Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by pfrischmann, Mar 14, 2006.
Sorry, new to this.....is it a mullard?
I cant really tell, but from the looks of it, with the getter slanted its not a mullard Ive seen. I could be wrong. Might be an amperex, maybe. Hope that helps-
Is there an "m" on the bottom?
Also- any etching/print?
No etching or print. I'm having the hardest time getting a good picture. There is no flash on install, The getter is slanted and that silver coating they put on top is also slanted....it doesn't cover the top part of the tube evenly, like someone painted it at an angle... I'm told it came out of a Bogen PA.
(Its really difficult to tell from that photo - please try without a flash next time.)
It has the Mullard/Philips-style (late '60s - '70s, short-) plate structure, which was also used by RCA. But if it is a Mullard, it would have the etch codes near the bottom (I63 on one line, B_ _ underneath it). Etch codes (I6_) would also be on other contenders in the Philips conglomerate (including Amperex, Miniwatt, Valvo, Bel).
I don't think it is an RCA: both 12AX7A and 7025 have flat cuts on both sides of the otherwise-circular mica disks, and both RCA and GE have distinctively-etched markings on the side. The plate structure is different from '70s/'80s JAN- GE, Sylvania, and Philips ECG.
Though I have no personal experience with them, I have seen photos of Matsushita (= Panasonic) ECC83 that have the slanted getter halo. Matsushita production was set up by Mullard engineers, and they had the Philips-style plate structure. It would still have an etch code on the side, near the base, I believe - with either "n" or "N" (signifying Matsushita) on it. Look at a recent eBay item #5871669487 for a photo.
I think some early Valvo ECC83 (I60 type etch code) also have slanted getter halos, and they'd have a "D" etch code (for Hamburg, Germany) near the base.
p.s.: Igneous - what does an "m" on the bottom signify? I've not heard of that.
It looks like a Brimar to me.
The shape of the bottle (slightly squarer at the top than the Mullards, with a more distinct ring around the pinnacle which you can't see in the pic, and no seam) and the angled getter ring/flash are typical.
The only thing that doesn't look right are that the little cutouts halfway up the plates look triangular in the pic (should be semi-circular) but it could be a trick of the photo.
I have no idea how you learn all this stuff! If you are talking about the little holes half way up the plates, they are round. I'm thinking it's a brimar as well.
I'll look for a code and try to get some better pictures.
Thanks again for the input so far.
Use the macro mode on your camera. This is usually indicated with a picture of a tulip on the button. If the flash is too bright, put your finger over half of it and try again. I've found with my cheapie Canon when you go to macro mode is turns the flash right down and the chances of getting a good shot are pretty good.
Looks exactly like a Matsushita, '70s I believe, in every detail I can see including the tall silver grid rods, shape of the bulb and even the blunted tip, as well as plates and getter ring, etc. so I agree with T-Wolf except that it's common that no codes are apparent at all on these, whether they've rubbed off (does happen, despite what you'll read sometimes) or were never there is unclear. Check the little cutout circular holes on the sides of the central raised portion of the plate on each side (4 total on the entire tube). They extend on the inner side of the plates, right? That is, if you view the tube perpendicular to the plates (not like the photos), you see a fully circular cutout hole with silver grid rod inside, bisected by the thin edge of the plate in the middle, correct?
This Matsu ID hypothesis assumes there are two crossed seams on top (four raised seams radiating out at right angles across the top from the middle tip, two a little fainter than the other two). Someone said the top is smooth but I'm betting not.
If you wanna get really obsessive, should likely have one tiny hole in the bottom mica spacer on one side of the plates, and a parallel hole but with an additional offset hole in this spacer on the other side.
The getter (silver coating on top) seems particularly prone to turn black on these with use, starting at the edges, even when it doesn't shrink too much, but of course other brands can do that too.
May be no molding characters, digits, etc. at all on the bottoms of these (by the pins), unlike many other 12AX7s.
These aren't bad tubes, IMO, and actually seem to really last with maintained performance over many years. Made in Japan but with Philips input. I think Marshall used 'em stock sometimes in the '70s.
Yes, if it has seams on top (I think I can just see one in the top new pic) it's not a Brimar. The grid rods do look a little too tall as well now I can see them. Everything else is nearly identical between the two.
It isn't hard to learn this stuff BTW... I'm holding a Brimar 12AX7 as I'm typing this . You just have to look closely.
I saw two seams running down from the top about 1/2 way. That's about it. Darn, I thought I found a Mullard..
Oh well, Any thoughts on how this would sound in my Marshall, compared to a nice Mullard.
probably good. Lots of people say the short plate mullards are nothing special anyhow but I sure like the ones in V1 and V2 of my deluxe.
I had this old tube laying around that said "silvertone" on it and i knew it sounded good, didn't think anything of it... pulled it out the other day to put in my brown super and noticed it said "made in holland." Interesting that such nice tubes were in the cheap silvertone stuff...