Help me identify some 12ax7 tubes, please?

[thehoj]

I recently got a few old 12ax7/7025s which I would like to determine the origins of.

I've got 4 that are labelled, and I'm trying to figure out who the actual manufacturer is, here are links to pics of them:

RCA (you can faintly see in one pic "HOLLAND": http://vwtweaked.ca/images/12ax7s/rca/

Two identical sylvanias (one of which I believe says made in Hungary in pic IMG_5591.JPG its hard to see in the pic but I can make out an H an N and a Y):
http://vwtweaked.ca/images/12ax7s/sylvanias/

Westinghouse: http://vwtweaked.ca/images/12ax7s/westinghouse/

And then I have this one which I can't make out any label other than 12ax7:
http://vwtweaked.ca/images/12ax7s/unknown/

Any help in identifying this would be greatly appreciated.

[DT7]

I'm pretty certain #2 is Tungsram...made in Hungary.

[Timbre Wolf]

Your "RCA" is a Philips-made 12AX7A, and is probably from their Heerlen, Holland plant. Look for a slanted delta (triangle) symbol, toward the bottom side of the glass, for confirmation.

The Hungarian "Sylvanias" are Tunsgram, as DT7 said.

The "Westinghouse" is an RCA 12AX7A

The last one is also an RCA - long gray plate.

Enjoy those tubes!

- Thom

[rockon1]

Originally Posted by Timbre Wolf

Your "RCA" is a Philips-made 12AX7A, and is probably from their Heerlen, Holland plant. Look for a slanted delta (triangle) symbol, toward the bottom side of the glass, for confirmation.

The Hungarian "Sylvanias" are Tunsgram, as DT7 said.

The "Westinghouse" is an RCA 12AX7A

The last one is also an RCA - long gray plate.

Enjoy those tubes!

- Thom

Bob

[Timbre Wolf]

Originally Posted by rockon1

Bob

Beat you to the punch, this time. Next one's yours

- T

[thehoj]

I've posted these pics around at a variety of locations, and this seems to be the general consensus. A few have noticed the delta mark, and have mentioned that it is an amperex 7025 made in 1957.

I'm using the tubes in an orange ad30htc, and my impressions so far are not what I expected. I thought that the "westinghouse" rca would be my favorite on my dirty channel in the first preamp tube position.

It turns out that on that dirty channel my favorite combo is both of the tungsrams, one in the preamp spot and one as the PI.

On the cleaner channel I like the long-plate RCA in the preamp spot, and the philips / amperex in the PI spot.

Although I haven't had a chance to put this through it's paces completely.
I found that the "westinghouse" rca or philips / amperex in the dirty channel made it too muddy.

I'd like to play around with some other nos preamp tubes just for the fun of it, see if I can capture "that" sound. Any suggestions for a tube that would be more articulate with chords, maybe something that's a bit brighter than the tubes I've been playing with?

Thanks for the input everyone.

Originally Posted by Timbre Wolf

Your "RCA" is a Philips-made 12AX7A, and is probably from their Heerlen, Holland plant. Look for a slanted delta (triangle) symbol, toward the bottom side of the glass, for confirmation.

The Hungarian "Sylvanias" are Tunsgram, as DT7 said.

The "Westinghouse" is an RCA 12AX7A

The last one is also an RCA - long gray plate.

Enjoy those tubes!

- Thom

[rockon1]

Originally Posted by thehoj

A few have noticed the delta mark, and have mentioned that it is an amperex 7025 made in 1957.

.

Cant see full code but its later than 57 since its a short plate not a long plate. The earliest short plates were made in the last half of 59. If you can see the full code and post it perhaps we cant get more detailed on its DOB . Bob

[Timbre Wolf]

Originally Posted by thehoj

I've posted these pics around at a variety of locations, and this seems to be the general consensus. A few have noticed the delta mark, and have mentioned that it is an amperex 7025 made in 1957.

As Bob alluded, that might be a 1967 Heerlen Philips (Amperex or Miniwatt), since it is a short-plate 12AX7A style, not long-plate like '57 production.

Originally Posted by thehoj

I'd like to play around with some other nos preamp tubes just for the fun of it, see if I can capture "that" sound. Any suggestions for a tube that would be more articulate with chords, maybe something that's a bit brighter than the tubes I've been playing with?

Well, the true '57 Amperex long-plate 12AX7 (mC type) would certainly give A MEMORABLE sound (that sound?).

I would highly recommend Ken-Rad 12AX7 (long black or silver plate) for bright, clear, balanced sound, with slightly early breakup. Raytheon long black-plate 12AX7A are bright and clear, with early-breakup (also more common than Ken-Rad), with more upper-mid emphasis. Sylvania long black-plate for later breakup, bright and clear. Long black-plate RCA for a thicker-sounding clear tube (with early-breakup). Don't overlook later tubes, like Ei silver-plate, for a budget clear and bright (not as suave as early-'50s Sylvania though).

- Thom

[thehoj]

Originally Posted by rockon1

Cant see full code but its later than 57 since its a short plate not a long plate. The earliest short plates were made in the last half of 59. If you can see the full code and post it perhaps we cant get more detailed on its DOB . Bob

I can't make out any more of the codes.
I'm not entirely clear on how to decipher them actually either. I can see that there's 1-57 listed, and then also XXMG. How are these translated?

Originally Posted by Timbre Wolf

As Bob alluded, that might be a 1967 Heerlen Philips (Amperex or Miniwatt), since it is a short-plate 12AX7A style, not long-plate like '57 production.

Well, the true '57 Amperex long-plate 12AX7 (mC type) would certainly give A MEMORABLE sound (that sound?).

I would highly recommend Ken-Rad 12AX7 (long black or silver plate) for bright, clear, balanced sound, with slightly early breakup. Raytheon long black-plate 12AX7A are bright and clear, with early-breakup (also more common than Ken-Rad), with more upper-mid emphasis. Sylvania long black-plate for later breakup, bright and clear. Long black-plate RCA for a thicker-sounding clear tube (with early-breakup). Don't overlook later tubes, like Ei silver-plate, for a budget clear and bright (not as suave as early-'50s Sylvania though).

- Thom

Thanks! I'm going to do some research on these.

[Blue Strat]

It's good to try everything everywhere, as you have, rather than rely on forum opinions of others. Good work!

I'm often surprised at what customers and forum members find to be "best for them" in particular sockets in particular amps.

That said, don't assume that negative experiences with, for instance, your RCA is typical of all tubes of the same type. We have no idea how strong your tubes test and even identical specimens that test fine can sound different.