[adhoc]

[size=medium]- Headings and important sections in RED
- Color of opinions quoted corresponds to original thread.[/size]


[size=medium]6SN7 variants:[/size]
[* = definitely a safe 6SN7 substitute]

ALWAYS ASK YOUR AMP MANUFACTURER FIRST BEFORE SWAPPING TUBE TYPES!!!

6SN7GT* - First designation of the 6SN7 tube type. ‘G’ = glass body & ‘T’ = short bottle.
6SN7W* / 6SN7A* / 6180* - 10000hrs minimum life. Often labeled with JAN-CHS (equals Sylvania-made military stock) The A is generally a taller bottle with the mica above the metal band while the W has the bottom mica a bit below the metal band. But it's common to find both labelled as each other also.
6SN7GTA* - 'Upgrade' of 6SN7GT, max 450Volt Ua, 5W per system and 7.5W total. Hence tube better fulfills special requirements for TV sweep applications, like higher peak power and better impulse capabilities.
If your amp is designed around this tube, you MAY NOT be able to substitute in other 6SN7 versions due to the higher ratings for this tube – check with your manufacturer.
6SN7GTB* - Same as GTA, but with faster tube heat-up (11 seconds only).
If your amp is designed around this tube, you MAY NOT be able to substitute in other 6SN7 versions due to the higher ratings for this tube – check with your manufacturer.
6SN7GTC* - Metal envelope type 6SN7 [ie. glass envelope replaced by a metal cap]. Not well regarded. From Audio Asylum: ”South American trash can style 6SN7, 1970's vintage, pure rubbish, I wouldn't even count on it really being a 6SN7 as the South American tube makers were fairly...'liberal'...with their use of tube numbers.” –Robert H
If your amp is designed around this tube, you MAY NOT be able to substitute in other 6SN7 versions due to the higher ratings for this tube – check with your manufacturer.
6SN7GTY* - Only found on 6SN7GTs with brown ‘low-loss’ Micanol bases. RCA (US - lighter brown) and Brimar (British - darker brown) made GTYs.
6SN7WGT* - Military version of the 6SN7GT; 10,000hrs minimum life (up for debate). “IMO, while tubes (like car engines or light bulbs) may be rated for a specific lifetime, a LOT depends on the actual usage type and pattern the tube will see. E.g. Switch your amp on/off 10 times a day? Don’t expect 10,000hrs.” -Author
6SN7WGTA* - Military version of 6SN7GTA.
6SN7WGTB* - Military version of 6SN7GTB.

VT-231* - Military Part number for 6SN7. Part number used until 1945 - hence presence of this designation is usually a guarantee for real old tubes.
JAN-XXX-6SN7* - JAN= Joint Army Navy. Factories conducted stress tests (above normal 'civilian' specs) on samples of standard tubes. If they survived, the whole lot would be approved (batch approval), and marked with the prefix JAN. The samples that are actually used for the stress tests are discarded. Do remember that the stress tests conducted were on SMALL samples. “ Very interesting thing nobody talks about - especially dealers who have made a living buying old military stock that occasionally pops out of warehouses. What did the government do with tube shipments they received where their spot testing results were not acceptable? Well, in some cases, they sent them back, whereupon the manufacturer sold them into the secondary markets. A lot of those are still floating around today. OR - the government stuck the shipment into a warehouse, and in typical bureaucratic fashion, forgot about them - until some SoCal slickster approaches them with a great offer. Bingo! They are back on the market as super-duper cold war commie beating top grade mil-spec tubes - and sold to you and I, who don't realize that they probably failed the spec test. The VT or JAN designations have too often been assumed in tube folklore to be better tubes. In reality, they may be the rejects. I have occasionally found FIELD STOCK in foreign countries left behind after a war. This is the primo stuff. Not the stuff sitting in a US or UK warehouse.” –Robert H. [PHOTO HERE]
5692 - Military part number for a 'shock-proof' tube. Introduced 1948. The famous RCA "red base" is a 5692. Weight is much higher, and tube construction differs from 6SN7s. 275V maximum plate voltage & maximum 1.75W per section. [PHOTO HERE]

33S30A* / 33S30B* - Swedish military versions of the 6SN7. Very very rare and sought after.
ECC31, 32, 33, 34 - Popular MISconception: these are NOT equivalent to 6SN7. Especially the ECC32/CV181 - close, but the 50% higher current draw will probably fry some transformers. Grid voltage, gain and transconductance are all different for these tubes. Ask your amp manufacturer first before substituting these in.
CV181/CV2821 – Alternate designations for ECC32/ECC33 respectively. The popular Mullard CV181 is NOT a drop-in replacement for 6SN7s – 50% more power draw means that the tube will probably send your transformer up in smoke.
1633/6042 - 25V/0.15A heater version of the 6SN7.
6N8S* - Old Russian designation for the 6SN7. Some Eastern European and Chinese tube factories still use this designation.
6H8C - Russian designation for a 6SN7 with a higher plate voltage. [PHOTO HERE]
13D2 - Europe-only 'special quality' version of the 6SN7GT. The tube is reinforced for additional mechanical rigidity. [PHOTO HERE]
CV1986* / CV1988* - Both are the UK Government Common Valve designation for the 6SN7GT. [PHOTO HERE]
CV2627* - UK Government Common Valve designation for the 6SN7W.
B65* - 6SN7 replacement made by Marconi/Osram/GEC. Extremely rare and sought after. [PHOTO HERE]
7N7 - Electrically IDENTICAL to the 6SN7 tube. This tube has a loctal-base. To fit a 6SN7 socket, a loctal-socket-to-octal-base adaptor must be fashioned. Why loctals? These tubes were created (and strongly advocated by RCA and Philco) for use in high-frequency radio applications, where the longer wires present in normal 6SN7 bases were causing problems by picking up interference. [PHOTO HERE]


Some words on tube reliability:

To ensure good tube reliability you should probably run a tube at 70% or less of its maximum plate dissipation.

Using the general audio application of 250 plate volts, a bias of 8 volts resulting in 9ma of current and 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.

Words of Wisdom:

● “It may be possible to get genuine Sylvanias or Tungsols labelled as something else; for instance I've seen a Tungsol roundplate labelled as Emerson and a genuine Sylvania VT231 labelled as Ferranti.They may be cheaper if they are labelled like this.” – Rob N

● And a counterpoint to the opinion stated above. “Sometimes true, not. In many cases that secondary branding was a legitimate aftermarket sale. In many other cases is was a dumping of tubes that failed to meet spec to a rebrander to liquidate under a name not associated with the original manufacturer - a tertiary market to dump 'grey' tubes. Yup, they were always cheaper. Rightfully so.” –Robert H.

● "In tubes WITHOUT top getter flashes, small metallic splotches (which look similar to getter flashes) on the inside of the glass above the heater filament openings indicates that the tubes are USED; tungsten from the heater evaporates with use and condenses there." -author

● And a counterpoint to the opinion stated above. “Again, often true, but certain tubes - particularly short bottle GE's from the 50's - develop these splotches virtually immediately upon testing and so this cannot be considered a real sign of use for those tubes.” –Robert H.

● “In general – a ‘W’ suffix anywhere behind the tube type number indicates a low-microphonics version of that tube.” – various

● "The "getter flashing" absorbs free oxygen, nitrogen, carbon dioxide, carbon monoxide and hydrogen from the tube whether the tube is used or not. You can be certain the vacuum is bad "ONLY" if the flashing turns chalky white all over. If it is silver, black, rainbow-colored, or even totally gone, the tube might still work fine. In fact, a "BLACK" getter is MORE effective than a "SHINY" getter at absorbing gas.

● Here's a quote taken from "GETTER MATERIALS FOR ELECTRON TUBES" by Werner Espe: "If the getter is vaporized very slowly, the first barium atoms evaporated will absorb the gas present so that the remaining getter is deposited in a very high vacuum, exhibiting a "shiny" mirror. If flashing is done very rapidly, however, the getter deposits in a rather high vapor pressure, and the getter mirror will be discolored (rainbow-like) due to the dispersion of the barium. If vaporization is carried out in the inert atmosphere of a rare gas, the condensed deposit will be "black", resulting in a "dispersal" getter. This condition does not mean that the getter is contaminated, but merely that the deposit is finely divided and therefore absorbs light. Such deposits exhibit "HIGH" efficiency than the bright deposits: i.e. DARKER is better.

The ONLY way to accurately determine the health of a vacuum tube is to test it ELECTRICALLY. PERIOD. Anyone who discards a tube because its getter flashing is slightly "discolored" is making a sad mistake." - Tubeseller.com

● “It's also worth knowing that there is a common misconception about those VT-231 numbered tubes. It's nothing more than a number. If you find a 6SN7GT of the same vintage, it will be identical to the VT-231 numbered version. I have here Sylvania 6SN7GT from 1945 identical to the VT-231 numbered tube, and Raytheon 6SN7GT 1944 identical to the 1944 VT-231. Also RCA's, Tungsols, and so on. There is no magical significance to the VT-231 number. But some people think there is, because salesmen have told them so. It's become popular folklore in tube circles.” – Tubeseller.com
[size=x-small]
JAN codes (JAN-xxx-6SN7 / 6SN7x / 6SN7xx / 6SN7xxx)
[IF there is an added designation ‘VT-231’ = WW2 vintage, roughly made till 1947]

GE: CL (JAN’ed GE tubes are rather rare)
Hytron: CHY (merger with CBS came after VT-231 designation, hence no 'CBS/Hytron' yet)
Ken-Rad: CKR
Sylvania: CHS
Raytheon: CRP
RCA: CRC
Tung-Sol: CTL[/size]


A few words regarding the Mullard CV181:

This tube is highly sought-after. BUT, it is NOT a 6SN7. It is an ECC32, which is NOT a drop-in replacement for 6SN7. As mentioned earlier, the current draw for this tube is 50% higher than a 6SN7. This will blow most power transformers over time. And power transformers rarely die alone – they usually take some other parts with them when departing this plane.

The higher current draw also results in higher gain – something which many people forget when trying out this tube. All other factors remaining constant, a higher gain results in a higher volume, which can in turn result in the (mistaken) impression that the tube has a ‘fuller’ sound.

Which may or may not have contributed to this particular tube’s much sought after status. Food for thought, indeed.

“It's interesting to note that a single dealer created virtually the whole myth and market for the CV181. He made a lot of bucks off them because he had an almost limitless South African source for the tube.” Robert H.




[size=large]-= THE 6SN7 REFERENCE LIST =-[/size]

Opinions are distilled from these pages:

6SN7 VT-231 5692 Tube Audio Performance – Chimera Labs Revised 05/2003: http://home.att.net/~chimeraone/6sn7sound.html

Singlepower tube rolling thread: http://www6.head-fi.org/forums/showt...er+tuberolling

PPX3-NS67+ upgrades or MPX3?: http://www6.head-fi.org/forums/showt...sylvania+6sn7-

View Single Post – MPX3 Upgrade (Glod): http://www4.head-fi.org/forums/showp...0&postcount=24

Tuberolling the Wheatfield HA2: http://www4.head-fi.org/forums/showt...highlight=5692

MicroZOTL tube rolling thread: http://www4.head-fi.org/forums/showt...highlight=5692

Tuberolling the Eddie Current HD-25: http://www4.head-fi.org/forums/showthread.php?t=120460


4 SECTIONS:

1. VT-231 TUBES[*]
2. NOS TUBES
3. NEW STOCK TUBES
4. 5692 TYPE TUBES
5. VTV’s TUBE RANKINGS (from ISSUE #11)
[*]: I have received some flak over giving a separate section to what is essentially an inventory control number, perhaps implying a certain “mystique” about these tubes/ Remember people - THERE IS NONE. Just as there are “good” and “bad” 6SN7s there are “good” and “bad” VT-231s.


- 1. VT-231 TUBES

Hytron VT-231 [PHOTO HERE]
[black base, black plates, bottom getter, rectangular top and bottom micas]
● “Hytrons [are] slightly less forward and colder than the Sylvania's (VT-231s).” -Glod

Ken-Rad VT-231 (also available with ‘US Navy’ label) (1940s vintage) (2 types- parallel or staggered [ie diagonal pattern of grid posts on mica when viewed from the top] plates. Staggered are preferred.) [PHOTO HERE]
[black glass ending ~7mm above base, white labels, staggered/parallel plates, bottom getter (still visible), may have no labels on black base]
● “Great Bass, drive, sweet midrange, good bandwidth” –Chimera
● “the Ken Rad VT-231 is often referred to as the very best 6SN7 for low end [referring to bass, not low-quality equipment], and I've heard nothing to contradict that” –Hirsch
● “40's should be the same as the VT-231 designations with staggered plates. Lots is written about this tube. I agree with most of what's written online. 40's KR, in either clear or black glass with staggered plates and bottom getters, are good tubes. Bass is definitely it's strong suit. On the other hand, the highs are more grainy then other tubes. Consider this tube the antithesis of the Sly VT-231s. Some say it's got a sweet midrange, but in my application it isn't (even bordering on lean).” –Len
● “good midrange, not as rich as Sylvania, excellent highs, known for powerful bass.” –Hirsch, in personal correspondence with author
● “The month I spent waiting to get this tube where rewarded with the best bass performance of any tube I have yet tried.the bass is amazing,tight,accurate and very focused.Output tube matching becomes more important with this tube but the reward is the incredible bass.There is no real loss of soundstage or midrange dynamics from the 5692 brownbase but some of the bass comes at the expense of vocal clarity.an awsome upgrade.” –Tuberoller
● “OK, there's the bass. This particular 6SN7 is a monster. Great bass response on the R10...but with any other headphone can be overwhelming (depends on 12AT7)...but the midrange and highs seemed to suffer. Tonality was great, but the ZOTL seemed to have problem with smearing. My suspicion is that the older tubes just can't handle the ZOTL/R10 power demands.” –Hirsch
● “VT-231 Ken-Rad, flat black plates - Great Bass, drive, sweet midrange (maybe not as sweet as the Syl VT231). Great top end extension as well and not harsh.” –scottpaul_iu
● “This is a tube that I enjoy immensely. Bass is very propulsive and visceral and grabs you at first listen. Unexpectedly, low level detail is best of all the tubes tested so far. I had my sister randomly switch tubes while I was blinded and I confirmed, in my setup at least, that this tube is the best for low level detail. Midrange is slightly less sweet than the 1952 syl 6SN7GT. Bass slam on this tube has to be heard to be believed. Instrument separation is slightly less than the Raytheon vt231. Vocals are a nice blend of clear and sweet on this tube. A very quick tube, outdone only by the 1952.” –adhoc
● “With reference to the KenRad, the first version can have either black glass or clear glass, always with staggered plates (I was the one who coined the 'staggered plates' moniker - there is zero sonic difference between the two). In the late 40's, when GE had taken more control over the KenRad operation, there was a second version with clear glass and in-line ribbed plates - it is NOTEABLY inferior sonically - gone is the big bass and the midrange bloom, added is a dry, slightly constricted sound with no magic.” -Robert H. (in personal correspondence)

National Union “VT-231” [PHOTO HERE]
[grey/black glass (former rarer) - black glass starting 1/4 of way from top of base and ending near top, black base, circular top mica with 2 rectangular mica pieces attached to sides, copper grid posts,]
● “NU never actually made a tube designated VT-231, although some have the JAN-CNU designation - the earlier grey glass model. It sounds very different from the later black glass version that was manufactured from about 1949 to 1953 and NEVER had a military designation.” Robert H. (in personal correspondence)
● “Good drive and great midrange, softer bass and a touch euphonic” –Chimera
● “The NU tubes are both some of the smoothest 6SN7s I've heard. They aren't really lush so much as they are "liquid." RCAs are definitely sweeter. I prefer the gray glass for its tonality, but the black glass has better bass in my system” –Len
● “…the sound is very good. Wide soundstage, a little more forward presentation, very good bass, and treble, and a sweeter midrange than the Kenrad. I still like the way the Kenrad attacks better. but if your looking for a lusher sounding tube than the KenRad theses grey glass NU are good. They dont sacrifice the bass and little treble.” –tom hankins
● “I agree completely with Tom about the grey glass NU tube. The lushness he describes doesn't seem to apply to the black glass version, but that tube has its own strengths. Both are worth trying if you can find them.” –Hirsch
● “The NU black glass is very similar to the KenRad, the bass is not quite as huge. A bit dark, beautiful sound.” –Robert H

Raytheon VT-231 (2 versions, T plates and flat plates - former is of earlier construction than the latter) [PHOTO HERE]
[2 versions - both clear glass, black base, but one (later version) has 2 free support posts and flat plates, other does not (has normal T-plates)]
● “Like the Tung-Sol a little sweeter, nice balance of detail and timbre” –Chimera [flat plates]
● “I thought it had a hard area in the midrange that gave the Sylvania a clear edge. I was wrong, I think. I've now tried two sets in the past week, and there's no trace of the hardness I heard before. My suspicion is that the amp had not fully burned in when I tried them, and that what I was hearing wasn't the tubes, but the amp itself. It's also possible that it was a cabling or source issue, since there have been a lot of system changes since the early tuberolling attempts. Right now, these tubes are heaven. Extended highs, a crystal clear midrange lacking some of the Sylvania's warmth, and an extended bass response. Interesting, actually, since these were also the tubes I eventually settled on with the MicroZOTL when I had one. They've got something that eventually brings me back to them. The level of detail seems higher than it is with Sylvania's, and the bass impact of these tubes really comes through on the R10.” –Hirsch [flat plates]
● “Raytheon VT-231 or JAN-CRP-6SN7GT are much more forward in their presentation. [compared to Ken-Rad and Sylvania VT-231 combo]” –Glod [flat plates]
● “If you like (much) more excitement and drive; change the Sylvania's for Raytheon JAN-CRP-6SN7WGT from the early to mid 1950.” –Glod [flat plates]
● “I like this tube. It doesn't compare to the better 40's 6SN7, but it's significantly cheaper (or at least it should be). It's relatively linear with a little emphasis in the midband. Not a big sound, but very easy to listen to.” –Len [flat plates]
● “excellent dynamics. Loads of power, but can be slightly harsher than the other two pairs [syl vt-231 and ken rad vt-231].” –Hirsch, in personal correspondence with author [flat plates]
● “I've been experimenting with the Raytheon VT-231. There are two versions of this tube. One is a box plate, that looks like the early Sylvania plates. I wasn't particularly impressed by this. It's a good tube, but doesn't have anything the other 6SN7's I've been using couldn't do. However, the other version has flat plates and support rods. This is a different beast entirely. It's got a very fast attack, with extreme control of the lower midrange and midbass. Extended highs. The midrange is not as lush as some of the other 6SN7's, but it's dead accurate. In front of a pair of Syl VT-231's, this tube makes the Supra a very forward sounding amp, with great speed and the best bass I've gotten out of the amp. Since I put it in a few weeks ago, I've simply left it there, and listened to music (no urge to roll any more tubes right now).” –Hirsch
● “Compared to 1952 Syl 6SN7GT and KenRad vt231, this is a brighter sounding tube. There is a certain forcefulness to the presentation that is quite attention-grabbing. Vocals are extremely clear with this tube. The mids are less sweet and a wee bit thinner than both the KR and 1952. There is a slight dry-ness to the sound overall. Clarity clarity clarity, yet less low level detail than the KR. A tad less bass slam than the 1952. I noticed some reverb.” –adhoc
● “There are at least FOUR versions that I have found. This tube, in one form or another, was in production from 1943 to at least 1956 - a long time. There is a short bottle T-plate version and a tall bottle version with narrow plates. Number of support rods and clips on the micas differed. Other minor changes. Most prefer the ribbed plates over the T-plates and the earlier ones are better.” –Robert H. (in personal correspondence)

RCA VT-231 [PHOTO HERE]
[black base, grey/black glass (latter far more rare), 2 extra rectangular mica pieces attached to either side of round top mica, grey glass starts from the bottom and ends near the top and will have a few thin clear vertical lines 'scratched' into it by both extra mica pieces, crimped filament openings]
● “RCA VT-231 grey-bottles are much warmer and have a grand presentation with accentuated reverb. [compared to Ken-Rad and Sylvania VT-231 combo]” –Glod
● “I have used the gray glass RCA VT231 as input in the MPX3 (7 months ago) and it had good bass and nice detail,(sorry to be so vague but I haven't used them for a while) but it doesn't sound 'right' as a TS RP does.” –Rob N
● “I had tried the RCA VT-231, and thought the high end didn't cut it compared to Sylvania's.” –Hirsch
● "As far as lushness goes the 1940's RCA grey glass is the one to go for." -RobN [in personal correspondence with author]
● “The warmest, best tonally is the early grey glass RCA VT-231. This one has very strong bass, a bit less defined, but an incredible rich midrange.” –Robert H
● “Yes, the RCA VT-231 is a bit syrupy. It certainly doesn't have the openess and detail of, say, the Sylvania VT-231. But it's TONALITY is just, well...right. The sound of musical instruments - their tonality - is simply the correct one. I just love this tube. So musical. It's sorta like a real babe, with killer knockers, but she's got a little too much around the middle. You know there's something not perfect, BUT - it just feels so damn good you can't keep yourself from going back.” –Robert H
● “Here we get into murky territory. RCA produced a grey glass 6SN7GT with side micas straight through from 1942 until at least 1956, and there is a great deal of sonic variation among tubes within that period. None are bad. But the early one sound far better. This is one of my favorite 6SN7's, but let's face it - it is very warm and lush, has a huge soundstage and huge bloom - not for Cary owners (for example) whose amps are already tubby sounding. In a good, neutral tube amp - which is what a good tube amp is, actually - this tube is a king. But be VERY careful about the vintage. Early ones have the magic. Later ones are good but no moondust.” –Robert H. (in personal correspondence)

Sylvania VT-231 [PHOTO HERE]
[black base, white (1940s) or green (1950s - very rare) labels, bottom getter (visible), black T-plates, tall bottles, rectangular top and bottom micas]
● “Wide bandwidth, well balanced, excellent sound stage and air” -Chimera
● “Good high end extension, a warm and full midrange and decent bass extension. Imaging is precise and the perceived staging is wide. What could be better?” –Hirsch (refers to 1940s and pre-1953 construction tubes only)
● “Right off the bat, the bass is recessed but with more control. Everything sounds more refined and delicate. Soundstage is bigger too. Will report back once they are burn in.” -Habib
● “I've been using all 3 Sylvania VT-231s in my MPX3 for the past couple days now. While the clarity and resolution improved, bass didn't. I would describe the overal sound characteristic as neutral, transparent, and musical. Problem right now is with the Sylvanias, the MPX3 is great for jazz and classical but not so great for hiphop and rock. I am wondering if TS as gain tube will take care of my problem. Just something to make it bring out more of the bass.” –Habib
● “Turns out that the bass is not so much recessed but the overall sound being more neutral. I was used to the stock EH tubes being more boomy.” –Habib
● “Sylvania VT-231s are good value tubes, with the main deficiency in the bass region. Some here think it's a sweet tube; I disagree. It's a very linear tube from the midrange on up and does the treble region very well (extended and grainless).” –Len
● “Very nice midrange, slightly weak bass, good highs. One of the best all-around tubes. This is not the 1952 "big bass" tube, which is not a VT-231. IThe 1952 tube looks similar, but has green print, and will say 6SN7GT on it. There will be a three digit date code on the base of the tube, and the first number will be "2"” –Hirsch, in personal correspondence with author
● “this tube afforded great improvements in midrange,vocals and detail.bass was not as tight as the Ken-Rad but the vocal performance was superior.this tube was fond of piano jazz and lush vocal tracks.It also matched well with all the output tubes and ran a little hot.” –Tuberoller
● “Using the Sylvania VT-231, I simply couldn't get a decent bass response, no matter what I did.” –Hirsch
● “VT-231 Sylvania, black plates, wide bandwidth, well balanced, excellent sound stage and air, good bass but not quite as much bass as the KenRad VT231.” –scottpaul_iu
● “If you are looking for strong bass, avoid the mid-40's Sylvania VT-231 which has weak bass” –Robert H
● “Curiously, in your pictures you show a version that is neither of these - you show the first version from 1943 that has a plate getter and engraved base - it is perhaps the best of any, it actually has bass! Along with the other characteristics of the 1945 white label version. Worth checking around for, a very good tube, best Syl VT-231 IMO.” –Robert H. (in personal correspondence)

Tung-Sol VT-231 [PHOTO HERE]
[keyhole-shaped black plates, black glass ending 1/4 from top, black base, oval or round (rare) micas]
● “Tung-Sol round-plates are much faster, open and perhaps a bit colder [compared to Ken-Rad and Sylvania VT-231 combo]” –Glod
● “I really like the Tung Sol VT 231.It has a very,very nice overall balance and is fast and accurate.Not the killer bass of the Ken Rad and not the super lush midrange of the CBS brown base but a nice sonic signature that will not offend.” –Tuberoller
● “This tube was never considered special until some dealer got a bunch, noticed the price creeping up, slipped a few judicious posts onto Audio Asylum shilllling them, and sat back to watch he demand he generated drive up the price - and then, it snowballs - everyone's gotta try them - and then, everybody who paid $250 to $300 for a pair of tubes all of a sudden starts hearing incredible things in them and they are the new "best". One idiot on Ebay has even taken to selling French Neotron round plates and alluding to them being as good as Tungsols, or maybe even made by Tungsol! (hint - the Neotron is an OK tube, but nothing special.) The fact is, the T-S round plates are very fine, have great inner transparency and are unique sounding, the mids are not lush, but they do have a nice touch of euphonics, the bass is weaker than I would like and the highs can be sibilant - a problem. It does have the virtue of being the most uniformly quiet 6SN7 and consistent from sample to sample.” –Robert H. (in personal correspondence)



- 2. NOS TUBES

Amperex 6SN7GT [PHOTO HERE]
[red labels, grey T-plates, rectangular top & bottom mica, ‘flying-saucer’ getter holder at bottom]
This tube was never made by Amperex. ALL Amperex tubes on the market are Russian relabels. The Ameperex tube looked suspiciously like a Sovtek, right down to the 'flying saucer' getter. Amperex catalogs have been checked and verified to prove that Amperex never made a 6SN7 tube. For all you that have paid big $$$ for Amperex 6SN7GTs:

Brimar CV1988 6SN7GTY [PHOTO HERE]
[dark brown base, black glass (starting 1/4 from base and covering top of glass) with white labels on glass, clear glass (very rare)]
● “FE is Brimar's manufacturing code, and the Y in 6SN7GTY simply means it has a brown micanol base. It's a good, lush sounding tube and perfectly usable in your amp.” –Len
● “The Brimar CV1988 6SN7GTY was the first 6SN7 I fell in love with, so it does have a place in my heart. It is not a TS/RP-sounding tube, however. Brimars are very sweet, lush sounding tubes. […] It should be noted that Brimars are also the quietest 6SN7s I've ever had the pleasure of using. All in all, the CV1988 is a terrific tube, but it is not a TS/RP competitor. You turn to Brimars when you want a more euphonic sound.” –Len
● "Lush and romantic = Brimar or RCA, Brimar being more lush but some consider bloomy. Both have strong lower end." -Len [in personal correspondence with author]

CBS/Hytron 6SN7GT [PHOTO HERE]
[black plates, black base, white labels, bottom getter (not usually visible)]
● “Quiet and musical, the best of the non-military tubes” -Chimera
● “The Hytrons are the most mellow and have the most refined sound. Very smooth and airy up and down with a nicely detailed high end. Not much punch. Never gets bright. Bass is there, but not very detailed and tubby sounding.” -bobjew
● “The Hytron and slightly later CBS-Hytron 6SN7GT is an excellent sounding tube that can be found from time to time on Ebay for a very reasonable price. Good extension top to bottom, a lucid midrange, smooth, doesn't call any attention to itself in the audiophile sound effects department.” –Robert H

CBS/Hytron 6SN7GTB [PHOTO HERE]
[black bases, red labels, side getter]
These tubes are rebranded GE 6SN7GTB tubes.

GE 6SN7GTA [PHOTO HERE]
[side getter, grey plates, black base, white labels, round top mica]
● “The great driver tube? Fast, wide bandwidth, smooth sound at the expense of the of low level detail. Along with the Sylvania yellow Labels and Tung-Sol Top getter 6SN7GTB, a great “fourth” tube in Atma-Sphere amps.” -Chimera

GE 6SN7GTB [PHOTO HERE]
[gray plates, side getters, black base, white or orange labels] [4 vintages: a. early 1950's (D-getter, white labels) b. early 1960's (O-getter) c. mid-1960's (exposed top filament wire) and d. 1970's (coin base)]
● “Work horse, lacks refinement, a good tube” -Chimera
● “EARLY 1950s: Not a bad tube, not a great tube. Very warm, not harsh, warm but not overly ripe or detailed mids, a bit zippy on top, not magical, but overall, a pretty decent tube. This version appears to have been made up to the early 1960's, but sonically the tube declines as the dates get more recent. Look for early 50's dates.” –Robert H
● “EARLY 1960s: Again, not terrible, but not as good as the earlier one, a bit more grain & grit, and the bass is bloated & indistinct. There are worse, but this one is nothing to go out of your way for.” –Robert H
● “MID-1960s EXPOSED FILAMENT WIRE: This one has the filament wire running across the top-mica between the cathodes, giving a nice lighting effect - but sonically, it's not very good - dry, grainy, zippy highs, a flat, uninvolving sound. Nice light effect though.” –Robert H
● “1970s COIN BASE: Horrible, microphonic, noisy, unmusical, one of the worst 6SN7s ever made.” –Robert H

Ken-Rad 6SN7GT
[usually JAN versions, black base, clear glass, staggered plates - IDENTICAL TO VT231 AFAIK]
● “Bass a little tubby, but clean with great ambiance and air” -Chimera

Raytheon 6SN7WGT
[brown base, red labels, top getter with rectangular getter holder on stalk, black plates with 'cubes' on top mica, round top mica with 3 'umbrella spokes']
● “A few other suggestions are the Raytheon 1950's 6SN7WGT brown base, has great bass and nice warmth (can have yellow, orange, red, brown printing depending on the year)” –Robert H

RCA Silver Label 6SN7GT / GTA / GTB [PHOTO HERE]
[black plates, bottom getter (usually not visible), black base, silver labels]
● “More musical than the Sylvania Chrome Domes, rich harmonic structure with excellent imaging and sweet non fatiguing sound performance. Good imaging and low level detail resolution. Becomes a little too sweet in equipment that uses a lot of 6SN7 types. Nice combination with Sylvania Chrome Domes and the better 6SN7 “driver” tubes.” -Chimera
“The 1950's GT is a completely different animal than the RCA GTA or GTB from that period, in fact, it's pretty much the same tube as the 40's grey glass - not as good as I mention above - but still a nice tube. The GTA came in two variants - the single side getter and double side getter. Both lack the ultimate refinement but are good, punchy musical tubes. Fun tubes. The GTB's are not the worst GTB's, but not really worth picking up for a serious 6SN7 -phile.” –Robert H. (in personal correspondence)
”
RCA Silver Label 6SN7GT / GTA / GTB [PHOTO HERE]
[black plates, single/twin side getters, black base, silver labels]
● “What to get when you combine the bandwidth and speed of the Sylvania Chrome Dome and rich harmonic structure of the RCA silver Labels Bottom Getter….the RCA Silver Labels Side Getters. But the highs are a little recessed and the bass is a little forward. Low level midrange resolution a little obscured. Overall a very nice tube.” -Chimera

RCA Orange Label 6SN7GTB [PHOTO HERE]
[bottom getter (usually not visible), orange labels]
● “Rich midrange, warm sound, likes being combined with other 6SN7 types, likes the Atma-Spheres” –Chimera

RCA 6SN7WGT
[???]
● “I am also liking the RCA 6SN7WGT.This tube has a lush midrange with very extended treble and good bass.I love this one for most Jazz music with the Beyer 931 phones.” –Tuberoller
● “Never existed. Sometimes in the late 60's you see some tubes labelled as such due to the chaotic nature of 60's labelling, but RCA never made 'em. RCA DID make a very rare 6SN7GTY in the 50's which is a grey bottle tube and very nice, pretty much the grey glass 6SN7GT of the period with a brown base.” –Robert H. (in personal correspondence)

Sylvania 6SN7GT (1952 vintage ONLY) [PHOTO HERE]
[3 holes in each plate, copper grid posts, bottom getter, green labels, black base and plates, vertical date code (read from top-down) ‘2xx’ with ‘xx’ representing week #, 'polished' silvery rectangular mica]
[NON-1952 vintage short-bottle 6SN7GTs can have ROUND MICAS and NEVER have 3 holes per plate [only 2] - check for an example in my photo gallery]
● “One tube that you should look out for is 1952 Sylvania 6SN7GT. It's constructed with the same tooling as the 40's VT-231, but this tube is different in that it actually has good, propulsive base. I can only speculate why it sounds much better even though the tooling is the same. But it is certainly one of the top 5 6SN7s on my list. For a while, I thought all these Syl rectangular plated 6SN7GT were all the same, but it turns out my previous 1952's were on their last legs.” –Len
● “The best treble I've heard is the 1952 Sylvania 6SN7GT "Bad Boys" (I refer to these tubes as Syl VT-231s on steroids - better treble and rock solid bass). The first time I heard the 52's, I literally had an "oh my!" reaction to the treble.” –Len
● “The 1952 Sylvania 6SN7GT shares the sonic characteristic of the previous 6SN7GT/VT-231 tall bottle, except many say it is more refined and has significantly more (clean) bass.” –Len [in personal correspondence with author]
● “A tube with what is imo a slightly dark and effortlessly natural sound. An extremely sweet (but not overdone) midrange. There is roughly the same amount of slam as the Ken-Rad VT-231 [KR], yet the slam is definitely less visceral than the KR. This is an extremely musical tube, with a less airy sound than both the KR and Raytheon [RT]. The treble on this tube is more ‘tubey’ sounding, and is less cold than the KR and certainly the RT. What surprised me was that there was slightly less discernable low level detail than the KR. Low level detail is the same as the RT. Instrument separation was slightly less than the RT. A completely non-fatiguing tube to listen to. Female vocals are a joy to listen to on this tube – echoing another member, I really feel like reaching across and getting to know Diana Krall a –whole- lot better with this tube.

” –adhoc
● “If you can, try the Sylvania JAN-CHS-6SN7GT from 1952, bottom getter - incredible bass, warm lovely mids and very extended sweet highs. Some days I think this may be the best sounding 6SN7 ever made.” –Robert H
● “The '52 Syl came to me from Neville in Australia who had a big stash and I first posted about them on Tubes Asylum and coined the "Bad Boys" moniker that still sticks. Your description is dead on, later in '52 the tube changed to a shorter bottle with round serrated micas - an ordinary, dry sounding tube - but it does have a 1952 date code and many sellers try to pass it off as the good ones. All around this is one of the best 6SN7's ever made.” –Robert H. (in personal correspondence)

Sylvania 6SN7GT / WGT / GTA / WGTA / GTB (1950s vintage) [PHOTO HERE]
[“Chrome Dome” / “Silver Top” (ie top getter), black base, green labels, 'Sylvania' text is in 'bold'-looking font]
● “Non-fatiguing, smooth, with good detail resolution, bandwidth and speed. Bass can be a bit warm and exaggerated, a good thing if your speakers are bass shy. Does not have the midrange ambience and resolution of the VT-231 types. But very good overall.” –Chimera
● “Good high end extension, a warm and full midrange and decent bass extension. Imaging is precise and the perceived staging is wide. What could be better?” –Hirsch (refers to 1940s and pre-1953 construction tubes only)
● “I've tried the 6SN7WGTA. They tend to have a very dry sound. Midrange is lean. Extension at highs and lows is pretty good. The exact sound may depend on year of manufacture. I had a set from 1952 that I used regularly when I had the ZOTL, but later years exacerbated the issue with dryness of the sound. I heard the same dryness with the Supra, and didn't explore these tubes much further. They can be a decent tube, and might work well as output tubes if a tube with a full midrange was used as the gain tube.” –Hirsch
● “Another tube that I didn't really like with the R10, but am enjoying a lot with the PS-1 is the Syl 6SN7WGT (brown base). Clean and dynamic. In some amps, with some headphones, these tubes can sound dry in the midrange. However, the PS-1 seems to handle them well.” –Hirsch
● “Another good tube by Sylvania, but the price of these are climbing beyond what I'd pay for them. If you can get them cheap, they're definitely worth an audition. Presentation is big and strong, particularly in the bass region. Top is a little sibilant, but not terribly so. [refers to WGT brown base]” –Len
● “IME the 6SN7WGT is a very fast tube with great highs and tight lows. However, I've found a dryness in the mids that was sometimes too dry, and I've never kept them in an amp for very long. A good tube that hasn't been to my taste. A friend of mine loves them as output tubes when using his maxed-out PPX-6SN7 with the PS-1, so I'm probably going to revisit them soon. [refers to WGT brown base]” –Hirsch
● “The 6SN7WGT and WGTA (sounds very similar) are good tubes, but they aren't on par with the earlier 6SN7W tubes (any of the three versions). It is the midrange that is lacking: a bit lean and diffuse compared to the full sound of the 6SN7W. The treble isn't as sparkling either, although the 6SN7WGT is still great in the upper registers. I actually like the midbass of the WGT/WGTA better though, as I find it a little tighter. But overall, it doesn't compare to the terrific Syl 6SN7W.” –Len
● “this tube offered much wider soundstage and sweetened the midrange nicely. It did nothing to improve the bass, which remained thin and sloppy. [refers to Syl 6SN7GTA]” –Tuberoller
● “6SN7GT, Sylvania Green Label, nice even sound, not harsh, smooth, with good detail resolution and bandwidth extension.” –scottpaul_iu
● “6SN7GTB, Sylvania Green Label, rich harmonic structure, good midrange, decent soundstage. This would be a good NOS tube to get as they are fairly easy to find and not to pricey right now.” –scottpaul_iu
● “6SN7WGT, Sylvania Green Label, Top Getter, “silver top” , very clean sound with great detail resolution and speed. Bass can be a little tubby and not well resolved and midrange a little congested.” –scottpaul_iu
● “6SN7WGTA, Sylvania black base green label, clean and fast with great drive, good bass.” –scottpaul_iu
● “The WGT and WGTA versions possess the Sylvania trademark sound, but they are not as airy, are more aggressive sounding, but has a slightly thinner mid and highs. [when compared to the 1952 Syl 6SN7GT]” –Len [in personal correspondence with author]
● “First - there is only ONE Chrome-dome. That is a 1950's 6SN7GT with mid-sized bottle that has the getter almost entirely covering the glass, hence the term 'chrome-dome' was coined to describe it. It is a fabulous sounding tube, close to as good as the '52 Syl, but extremely rare as it had such an awesome rep early on in the tube renaissance that it is pretty much long been absorbed into private collection where very few pop out. Unfortunately, due to the legendary status of the real chrome dome and it's virtual disappearance from the market, sellers have been calling virtually any top getter Sylvania by that name - despite those tubes not having a real chrome-dome at all. There are a few versions of the WGT, and the WGTA has etched markings on tyhe glass. The GTA came in two versions during the 50's with different plates, one hugely good sounding, the other not so great. There are numerous GTB's that range in sound from ok to not so great, but the GTB has nothing to do sonically with the others, and really aren't worth seeking out.” –Robert H. (in personal correspondence)

Sylvania Yellow Label 6SN7GTB (1960s vintage) [PHOTO HERE]
[black plates, top small getter, yellow labels, black base]
● “Clean sound with good harmonic structure, excellent midrange and bass, high frequency a bit recessed and nice soundstage and ambience. Very good driver tube.” –Chimera
● “I've seen the Gold (yellow) lettering on the Syl 6SN7GTB. It's a tube that has good tonal balance, but IMO doesn't reach the same level of detail as the 6SN7GT.” –Hirsch
● “Syl 6SN7GTBs are from the 60's and come in several iterations. IME, it's a good value tube with lots of slam, but lacks the refinement of the earlier tubes. While the resolution is good, it just doesn't demonstrate the finesse of 1940's tubes. Hear a TS RP and you'll know what I'm talking about Most GTBs had similar characteristics.” –Len
● "Surprisingly refined sounding - not bad considering the bargain prices these can be picked up for. Great detail and air. Cymbals have a very nice shimmer to them with this tube. Very very slightly dry sounding. Not too much impact. Bass seems a tad moderated with this tube compared to, say, a Ken Rad vt231. Great extended decay on notes. Laid-back sounding." -adhoc

Sylvania 6SN7W [PHOTO HERE]
[black plates, top getter, metal (with black/green labels) OR black bases (with green/white labels), tall (metal and plastic bases) or short bottles (plastic only bases)]
● “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 plates structure. The smaller one has better low level detail and the larger ones have more slam.” – Chimera
● “Sylvania 6SN7W short-bottle are similar to the Tung-Sol RP, but more forceful in their presentation” –Glod
● “Syl 6SN7W tall bottles, especially the metal base, are always more microphonic (not to mention less reliable). Before you think I don't like these Sylvanias, let me say their sound is huge and gorgeous. I don't find them dark at all, but rather very lively, forward, and big sounding. If only they were less microphonic and less resistant to arc-over (I hate it when $100+ tubes die prematurely), I'd have no reservations recommending this tube if you need to liven up your system. IME, the 6SN7A and 6SN7W metal base are the same exact tubes. Construction is identical and sound is the same to me .... just print differences at the very top of the tube.” –Len
● “The Syl 6SN7W tall bottles - both metal and black base - throw a huge soundscape with lots of heft and slam.” –Len
● “Hirch's opinion of these tubes probably differ from mine, but this is what I think of the Syl 6SN7W metal bases: It's a big big sounding tube that throws the most expansive soundstage of any 6SN7. Good bass, lush mids, very extended treble. They really do add a "sparkle" to the highs that is unlike any other 6SN7. Problem for me is this sparkle gets fatiguing after a while. Triangles and high hats that were initially amazing get a bit grating. The big, lush sound is also a double edged sword, and I often find myself preferring the finesse of other tubes like the TS RP. Syl 6SN7W metal is an exciting tube, no doubt. It's just a little too much for me. I do encourage people give it a shot if their wallets are deep enough (obtain it soon as prices aren't getting any cheaper). My personal preference is just that - personal; I'm sure this tube will captivate a great many other listeners.” –Len
● "Sylvania 6SN7W has strong bass and is full, but I wouldn't say it's romantic or warm (though it is very musical IMO)." -Len [in personal correspondence with author]
● "The Syl. 6SN7W metal can have an amazing soundstage but also can be prone to a little harshness in the higher frequencies." -RobN [in personal correspondence with author]
● “The W metal base is full, big sounding, euphonic, very magical - if you get the right pair. They are more problematic than any other 6SN7, can arc over easily, can be very microphonic, and the risks are as high as the price. When they are used and drop in transconductance by about 20%, they sound dull. Magic is gone.” –Robert H

Telefunken 6SN7GTA [PHOTO HERE]
[GT: ??? GTA: top getter, white labels on glass, black base, round mica with diamond points scattered around it]
GT: This tube certainly lives up to its ‘legendary’ status. Why? Because it never existed. 6SN7s were NEVER made by Telefunken.
This tube is always sourced from Philips Holland (which in turn sourced from 1960s East German or Russian factories) Also occasionally rebranded as Ultron and Hoges.
GTA: This tube, while labelled ‘Made in West Germany’, was almost certainly not made in West Germany. Most who purchase this tube have been disappointed with its sound, describing it as ‘boring’ and ‘dry’ (AA).

Tung-Sol 6SN7GT 'Round Plate' [PHOTO HERE]
[round mica [?-1942] or oval mica [1942-46] (no audible difference), 2 U-shaped structures on mica, thin keyhole shaped plates, mostly with dark glass, silver labels]
● “Tung Sol round plate 6SN7GT: what can I say? This tube in front of a pair of Sylvania's seems to do it all. Exquisite detail, strong bass, glorious midrange and extended highs.” –Hirsch
● “Those are the best of the Tung Sol's. A stunning tube. Highly detailed, full midrange with superb bass.” -Hirsch
● “If you like more speed and agility, change the Ken Rad for a Tung-Sol 6SN7GT (round-plates)” –Glod
● “I keep hearing TS RP are microphonic, but of the dozen or so pairs I've owned, that's never proven the case.” –Len
● “TS RP are my favorite 6SN7s, bar none. They do everything right, and the only complaint I hear about them (other then microphonics which is contrary to my experience) is that they are linear to the point of being boring If you're using a SET, nothing expresses their midrange beauty like a TS RP.” –Len
● “I think I prefer the TS RP which IMO sound 'lusher' than the 6SN7W metals [metal bases]” –Rob N
● “The TS RP, on the other hand, doesn't possess as large a presentation [as the Syl 6SN7W] but is a lot more refined and seductive.” –Len
● “I try not to use the soundstage word when talking about headphones but using the TS RP is presenting a not only wider but deeper and much clearer soundstage with the senns. than either the Sylvania VT-231 or the KenRad VT-231. I still think the bass is more pronounced with the KenRad, but the more I use the TS I'm starting to think the bass is better defined through them.(the TS) The midrange and treble is by far the best I've heard through my system. So sweet, smooth, and still with great detail.” –tom hankins
● “TS RP simply has the best separation of space - with accurate timber and timing. The midrange is magical, especially when mated with SETs [Single-Ended Triodes].” –Len
● “The most musical tube is the Tung Sol round plate. It's simply the best balance of everything a tube can offer IMHO." -Len [in personal correspondence with author]
● "This tube seems to have a slightly dry signature when compared directly to the Syl '52. It seems to combine the best traits of many tubes - the bass and impact of the KR VT231, the clarity of the RT VT231 and most of the musicality of the Syl '52 with unparalled detail. This tube makes music, any music, beautiful to listen to - it certainly lives up to its reputation." -adhoc

Tung-Sol White Label 6SN7GT (1940-50s vintage) [PHOTO HERE]
[made between 1948 and 1956. structure is completely different from the abovementioned Round Plate GTs - these have grey 'T'-plates and a bottom getter. rectangular getter holder. tall bottle with black bases and white labels. these resemble GTBs (the next tube below) except for the bottom getter.]
● “Concurrently with the last days of the TS R-P there was a version with regular ribbed plates - that could have been grey OR black, and has the notorious round side mica spacers termed "mouse ears". A very, very good sounding tube. There was a later version that squared ofc those ears - still the same tube, then they dropped the ears all together and the plates were always grey - still a super sounding tube. But it's not commonly found, and unless it has the mouse ears, people often mistake it for Russian - good for me, I love the tube and pick 'em up at dirrt cheap prices and get better performance that most of the big buck stuff.” –Robert H. (in personal correspondence)

Tung-Sol White Label 6SN7GTB (1960s vintage) [PHOTO HERE]
[3 versions: a. top D-getter, tall bottle b. top O-getter, tall bottle c. short bottle. ALL VERSIONS have triangular black plates, black base, white labels.] [There are also a number of Tungsol branded GTB's with flat ribbed plates that are rebrands from other makers, particularly RCA. All Tungsol GTB's after the tri-plate short bottle version are rebrands of inferior quality.]
● “Very fast, clean and dynamic. Excellent bandwidth, good harmonic structure. A little too analytical and it sounds better mixed with some of the more musical tubes Very good driver tube and likes to be mixed with RCA bottom getter 6SN7.” -Chimera
● “The GTBs are more dry in the upper registers and lack the refined, airy, grainless mids and highs of the earlier round plates. Bass is pretty solid and controlled.” –Len
● “The Tung Sol 6SN7GTB is a nice tube. Good clear sound.” –Hirsch
● “The first version - tri-plate/D-getter tall bottle - was actually the same tube as the identically constructed WGT and WGTA, I have seen them mixed together in a factory bulk pack with identical date & batch codes - so they are all the same tube. Bonus, because it's a very nice sounding tube and because some unknowledgeable people look down on GTB's, they are easier to find & less expensive. Well balanced, rounded tone, reasonably good and tight bass, the highs are smooth and not excessively bright. A good all round tube.” –Robert H
● “Next was a version, also with tall bottle, but with O-getter - I find this one to sound virtually the same as the D-getter version, there may be some slight sonic differences for the obsessive types with too much time on their hands. Personally, I would rather listen to the music than worry about micro-differences of this magnitude. They are cheaper yet and a good buy.” –Robert H
● “Short bottle, tri-plate, early 1960's. Similar sonically to the earlier ones, a bit less open, still a very good tube.” –Robert H
● “But here's an inside tip - Tungsol late 50's and early 60's 6SN7GTB are exactly the same as the WGT and WGTA, except they have a black base - and nobody wants GTB's, so they usually go cheap. They are exactly the same tube, Tungsol simply relabelled WGT's as GTB's to fill GTB orders. I know this, I've had a bulk factory box that had tubes with the exact same date and batch codes - but were labelled either WGT, GTB, WGTA, or even just GT. All identical and come from the same production run. If you see some Tungsol GTB's, and CBS/Hytron 6SN7GT's, grab some, they are still an excellent value.” –Robert H

Tung-Sol 6SN7WGT [PHOTO HERE]
[black plates, brown base, top getter]
● “Sounds similar to the Tung-Sol VT-231, but not as clean” -Chimera
● “But here's an inside tip - Tungsol late 50's and early 60's 6SN7GTB are exactly the same as the WGT and WGTA, except they have a black base - and nobody wants GTB's, so they usually go cheap. They are exactly the same tube, Tungsol simply relabelled WGT's as GTB's to fill GTB orders. I know this, I've had a bulk factory box that had tubes with the exact same date and batch codes - but were labelled either WGT, GTB, WGTA, or even just GT. All identical and come from the same production run. If you see some Tungsol GTB's, and CBS/Hytron 6SN7GT's, grab some, they are still an excellent value.” –Robert H

Tung-Sol 6SN7WGTA [PHOTO HERE]
['triangular' black plates, brown base, white labels, tall bottle, top getter]
● “Very good bandwidth, bass, detail and soundstage” -Chimera
● “But here's an inside tip - Tungsol late 50's and early 60's 6SN7GTB are exactly the same as the WGT and WGTA, except they have a black base - and nobody wants GTB's, so they usually go cheap. They are exactly the same tube, Tungsol simply relabelled WGT's as GTB's to fill GTB orders. I know this, I've had a bulk factory box that had tubes with the exact same date and batch codes - but were labelled either WGT, GTB, WGTA, or even just GT. All identical and come from the same production run. If you see some Tungsol GTB's, and CBS/Hytron 6SN7GT's, grab some, they are still an excellent value.” –Robert H



- 3. NEW STOCK TUBES

NEW STOCK – Electro-Harmonix EH6SN7 [PHOTO HERE]
[black plates, black base, black labels on glass, top getter]
● “The Electro Harmonix were the most dynamic in the MPX3 . The Bass is also the best and biggest of the three; quite detailed and tight. Midrange is also full of detail air and transparency up and down the range. Gets a little too bright in my system at times, but generally the most fun and involving tubes to listen to so far for me.” –bobjew
● “With the Electro Harmonix 6SN7's in current production, there is no need to suffer.” –Hirsch
● “They are fast-paced tubes with a bit of a heavy bass and paired with a slower driver tube the combo sounds quite nice.” –donovansmith
● “I came across a new 6SN7 tube by Electro-Harmonix and it sounds great. This tube seems to be a very good copy of the Sylvania VT231.It has killer bass and an excellent midrange and vocal performance. It warms up quickly and is not noisy or microphonic at all. It is an excellent value at $10.00 a pop. […] The build quality is high and they are very, very closely matched as tested on my tube tester. These get a "best buy" recommendation from Tuberoller. Try them before dropping big bucks on the Ken-Rads or CBS Brown or Red based tubes.” –Tuberoller
● “The biggest finding is that the Electro-Harmonix 6SN7 tube is about as good as a Syl 6SN7GTB.” –scottpaul_iu

NEW STOCK – Electro-Harmonix EH6SN7 Gold Pins [PHOTO HERE]
[gold pins, brown base, otherwise identical to non-gold pin version]
● “Aside from the obvious differences between the tubes– gold plated pins and the new goldish colored base; they look exactly the same. The model number is the same. The box has the same graphics with the addition of "gold pin" and printed in gold instead of black. Not surprisingly, they also sound very similar.” –bobjew

NEW STOCK - Sovtek 6SN7 [PHOTO HERE]
[black base, black labels on glass, bottom getter (not usually visible) with 'flaying saucer' getter holder] [known to be relabelled amperex (with brown bases)]
● “First off, forget about the Sovtek 6NS7's as they sound really lousy. I was at the electronics store for something else and they just happened to have a stock of them for 5.00 each and thought I'd give them a try. The sound was flaccid and weak compared to any of the others. Weak Bass and very little HF air. Tried one of these as the driver in combination with the others and their sound was diminished.” -bobjew
● This tube has an extremely forward and big bass, a moderate amount of slam, a too-rich sounding midrange and slightly recessed highs. Mids are a bit shouty-sounding. Where this tube fails, and fails miserably, is details and separation. When compared to the Syl 1952 6SN7GT / KenRad vt231 / Raytheon vt231, everything seems hopelessly smeared. There is less 'air' around instruments than both the 1952 and RT.” –adhoc



- 4. 5692 TYPE TUBES

An interesting anecdote: the 5692 type tube was first developed by RCA (but RCA never actually made them!) after the US Army Artillery Corps requested a tube that could stand up to the immense trauma that came with repeated firing. Apparently, large field pieces would chew through tubes in no time.

5692s are characterised by their extremely-short bottle form factor, vastly oversized plates and extremely liberal use of support posts. Almost all 5692s have small top getters and double micas on top.

Fact 1: The 5692 was patented in 1949, but was not produced en masse till around 1951. Hence this would imply that there is no such thing as a 1940s 5692.

Fact 2: The widely advertised of ‘10000 hrs life’ for the 5692 is just advertising baloney. If one would observe carefully, the 5692’s specs differ quite greatly from the 6SN7s – far lower plate voltage and max dissipation rates are given. It can be inferred that this conservatism in its ratings contributes directly to the 5692’s purported long life. Hence, if you intend to use the 5692 as a drop-in for a 6SN7 in an amp running 6SN7 voltages and currents, be prepared to have your 5692 last no longer than a normal 6SN7 at best.

Fact 3: By the late 1960s, tube manufacturers were relabelling tubes willy-nilly in an attempt to minimise their losses in what was essentially a dying market. There are many instances of 6SN7GTBs/WGTs/ being labelled as 5692s and passed on to the market. The vice-versa applied too; 5692s were relabelled as other 6SN7 types. Hence when verifying potential 5692 purchases look out for the 5 extraneous free-standing (ie. not attached to a grid/plate) support posts.

Fact 4: Only 3 American companies are definitely known to have made 5692s – General Electric (“RCA” 5692s were made by GE) [red bases – colour varies from a cherry-red to a deep red easily confused with brown], CBS/Hytron [brown bases] and Sylvania [black bases]. Raytheon purportedly made a small batch of brown-based 5692 [the CK5692 – apparently the mica shape was slightly different from normal CBS/Hytrons], but as CBS/Hytrons were known to be relabelled as Raytheons, this remains a mystery. If you know the answer to this, let me know...

Fact 5: There is only one known non-American make of this tube: Swedish Standard Electric 33S30, which can be distinguished by the micas and the plates always having a serial number scratched on.


5692, CBS-Hytron [PHOTO HERE]
[black plates, top getter, brown base] [known to be relabelled as Raytheon 5692 and Raytheon 6SN7WGT]
● “Fast, good dynamics, lot of air and great timbre” –Chimera
● “WOW!! this is one of the incredible tube swaps I have ever done. This tube improved everything greatly. amazing improvements in detail, imaging, soundstage depth and bass tautness.” –Tuberoller
● “The RCA or CBS 5692 is a good tube, but doesn't get to the top of the list. It has much weaker bass, is very nice tonally, and the highs are a bit recessed.” –Robert H

5692, RCA Red Base (made by GE) [PHOTO HERE]
[grey plates, top getter, red base, 1950s vintage - white labels, 1960s vintage - orange labels] [known to be relabelled as GE 5692]
● “Very warm sweet sound, great on voices and jazz” –Chimera
● "RCA 5692 red base. I finally found out why people like this tube. It hasn't sounded good in any other 6SN7 amp I've used. In the Wheatfield, it's got plenty of detail and a nice "lush" tubey sound." -Hirsch [in Tuberolling the Wheatfield HA2 thread]
● "Warm. Lush. Romantic - these words spring to mind immediately. Better air than even the TS RP. Seperation and detail are on par with the best of them imo. Slightly tubby bass. Good impact. Amazing with jazz and pianos. Never harsh sounding." -adhoc
● ”The RCA or CBS 5692 is a good tube, but doesn't get to the top of the list. It has much weaker bass, is very nice tonally, and the highs are a bit recessed.” –Robert H

5692, Sylvania [PHOTO HERE]
[black base, top getter, yellow 'Sylvania' label on glass] [RUMOURED TO BE RELABELLED Syl 6SN7GTBs. BEWARE!

]
● “5692, Sylvania, very fast , good bass and dynamics, lot of air and great timbre. My favorite tube in my current system.” -scottpaul_iu
● “All the black base Syl 5692's I've seen are rebranded GTB'S - THEY DON'T EVEN LOOK LIKE 5692'S! But there are real Sylvania 5692's that have the 5692 construction and brown bases, these are the ones I suspect the comment refers to. It's interesting that such an ordinary sounding tube caught on in such a big way with some audiophiles despite it's poor sonics. It first came to attention in the 1980's when the 6SL7 version, the 5691, was used in an MFA preamp. The 5691's good performance in that unit and it's cool red base caught the interest of some 6SN7 users, particularly in the Orient - where most of the MFA production was sold, hence where the buzz first caught on. The 5692 then started to get a bit of circulation, at which point Peter Qvortrup of Audio Note UK had amassed a sizeable stash of them and, finding he could get outrageously high prices for them from his bespoke customers due to their rarity and the unique red bases, proclaimed them "the best" - conveniently to support the prices he was charging. It all caught on from there and, like so much of audio, has no bearing to reality.” –Robert H. (in personal correspondence)




- 5. VTV’s TUBE RANKINGS

This section is included for informational purposes and for the sake of completeness - I also find it interesting to compare my taste in tubes with others.

Please do NOT use this section as your SOLE reference. This is why:

Vacuum Tube Valley (VTV) have in the past been accused of a conflict of interest as they also sell tubes. Suspiciously, after this review came out, VTV suddenly had stock of all the top-rated tubes. Some of the top-rated tubes were previously unknown and unloved AND stocked only by VTV.

1. Mullard CV-181: 97 / Sylvania 6SN7W ('40's vintage): 97
3. Raytheon 6SN7WGT: 96
4. Sylvania 1950s top getter Sylvania 6SN7GT: 95
6. GE 6SN7GTA: 94
7. Brimar CV1988 (brown base, 1950s): 93
8. Brimar CV1988 (brown base, 1972) / CBS 5692 / RCA 5692 (red base, 1950s) / Tung-Sol VT-231 (round black plates, smoked bottle 1945): 92

“I questioned the independence of the VTV crowd quite loudly on Tubes Asylum and got a whole lot of deletions and grief for it - they are a sponsor, after all. But not only did VTV coincidentally suddenly have stock of their top rated ones for huge prices when the issue came out, all of a sudden Kevin Deal turned up a big stash of the Raytheon WGT's that were second on the list.

But despite those misgivings, I must admit I have found their rankings to have stood the test of time, while there can always be debate and quibbling about subjective rankings, overall, it's pretty close to the mark.

I just wish VTV didn't have this awful smell about it.” – Robert H. (in personal correspondence)





Version History:
1.0 - 140505 - Original thread started
1.0.1 - 140505 - Minor correction made: 'CHY' replaced 'JHY' for VT-231 designation. On Hirsch's advice, point on CBS/Hytron vs Hytron added. On RobN's advice added some more similar tubes after further research.
1.0.2 - 150505 – Have completely overhauled the 6SN7 substitute section
1.1.0 - 150505 - MAJOR ADDITION: indicated which tubes I have PHOTOS for.

1.1.1 - 170505 - Corrected some minor spelling errors.
1.1.2 - 200505 - Added some more opinions. Added photos for the CBS/Hytron 6SN7GT.
---
1.2.0 – 220505 – MAJOR ADDITION: Opinions from another thread added.
1.2.1 - 270505 - Some additional opinions added.
1.2.2 - 290505 - Minor details regarding the 5692 RCA Red Base’s label colors added.
---
1.3.0 - 020605 - Major overhaul of tube descriptions done. Photos added for Syl non-1952 6SN7GT, Syl 5692, RCA 6SN7GTA Side Getter, GE 6SN7GTA.
1.3.1 - 040605 - Added some opinions on the TS RP.
1.3.2 - 080605 - Corrections made to spelling/grammar.
1.3.3 - 130605 - More spelling/grammar corrections and tube descriptions have been finally completed
1.3.4 - 180605 - Opinions on Syl Yellow Label GTB & RCA 5692 added.
---
1.4.0 – 250605 - TONS of opinions from selected Audio Asylum members [Robert H added for now, Jack G and Chris Garrett coming soon]. Tube descriptions for MANY tubes beefed up for greater clarity. Special 5692 ‘facts’ section added. Section 5 on VTV’s rankings added. Added under section ‘substitutes’ tube types 6SN7GTC and GTY. Added section on the Mullard CV181. Added some more tubes to the fray – CBS/Hytron 6SN7GTB, Raytheon 6SN7WGT, Telefunken 6SN7GT/GTA.
1.4.1 – 260605 – Added the Amperex 6SN7GT. Beefed up the small section on 7N7 – there’s a minor history lesson there now.

1.4.2 – 030705 – Added more details on the Telefunken 6SN7GTA. Found pictures for it too.

1.4.3 - 170705 - ADDED a LOT more details to the descriptions for a LOT more tubes. Now it's might even be possible to identify tubes without photos!

1.4.4 - 141205 - Added the Tung Sol 6SN7GT White Label to the list. (Thanks nmculbreth!)
2.0.0 – 060606 – MAJOR changes made. Lots of new stuff by Robert H. added. Enjoy people. This project is far from over.

 

[adhoc]

some background on this thread:

i've only recently been converted to the 'light side' of tubed amplification (

). for someone who has been a solid-state advocate his entire life, the avalanche of knowledge that came with my conversion was, to say the least, extremely daunting.

top getters vs side getters, GTA vs GTB, t-plate vs round-plate, black plates vs grey plates - all these were extremely confusing to a newbie like me. add to this the fact that most of the information regarding well-regarding tubes were scattered far and wide over n threads with n^n pages and well.. you get the idea.

enter The 6SN7 Reference Thread - here I have condensed all of what i consider the information needed to make an informed decision on which 6SN7 tube (or a similar variant) to choose.

I have tried as much as possible to avoid quoting impressions which result from a mixture of 6SN7s, but i have made exceptions for posts which clearly opine over a particular tube's qualities.

tubed people of head-fi, this is my gift to you. enjoy!

please do continue to post all further opinions on tubes you may have. i'll add them to the list. please do inform me too if i've gotten anything wrong.

 

[tom hankins]

With all the amps out there using this tube. This needs to be a Sticky.

 

[e_dawg]

Brilliant. Absolutely brilliant, adhoc.

 

[Rob N]

Great idea

A few things you might want to add:-

You can also use a B65 made by Marconi/Osram/GEC which has either a metal or plastic base.

The Telefunken 6SN7GTA commands high prices but IMO doesn't sound as good as the older 6SN7W/GT/VT231 types

As with the ECC32 in some applications you may be able to use the ECC34 which has lower mu than a 6SN7,and also the ECC33

 

[adhoc]

ver1.0.2 - did a major overhaul of the 6SN7 substitutes section.

 

[purk]

Many thanks man. I really appreciate the info. Being a new owner of Single Power amp, this thread is very helpful.

 

[adhoc]

MAJOR ADDITION - indicated which tubes i have close-up colour photos of. this should help people confirm tube types and might even prevent attempts at fraud - conmen rarely get all the prints correct when attempting to counterfeit tubes.

it would be nice if someone could host the photos for me though. free photo-hosting services would definitely NOT be able to handle the throughput for what i have in mind.

EDIT: wait.. wasnt head-fi supposed to implement a photo-hosting service?

EDIT: to the mod who gave me a custom title - a BIG thank you! i feel, well, really special now.

 

[Dhw]

While I probably won't own a tube amp anytime soon (besides my Traynor guitar tube amp...mmm...), I still think this is an impressive compilation! Great job! (informative postings like this keep me hooked on this site!)

 

[rickcr42]

Quote:

EDIT: to the mod who gave me a custom title - a BIG thank you! i feel, well, really special now.

that would be the boss man,Jude.

only a 'supermod" can do custom titles and he is the only one with that title.

Quote:

EDIT: wait.. wasnt head-fi supposed to implement a photo-hosting service?

There IS a picture hosting site and found on the main forum page

 

[ayt999]

so what about the 6SN7A, 13D2, CV1986, CV1988, CV3627, and 6N8S ? there might be more, but that's what I have offhand.

also, maybe the 5692 under the tube types should be in bold like the others.

 

[adhoc]

Quote:

Originally Posted by ayt999 so what about the 6SN7A, 13D2, CV1986, CV1988, CV3627, and 6N8S ? there might be more, but that's what I have offhand. also, maybe the 5692 under the tube types should be in bold like the others.

done. even threw in the 6H8C for good measure.

Thanks rickcr42 for the heads-up regarding photo galleries - i cant believe i've overlooked that link for so long!

 

[rickcr42]

Quote:

Thanks rickcr42 for the heads-up regarding photo galleries - i cant believe i've overlooked that link for so long

All good.I "lose" my glasses all the time

"anybody see my glasses ?"

Once the giggling starts I realise I am wearing them

 

[SHVentus]

Adhoc,

Great post. Just wish you had posted earlier. Great contribution. Thanks.

 

[KenW]

Wow, what a post! Singlepower owners must be happy to see this!

Of course, those of us who own the Raptor won't benefit but surely someone will step up to the plate and do something similar for us?? C'mon...don't be shy.