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What 12ax7 tube brand is this?

davstev

davstev

Well-Known Member
Hi all,

I am no expert in tube identification, especially when the markings are partially rubbed off.

See attached pics. These are clearly 12ax7's made in the USA, but can anyone else tell me, based on the white circular logo, what it might be? Any idea when it was made?

There is no marking on the underside.

Thanks!
 

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davstev said:
Hi all,

I am no expert in tube identification, especially when the markings are partially rubbed off.

See attached pics. These are clearly 12ax7's made in the USA, but can anyone else tell me, based on the white circular logo, what it might be? Any idea when it was made?

There is no marking on the underside.

Thanks!
Click to expand...
The etched dots suggest GE
 
Excellent to know! I'll look into this tube online. But, what would the general consensus amongst tube lovers/audiophiles be regarding this tube? Say, compared to a strong testing mid-60's amperex 12ax7?
 
In my system the GE is ok sounding. It has a wide bandwidth but is kind of veiled. Your questions is very system dependent. Tube rolling will show you the way. What is this tube going into?
 
The GE's are in a rather sonically important position in a really nice Fisher 500C. I have a hunch that the GE could be improved upon with a vintage Tele, Amprerex or RCA, however, it sounds nice enough. Nothing to balk at.
 
The Fishers came stock a lot of the time with Telefunken, or Siemens. They may sound best with European tubes. The tubes closest to the front end will make the most difference. Drivers and Phase splitter positions are not as critical.
 
The V14 and V15 positions in which these GE's are right now, are in the sonically important line stage/aux preamp section. I would imagine that the Telefunken's, Siemens, or Mullards branded as Fisher are nicer than the GE's, and I am thinking of getting some 60's Amperex to put in V14/15. There are a couple of Fisher branded 12ax7's in the 500C but not in the 'important' positions, and, they are not the super-desired telefunkens; I think they are Mullards.
 
GE branded for Voice of Music as mentioned.

What it sounds like depends wholly on the gear. They were by far the best phono tubes I could find for the stock circuit phono preamp in my Stromberg-Carlson. They didn't hum and everything else did. I've run them in various things, never thought they had any particular sound, which I would say is a good thing. I'm largely insensitive to tube rolling, so if I can hear a change its probably messing up the sound in some objectionable way.
 
I have good results with GE 12ax7's in my 800-c (43000 series) in the Tone and voltage amp positions and the P.I.'s My 800'c in the console(10000 series Executive) has all Tele smooth plates. I find them too bright for my tastes so I got some more GE's and swapped out the Tone and voltage amp tubes and toned it down some. Also black plate RCA's are a good sounding 12ax7 in FISHER gear as are Sylvania tubes which FISHER used as replacements for Tele's post 1965 when they were switching over to Solid State and getting away from Tubes. .
 
Thanks everyone for the input. Has anyone tried Amperex in the preamp stage in a Fisher? I have a line on some Amperex Hammond branded 12ax7 made in Heerlen, Holland in 1968; as well as Philips (Amperex Holland) 12AX7 / ECC83 from the mid 60's. All testing really strong.

I guess I'll just take a chance. That's what tube rolling is all about!

I might also look for some black plate RCA's as per your recommendation, Larry.

Thanks.
 
Honing in on a pair of really strong testing 5751's, GE, black plates, to substitute for the GE long plate 12ax7's that are presently in the line stage/AUX position now.
 
Stay with the 12ax7's. Even tho the 5751 is a 12ax7 variant, it's gain (or mu) is 70, vs. 100 for the 12ax7. You probably won't notice the difference by hearing, but you'll have to increase the volume a little to get the same SPL. Not recommended for line stages on the FISHER's. You can use 12ax7 variants that have a mu of 100 with no loss off gain.
 
Thanks for the tip. I am really wanting to tube roll the v14 and v15 positions because I have a few bucks to play with and I have a hunch that the GE 12ax7's can be improved upon. So I am gathering that the tonal quality of the GE 5751 won't be different enough from the GE 12ax7 to justify the purchase.

What my "dealer" does have on offer is:

"We have a pair of GE 5751 with long black plates, triple mica stabilization and a D getter. They test strongly. Probably RCA manufactured.

We also have some Philips from their Heerlen (Amperex) plant in 1959 September.

A 7025 pair that are from the same factory April 1961.

I can offer a pair of Telefunken smooth plates with the labeling worn off"

Hmmmm.....things to consider.....
 
I can tell you that 5751's don't work so well in some phono stages. I had a set in my Sherwood without realizing it, and just thought that the phono stage sounded like a wet blanket over the speakers. Once I actually spent some time and looked at what was in there, I was able to fix it with just a handy pair of 12ax7's. I haven't spent any time changing them to see if it sounds better, but the right tubes are worlds better than the low gain ones. Probably depends more on the circuit, if you need all the gain they can offer its not gonna act right with a reduction. I guess phono stages are one where you need full gain.

They're probably great inside a feedback loop where any loss in gain would be compensated for. Maybe as an inverter tube or something.
 
Davstev-I see that you are in Montreal.While I don't know who/where your dealer is,there is a particular individual in our area to be avoided. Send me a PM for further info..
 
arts said:
Davstev-I see that you are in Montreal.While I don't know who/where your dealer is,there is a particular individual in our area to be avoided. Send me a PM for further info..
Click to expand...

Does that dealer start with RAD-- HOV---?

Yep, I know....besides being unscrupulous, he is also really unpleasant to deal with, so easy to avoid.

My dealer is in Toronto, Ring Music. Top notch.

Thanks for the tip!
 
gadget73 said:
I can tell you that 5751's don't work so well in some phono stages. I had a set in my Sherwood without realizing it, and just thought that the phono stage sounded like a wet blanket over the speakers. Once I actually spent some time and looked at what was in there, I was able to fix it with just a handy pair of 12ax7's. I haven't spent any time changing them to see if it sounds better, but the right tubes are worlds better than the low gain ones. Probably depends more on the circuit, if you need all the gain they can offer its not gonna act right with a reduction. I guess phono stages are one where you need full gain.

They're probably great inside a feedback loop where any loss in gain would be compensated for. Maybe as an inverter tube or something.
Click to expand...

I was thinking of the 5751's for the AUX/Line in stage, so I guess, that is a preamp but not a phono preamp/stage. But good to know anyhow. Yes, it would seem to me that the faint signal coming from the cartridge would suffer a bit from a lower gain tube like a 5751.
 
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