, fast, good dynamics, lot of air and great timbre
* 5692, RCA Red Base, very warm sweet sound, great on voices and jazz
6SN7GTB, RCA, rich midrange, warm sound, likes being combined with other 6SN7 types, likes the Atma-Spheres
6SN7GTB, G.E, Gray plates, work horse, lacks refinement, a good tube
It’s surprising how many 6SN7 types came out above those expensive 5692s.
One thing became clear based on customer feedback, combining 6SN7 types seems to work better than using all 6SN7s of the same type. With so many preamps and amps using this tube, you can end up with
Six 6SN7s per channel. It appears combining tubes like the VT-231s as voltage amplifiers and 6SN7Ws or 6SNGTA/GTBs as driver tubes you gain the strengths of all. Using one type seems to accentuate the tube’s weaknesses.
Yes there are a lot of 6SN7 types not listed, many of them very good tubes. Based on my own personal experience and customer feedback, the Brimars and Mullards(except for the B65), are good tubes but do not offer the performance of the best US vintage tubes.
The currently produced tubes are about as musically satisfying as a “Boom Box”. I can’t understand why today’s manufacturers don’t just copy some of the great ones. If you are out there, Russia, I will provide free samples. You did it with the 12AX7LPS, do it with the early Tung-Sol, RCA and Sylvanias….Sorry just had to stand on my soapbox for a second.
Best Regards, Dennis
Dennis Boyle, email chimera1@mail.idt.net
Chimera Laboratories -
www.ChimeraLabs.com/~CL/1414 South Akard Street
Dallas, TX 75215
TEL: 214-428-3901
FAX: 214-426-6605
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FROM TUBEWORLD
BEST SOUNDING 6SN7 AND EQUIVALENTS (6SN7GT/GTA/GTB/WGT, 5692) ARE THESE:
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ECC33=CV2821 Mullard (direct 6SN7GT equivalent, superb sound, the best overall, 1950's)
ECC32=CV181 Mullard (can be used in certain applications in place of a 6SN7, superb sound, 1950's)
6SN7W Sylvania "crome top" 1940's (metal base and black base)
6SN7GT/GTB/WGT Sylvania "chrome top" 1940's-1950's
CV1988=6SN7GT/GTY Brimar England 1950's and early 1970's (Y=brown base)
6SN7WGT Raytheon ribbed plates 1950's
VT-231=6SN7GT Sylvania, Tungsol, Ken Rad, RCA 1940's
5692 RCA Red Base (early 1950's are best)
5692 CBS-Hytron and Sylvania Brown Base (1957-early 1960's)
6SN7GT/WGT Tungsol 1950's-1960's
6SN7GTA GE early 1950's (black plate)
6SN7GT RCA early 1950's
6SN7GTB Sylvania late 1950's-1970's
6SN7GTB RCA late 1950's-1960's
6SN7GTB GE side-getter late 1950's-1975
6SN7WGTA Philips USA made by Sylvania 1970's-1980's
6SN7GTB RCA, Sylvania, GE coin-base 1970's-1980's
6SN7GTB Japan 1970's
6SN7 Russian (harsh highs, thin sounding)
6SN7 Chinese (junk)
