GEC ECC81/12AT7? (tube pics)

NOS, modern, dating and identifying.

GEC ECC81/12AT7? (tube pics)

Postby dai h. » Fri Jun 20, 2008 6:10 am

stumbled on (apparently a Vietnam-located vendor) selling "GEC ECC81/12AT7" (which appear different from Mullard). Don't know much about them but in case this is of interest:

http://www.natubes.com/data/images/prod ... ge_220.gif

http://www.natubes.com/data/images/product/large_93.gif

http://www.natubes.com/data/images/prod ... ge_132.gif

http://www.natubes.com/index.php?page=p ... arentid=61
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Postby 908ssp » Sat Jun 21, 2008 10:43 am

Those look really cool. Too bad they aren't 12ax7 tubes. Still if the price was right I would try some. 8)
Alex

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Postby David B » Sat Jun 21, 2008 2:20 pm

Hey Dai,

wonder how they'll hold up to the abuse in a Fender reverb driver ?


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Postby dai h. » Sat Jun 21, 2008 3:43 pm

hey David (and Alex? was it?), sorry I know nothing about these tubes other than vaguely recalling reading something about the existence of a GEC ECC81 (Tube Asylum??). I thought perhaps this "Teonex" ECC81 (see my flickr page below) I have might have been a GEC since it has a solid getter (which the GEC supposedly had) however when I googled for "GEC ECC81" I came up with those pics above on that vendor site (which don't appear the same as the Teonex), so I'm back to a bit of puzzlement again. On the tube itself I couldn't see a code and the overall appearance looks more W.Euro to me than American, Japanese, E.Euro, etc. I also have a couple of Teonex branded EZ40 (small rect. like an EZ80 in the weird Rimlock basing) which I'm pretty sure must be from one of the Philips family companies (has "made in England" on the box and "Holland" on the tube itself IIRC). Oh and also, the reason I was a little curious was because someone on PP stated GEC never made ECC 81/2/3 themselves, so I was wondering about that.

http://www.flickr.com/photos/7878340@N05/

ooh, Holland vs. Russia about to come on...
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Postby Jeff West » Sat Jun 21, 2008 5:23 pm

Hey guys- A statement that GEC never actually manufactured ECC81, 82, or 83 equivalents themselves would definitely be too generalized, not accurate.

The A2900/CV6091 like you showed Dai were made by GEC, and I think they're entirely interchangeable with 12AT7. CV6091 is listed in Stewart's "History of the Marconi Osram Valve" as equivalent/CV designation of A2900 as made by M-OV.

In general, the factory code that appears with the "KB" when a tube was accepted in UK for British mil or postal svcs (like "Z" on some of these) is supposed always to reflect the factory where the tube was actually pumped and sealed, and I think they were pretty consistent about that because one big part of mil acceptance (in U.S. too) was being able to trace the origin of the tube. I know that in U.S. anyway, JAN standard compliance certification was issued to a specific [i]factory[/i], not the overall manufacturer, so for example RCA made JAN 6V6GTYs at Woodbridge, NJ plant with certification, but couldn't expand that production to Indianapolis in times of heavier demand even though the millions of classic blackplate black base RCA 6V6GTs were made at the latter.

Can't make out any acceptance or other dates on the particular ones shown, but GEC CV6091s I've seen like some of those have had mid-late '60s dates.

B309 was another 12AT7 sub with some made directly by GEC I believe, although they also may have selected some from other manufacturers. These usually look more typically like other 12AX7, w/shorter plates. FWIW, check this:

[url]http://img100.imageshack.us/img100/1268/img9236al9.jpg[/url]

[url]http://img100.imageshack.us/img100/898/img9241zt9.jpg[/url]

[url]http://www.head-fi.org/forums/f44/fs-two-old-rare-great-sounding-12at7-tubes-earmax-earmax-pro-se-ae-203313/[/url]

Might seem puzzling from our audio/guitar perspective that GEC would make AT7 version themselves in the late '60s and not AX7, but I think this reflected gov't demand rather than retail.

Thanks for making available photos of some of your tubes, Dai, I'll take a look.

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Postby dai h. » Sun Jun 22, 2008 7:27 am

thanks for the interesting info Jeff. I'll try to dig out some of the seemingly more unique tubes I've got and get some more tube pics up there.
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Postby Jeff West » Sun Jun 22, 2008 6:33 pm

Here's one (A2900) with 12/64 GEC date:

Image

Can't really tell from this photo, but these have a solid circular flash shield at top with getter above that, not usual halo as it might appear.
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Postby David B » Mon Jun 23, 2008 6:34 am

Hi Jeff,

Are the specs for the A2900/CV6091 listed in History of the Marconi Osram Valve and if not have you seen them elsewhere?

Nice pictures guys 8)


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Postby Jeff West » Mon Jun 23, 2008 8:53 am

http://tdsl.duncanamps.com/pdf/a2900.pdf

I don't remember it mentioned in Vyse & Jessop, but lots of valves GEC made aren't, it discusses examples of different significant types but not comprehensive lists after 1940. It is listed in Fin Stewart's "History of GEC and the Marconi Osram Valve", but not with specs. There's other info on CV6091.

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Postby dai h. » Mon Jun 23, 2008 9:29 am

cool picture. Wonder what they would have been used in. The rod would seem to make for a stiffer internal structure and intention of low microphony.
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Postby David B » Mon Jun 23, 2008 6:18 pm

Duncan's! now why didn't I think of that? :lol:

dai h. wrote:cool picture. Wonder what they would have been used in. The rod would seem to make for a stiffer internal structure and intention of low microphony.


now I'm curious how well that valve will perform
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Postby Jeff West » Wed Jul 02, 2008 8:55 pm

Regarding interpretation of stuff about GEC 9-pin miniatures on the internet, I think some tube fans have been inclined to make the following assumptions that are reasonable but not necessarily accurate: since the high-profile B739/49/59 invariably were selected from other manufacturers valves, that means GEC themselves never made any versions of ECC81/82/83; any GEC manufacture of ECC81/82/83 equivalents would include versions of all three types.
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