6SN7 ID help

[n_maher]

Like the title says, I need some help ID'ing some 6SN7's that I'd like to list for sale. Basically, I just want to make sure that both parties get a fair deal. I'd rather not find out later that I sold a $50 for $10 or vice versa. I've got 10 that I'd like to list (of the way too many that I've accumulated) since I'm now pretty much exclusively using 7N7s. If you need more information just as, but I figured we'd start with pictures and go from there. And huge thanks in advance.

Batch 1:

Batch 2:

All have been tested on my Jackson which can do everything short of conductance (but it does have a better than average LIFE test). They all test good to very good and come with a plain white box.

[tkam]

In your batch #1 photo, the 2nd tube from the left the sylvania with the green lettering. Looks like a 6sn7w short bottle to me, very nice tube one of my favorite 6sn7's actually.

[n_maher]

Thanks Todd.

[Voltron]

Nate-

I am not very good at tube ID, but here is some info I found helpful to classify them at least. My "Bad Boy" 6SN7s have green Sylvania labels, but I cannot tell if the greenies in the second shot could be Bad Boys. The short bottles would not be Bad Boys as far as I am aware. If you feel comfortable PM'ing Earl, he could probably give you the most accurate/complete answer of anybody.

Source: 6SN7 Info & Links

6SN7 General Info and Types

Three envelope sizes are common in the full octal base version: SHORT, glass is 1.5 inches high; MEDIUM, glass is 1 3/4 inches high; TALL or "TALL BOY", glass is 2 inches high.

VT-231:

These are basically the military lableling for the commercial versions of the 6SN7 types described below. There are many different prefixes as well, depending upon the manufacturer-- Raytheon is CRP, Sylvania CHS, RCA CRC, CBS-Hytron JHY, Tungsol CTL, KenRad CKR. See my section section on this by clicking here.

6SN7GT / G:

This is the original version of this tube. It may be found in all three sizes of glass envelope. The Sylvania Tall Boy types have two triangular shaped plates facing each other mounted high in the tube, with either a top or bottom getter. The early Sylvania types had a top getter and silver flashed the entire top of the tube, sometimes called "chrome tops". Many brands used this design, but the high mounted triangular plates means it most likely was made by Sylvania. The early RCA "GT" types were usually in either a medium or short envelope and have a grey RF shield sprayed on inside the glass. The GE and KenRad types were similar, but the inner glass coating is deep black. These tubes usually have flat black plates, like large 12AX7 blackplates. The military versions of these are the VT-231 and are in very high demand today.

6SN7GTA / GTB:

This is the later improved version, and the improvements were primarily geared toward the TV chassis designers who demanded more max. plate wattage and voltage, where vertical circuits can put up to 1500 volt pulses at 7 watts on the plates. For hi-fi audio use, these improvements are meaningless. These are fine tubes, nonetheless. Most are found in the short glass envelope, but some brands like Raytheon used the Tall Boy style. Sylvania made tubes have the triangular plates mounted lower, and set at angles to each other, although some of the very earliest examples of the GTA types still used the dull blackplates facing each other. RCA used the flat black plates "sideways" to each other, and GE used the grey plates parallel to each other. The Sylvania types in demand have a large top getter patch. The earliest Sylvania GTA types have a green label and heavy top getter flashing extending down the sides of the tube. The early GTB types are similar, but have a yellow or red label. The versions from the 1960s have the getter just covering the top of the tube. All of these have the same black triangular plates and are excellent tubes. The GE types have a side getter and large parallel grey plates, and the RCA used both bottom or side getter. Most other vintage USA brands you find will have been made by these three vendors, and will be one of the above variations, regardless of brand on the label. A few were made with brown micanol bases, the RCA types being very dark brown, the GE types being a lighter, marbled brown. Many audiophiles prefer either the Sylvania chrome tops, the RCA, or the GE side getter over any others, even over the military or redbase types. These are all a great bargain now, and are sure to be rare and expensive tomorrow.

6SN7W / WGT / WGTA:

This type indicates a military spec tube that was not made for consumer use. These usually have extra support posts on the plate structure, heavy mica spacers, and brown micanol bases. These also have the famous triangular shaped black plates. They have been ruggedized to withstand shock, the brown low loss micanol base resists mold, mildew, and fungus growth, and they can withstand heat even if used upside down. The early Sylvania 6SN7W types from the 1940s had a metal collar around the base, then later a black base. These look internally alot like the early Sylvania GTA types listed above. Sylvania made these for other brands as well, including RCA. Easy to spot as they have the triangular blackplates facing each other in a short bottle, with a very heavy chrome top flashing extending down the sides of the tube. These are RARE and worth seeking out! The WGT and WGTA types all had brown bases. Only the WGTA types made in the late 70s and 80s reverted back to black bases then coin or wafer bases. These are all wonderful tubes, are long lived, and sound fantastic. No wonder they are fast disappearing from the vintage market.

5692:

This is the premimum commercial / "industrial" grade of 6SN7. The most famous of these are the RCA "redbase" series, with their distinctive red marbled full octal bases. These are always in the short glass envelope style, and most have four support rods joining the four corners of the top and bottom mica spacers and supporting the plate structure. These have 10,000 hour life filaments and are very resistant to shock and vibration, making them low in microphonics. The RCA versions have the "stop sign" label on the top of the tube with the number 5692 inside, and on the older tubes this was often smeared off, being printed with a chalky white paint. ALL of the redbase versions of this tube were made by RCA, regardless of the brand on the label. TungSol, GE, and Raytheon can often be found branded on the label, but RCA made them all. Other brands like CBS/Hytron and Sylvania made brownbase versions of this tube, but I suspect all were actually made by RCA, as they are identical inside.

The above info courtesy of Brent Jessee Recording & Supply, Inc. located at http://www.audiotubes.com<< a>

Interpreting Date Codes

This info was reproduced from Triode Electronics' website located at Commonly Seen EIA Codes

These are codes often seen stamped on components found in US made vintage tube equipment. This list is circa 1955, and some codes have been reassigned or added since that time.

Code formats were not completely standardized, but a little deciphering will generally yield the info of interest. Note that many makers also stamped OEM (Original Eqipment Manufacturer) part numbers above or below the EIA code, in some cases parts makers or the customer elected not to include the EIA codes, so not all parts have them.

They generally follow the following format: (example)

322 5904

where 322 is the manufacturer code (in this case Tungsol), 59 is the year (1959), and 04 is the week.

One alternate scheme is:

274 940

274 is the EIA code (RCA) 9 is the last digit of the year (in this case 1949). Usually single digit date codes are from the 1940's, but have on occasion shown up in later decades, even up to the 1970's. If one has a general idea of the age of the piece in question, usually the decade can be divined from that.

Another alternate is in the format following:

188-5 69 32

188 is General Electric. 5 is the plant code (in this case, Owensboro, Kentucky). 69 32 is 1969, 32nd week.

And another is like this:

322 6104-1

322 is Tungsol, 6104 is 1961, 4th week, 1 is the shift code (1 would probably be the day shift)

After about 1960, many tube manufacturers went to encrypted alphabetical date codes., such as:

KE

188-5

The reason was purportedly to allow factories to track the dates of manufacture of defective tubes (especially important in the case of OEM customers that might send back entire batches of tubes), but avoid possible consumer complaints about "stale" tubes. This sounds perhaps a little silly since the shelf life of tubes is decades, at least (indefinite in practical terms), but some OEM's might have beenn a bit irritated by occasional consumer complaints such as "my 1961 model TV has 1959 model tubes in it!"

Tubes made for the US military, or certain OEMs (such as some test equipment manufacturers) that requested it, continued to carry numerical date codes.

In years past, EIA (Electronic Industries Association) also went by the name of RETMA, and the original acronym of RMA (Radio Manufacturer's Association).

EIA Code Lists for:

Tubes and CRT's EIA code

Amperex (USA) 111

Bendix 125

DuMont 158

Eimac (Eitel-McCullough, Inc) 162

Electronic Tube Corp 169

General Electric Co (USA) 188

Hytron (CBS-Hytron) 210

Machlett 231

RCA (Radio Corp of America) 274

Raytheon 280

Superior Tube Co 310

Sylvania (Hygrade Sylvania Corp) 312

Tung-Sol 322

United Electronics 323

Western Electric 336

Westinghouse 337

Zenith Radio Corp (CRT's) 343

Nortn American Philips Corp 423

Taylor (aka Cetron-Taylor) 713

Lewis & Kaufman 738

National Electronics (also Cetron) 749

Penta Laboratories 771

Vacuum Tube Products 781

Varian Associates 809

Litton Industries 879

Electrons, Inc 935

[n_maher]

Thanks Al, that's quite a bit to digest but I'll have a go.

[Voltron]

The basics are most useful. The more esoteric codes and all that is beyond me.

[hirsch]

There is some misinformation on that sheet. For example, although the 5692 is usually compatible with a 6SN7 circuit, it is NOT a 6SN7. It cannot dissipate as much power as even the earliest of the 6SN7's, and an amp that drives the 6SN7 hard will fry a 5692.

The pics appear down, but the first step would be to identify the markings on the tube. Generally 6SN7GTB's are the latest version of the tube, but have the least value (and, in many cases, the worst sound). 6SN7 GTA's are more desireable, but the premium tubes are usually the 6SN7W and 6SN7GT. Value is dependent on brand and "coolness" factor. For example, the Ken-Rad VT-231 (military designation for 6SN7GT) has both a clear and black glass version. They sound identical, but guess which one usually costs more...

If you've got a short-bottle 6SN7W in there, it's worth more than $50, if it tests well. Only a few of the 6SN7GTB's would be worth more than $10 (although I'll admit it's been awhile since I priced that tube).

[n_maher]

Yeah, pbase is down so no pics till they get their act in order. I'll post the full alpha-numeric codes for each tube tonight.