12AX7 vs. 12AX7A/7025?

[cdw2000]

Hello all,

I was wondering about your opinions on the 12AX7-type preamp tubes. My current scratch built amp is using old, used 12AX7 tubes, but I recently noticed Fender specifies 7025/12AX7A tubes in their later amps.

The 7025 and 12AX7A data sheets both say: "For high-fidelity audio-amplifer applications critical as to noise and hum."

The 12AX7 data sheet simply says "For use in mobile communications equipment"

So, I'm wondering if you have heard a noticeable difference between these tubes. Especially reduced hum... are the 12AX7A/7025 tubes really better?

Thanks,
-- Chris

P.S. My scratch built amp is coming along great. There is some low level hum, but not objectionable. I'm just looking to optimize.

[cdw2000]

Wow, nobody has an opinion on this?

How about:

What brand of 7025/12AX7's do you prefer and why?

[CzarSketch]

i'll respond to the 2nd part, hopefully it'll keep it high enough on the forum for you to get an answer on the first part too.

I have an old RCA in my CVR that just sings. Absolutely beautiful overtones, and no matter what I do with my CVR--probably selling--I will keep this tube. They retail for around 70 a pop on fleabay, so I suggest finding them in old audio equipment. Hammarlund ham-band radios have at least one in them...

[rudutch]

I have has good results with JJ's both long and short plate. Not impressed with Sovtek (which is what Fender has been using for some time)

google seach "12ax7 types"
http://store.triodestore.com/12axec7057.html

[Kap'n]

Back when tubes were made in the Western hemisphere, the names 12AX7, 12AX7A and 7025 had meaning.

Now it's all marketing.

[fitlikemun]

Hi there, i installed one of these into position 1 in my hotrod deville, ECC83/5751/G.E-CRYO, followed up by, ECC83/STR/HARMA CRYO, in position 3 and 4.
I noticed, for the better, a HUGE difference in tone and general noise reduction. I got my valves from Watford valves in the UK, the guys are awesome there, will speak for ages going through different ideas for your valves.

http://www.watfordvalves.com/


ECC83/5751/G.E-CRYO - This is a superb sounding tube for audio as well as guitar application. It was used in audio by the high end audio manufacturer CONRAD JOHNSON in it most expensive designs and was used by STEVIE RAY VAUGHAN in his Fenders. The tube has a lower amplification of 70 mu as opposed to a 100 mu of a ECC83/12AX7. This makes it harder for the valve to distort and therefore an ideal choice when the best clean sound is required. The 5751 has the classic sound stage that G.E tubes are known for with plenty of top end detail and clarity. These are a great choice for taming down that hard Hi gain sound. They are also a superb audio tube providing sharper imaging and detail than standard ECC83/12AX7 types.This is a specially treated cryogenic version.

ECC83/STR/HARMA CRYO - The new Harma STR ECC83 is a recreation of the famous Telefunken ECC803S.The valve has a frame grid construction which eliminates microphonics. The grids are all gold plated as the original Telefunken The valve is the most neutral and has the warmest vintage tone of all the current production ECC83/12AX7 types. This makes it a great choice for clear Fender sounds or warming up a harsh amp. The tubes are all tested for low noise, low microphoney and are drive tested with a gain rating of between 229 and 249 digital points. This is a specially cryogenically treated version.

I hope this helps.

[Kap'n]

ECC83/STR/HARMA CRYO - The new Harma STR ECC83 is a recreation of the famous Telefunken ECC803S.The valve has a frame grid construction which eliminates microphonics. The grids are all gold plated as the original Telefunken The valve is the most neutral and has the warmest vintage tone of all the current production ECC83/12AX7 types. This makes it a great choice for clear Fender sounds or warming up a harsh amp. The tubes are all tested for low noise, low microphoney and are drive tested with a gain rating of between 229 and 249 digital points. This is a specially cryogenically treated version.

Translation: We buy a tube from JJ (or New Sensor, or SED), throw it in some liquid nitrogen for a couple of minutes, and charge you a shitload more for the privilege of buying from us.

[CzarSketch]

i once saw a history of tube technology that showed the different makes and models of tubes and what the numbers meant, you know, back when the numbers made sense. It was part of some promotion for some new prod tube, and it had a whole section on new tubes too, which i think was a mistake, for hte following reasons:

the tube history up until the invention and adoption of transistors is neat, ordered, and looks like an engineer built the hierarchy of tubes itself and not just the individual models and designs.

the current state of tubes looks like a retarded ape on amphetamines took a marker and drew lines between random old tube designs and decided to cross-list them. This same ape apparently also started putting random letters and attaching them to all the old functional tube names until only another retarded ape could understand them. Or, a marketing expert. They're actually very similar genetically.

ugh.

[cdw2000]

Thanks for the responses. You verified what I was thinking- there is no distinction really these days.

It would be nice to think that they took the 7025 design and re-labeled it 7025/12AX7 rather than the other way around, but that is probably wishful thinking.

I guess I will stick with my OOS (old, old stock) tubes or maybe try some JJ's.

[Kap'n]

If you're lucky, it was designed as a 12AX7, and not some Chinese/Russian/Eastern-European design tube that was 'close enough' to be called a 12AX7.

[fitlikemun]

Of course there is a difference, a 12ax7 is not the same as a 5751. And as for the cryo tubes, magnificent, try them out. Read up on them first and check out reviews.
Granted, it is all confusing when selecting what you want.

[Gravity Jim]

Tell you what. newbie.... why don't YOU read up first (namely, some back numbers of this forum) before you decide to assume that any long-standing TFF member is "confused" about amp components.

[cdw2000]

Of course there is a difference, a 12ax7 is not the same as a 5751.

Your right, it's closer to a 12AT7. (5751 has slightly higher AF). :-)

Fitlikemun, If you read what Kap'n is saying - yes, once there was a difference, but current production tubes are most likely a compromise solution between similar spec'd tube types.

[fitlikemun]

Hey, i have not meant to cause offense.

[elicross]

oboy.

[Kap'n]

Hey, i have not meant to cause offense....there are a few who, because they have 9billion posts seem to think they can say what they like.

Sounds a little passive/aggressive to me.

I have not posted anything that's insulting. Just a mere statement of facts. How you interpret it is your own issue.

[elicross]

I don't know which member has 9 billion posts, but he seriously needs to find a second hobby.

[rudutch]

I have taken advice from amp tech's, amp builders, and people who have spent time and effort trying / testing / comparing when buying tubes.
I don't know right now how many companys are actually (currently)building them, where they are and who they sell to. Maybe there is only 3 or 4 manufacturers??
I do know there is some very slick marketing and several "brand names" out there.
I just got some russian military (marked CCCP with the star) EL84's
That are Reflektor (sovtec?) from 1977. They work

I have used and was impressed with JJ pre amp and Svetlana (winged C) power amp. I guess the EH tubes were okay too.
Tried some TAD's they worked well, had some other chinese tubes that were good. Westinghouse GE, all the old stuff, all good

I have a pile of Sovtec's, I don't care for any of them. I think they start bad and get worse. If you like 'em, that's great. I have found stuff I think sounds better.

It's kidna like buying columbian coffe. Are you 100% certain it came from coloumbia? Can you document that? does it taste good?
I don't know for certain...

Everyone is entitled to their opinion here, unless you become nasty.

[Kap'n]

I don't know right now how many companys are actually (currently)building them, where they are and who they sell to. Maybe there is only 3 or 4 manufacturers??

Russia has two manufacturers, the Reflektor plant that makes all of the New Sensor/Sovtek tubes as well as all the Mike Matthews' owned trademarks (current manufacture Tung-Sols, Mullards, etc.) The other is the one that makes Winged-C/SED tubes.

JJ, which is the former Tesla plant. Czech Republic, I think.

There are also a couple of Chinese plants. Shuguang and Sino. Maybe a third.



Anything that's current manufacture is made in one of those plants. Some things, like a couple of the Groove Tubes offerings and the TAD stuff, are exclusively available through those outlets.

Just about everything else....most of the Groove Tubes, Ruby Tubes, Watford Valves, etc. are the exact same tubes with different printing and packaging.

[rudutch]

So, besides being funny, Triode Electronics is fairly honest in this?
If I have to spend $120 on a set of tubes, I do appreciate some honesty / integrity.

(This is from their web site)

Our What We Say Is What You Get policy means that we don't relabel tubes with phony brand names, or put fancy gold lettering and boxes on them, or tell you that little elves in the Black Forest made them in order to charge you 5 or 10 times what they're worth. We guarantee the goods you get are actually the brand and type advertised. Power tubes are tested and matched at typical operating voltages and dissipation, many also are burned in for 24 hours (where indicated) in some cases power tubes are burned in matched at the factory (eg: most JJ/Tesla product). All tubes are new production (eg: like Sovtek, Svetlana, Tesla, Ei) or NOS (new old stock) and unused unless indicated otherwise.
Tubes include a 4 month exchange warranty against defects

[Kap'n]

So, besides being funny, Triode Electronics is fairly honest in this?

Yep, they aren't hucksters like the folks who sell tubes to Guitar Center.

They do need to update their site, though. Tesla doesn't exist anymore under that name. Ei, I think is toast, too.

If it's not add it to the list of manufacturers.

[JAM]

I ordered a choke and some other amp related parts from Triode for my recent home build. I've also bought tubes, but it's been several years. UPS lost the recent package, Triode had great service in getting me a replacement.

[JAM]

There used to be several Russian tube companies. Some info here (old info)

[Plugger]

Translation: We buy a tube from JJ (or New Sensor, or SED), throw it in some liquid nitrogen for a couple of minutes, and charge you a shitload more for the privilege of buying from us.

Sure, but the fascinating thing is that by parting with the all that extra dough, the consumer can somehow hear a huge difference...

"Wallet-ears" is a general (although not yet fully understood) phenomenon.

Maybe they should just just charge more for the HotRods to make 'em sound better in the first place...

-Mark

[cdw2000]

Regarding cryo-treated tubes, as a Reliability Engineer by profession (a specialized EE), the thought of taking something made of glass and metal and throwing it into liquid nitrogen gives me the willies.

To be fair though, their website does say that they use a gradual temperature change process.

Tubes are highly dependent on materials and coatings for performance, and I am not a materials expert, so I will not poo poo the supposed benefits of this process.

I do have a concern for the overall reliability. Regardless of the rate of temperature change used, because of the difference in the coefficients of thermal expansion, I would be highly concerned about the development of micro-cracks in the glass envelope around the metal pins. Once the cracks are formed, additional temperature cycling from usage could propagate those cracks, eventually compromising the vacuum.

It would be interesting to see how long these "cryo tubes" last relative to the same brand of non cryo treated tubes.

[Kap'n]

I also believe that at least some of the components of a tube go above the annealing temperature of the metals used.

[Plugger]

I also believe that at least some of the components of a tube go above the annealing temperature of the metals used.

Well, yes, of course... if you want to preserve the tone enhancing characteristics of a cryo treated tube, it goes without saying that you must _never_ switch it on.

-Mark

[cdw2000]

I also believe that at least some of the components of a tube go above the annealing temperature of the metals used.

A very good point. Any alleged benefits of the cryo process would be quickly undone - so play fast!

On another note - Whether this process has any benefits whatsoever, short or long term - I do think that it is a stretch for them to claim that the cryo process improves the tube microphonics.

Callaham is another vender that supplies cryo'd components. I love their bridges and trem blocks, but cryo treated potentiometers, wire, switches and jacks? - a bit of a stretch.

[Kap'n]

Jacks, maybe. Maybe they hold their springiness longer? I don't know much about what cryo is supposed to do to metals.

OTOH, I've never had a problem with standard Switchcraft jacks lasting decades.

[ziess]

Funny how when musical gear was just made better (ie. in Western Europe and in the USA) there was no need for any of this crap.
I run RCA blackplates in my Tweed Bassman clone that were probably made about 25 years before I was born. Not once have a been tempted to put them in the freezer.

Tommy.

[cdw2000]

Yeah, after reading these responses, I think I'm just going to stick with my Raytheon 12AX7, Eico/Mullard 12AX7 and GE 6V6GT that a friend's dad gave me for free out of his parts bin.