RCA 12AX7 tubes any better?

Scott Denniston · From: Hahns Peak, Colorado, USA

I've noticed that the average 12AX7 price is in the $10 range while the RCA 12AX7 is close to $50. It's NOS (new old stock?). I'm kind of wondering if it would be worth the $50 to see if it would do anything for my pre-amp that uses a 12AX7. I think it's got a Chinese in there now and was thinking about an Electro-Harmonix or a Tesla/JJ (each about ten bucks). Anyone know what makes the RCA so pricey?

Dave Grafe · From: Hudson River Valley NY

American electron tube manufacturers of the last century had a much higher quality control program than the current offshore ones, in quality and consistency of materials, construction and physical tolerances.

If indeed these are authentic "New Old Stock" RCA tubes they should be significantly more consistent electrically from tube to tube and less prone to microphonics and damage from transport, which translates into solid, consistent sound and longer overall life. Whether this is worth the extra $40, I can't say, but there definitely IS a difference, there aren't going to be any more made and thus they are pricey (and likely to become more so in the future).

[This message was edited by Dave Grafe on 01 March 2005 at 11:06 PM.]

John Daugherty · From: Rolla, Missouri, USA

Dave (or anyone who has the answer), How long has it been since there was a tube manufacturer in the USA? I have heard rumors for many years that there were only a couple manufacturers and they are in other countries (USSR for one).
I, for one, would not invest $40 in a 12AX7. But..... I am not that dependent on equipment to get a good sound from a guitar.

Jay Ganz · From: Out Behind The Barn

The best sounding 12AX7's were actually made
years ago by Mullard (in Great Britain) and
Telefunken (in West Germany). Brimar's are
also great (England) as well as Bugle Boy from
Holland.

Blake Hawkins · From: Florida

I have some RCA NOS 12AX7 tubes. One of them is marked "made in Korea."

Blake

Mark Herrick · From: Bakersfield, CA

What you would probably notice most is how much quieter they are than some of the lower priced current manufacture 12AX7's. I put GE 12AX7WA and Phillips 12AX7WA tubes in a couple of amps and you could immediately tell the difference between them and the Chinese tube that was originally in there.

As far as tone, I can't hear that much difference between them (the GE and Phillips) and the new Groove Tube 12AX7M (the Mullard copy.) I think the tone difference is probably more noticeable in a six string guitar application where overdriven tube sounds are more desirable. I'm sure there is some difference in the clean tone sound that most steel players seek but just not as much.

There is a lot of good information here:
http://www.kcanostubes.com/index.html#index

And you can always call Mike Kropotkin and get his advice. He's always been very helpful to me. And it looks like he has some "almost new" RCA 12AX7's that are about half the price you mention. Worth checking out at that price.

------------------

Michael Brebes · From: Northridge CA

I did some tests, when I had to replace tubes in a Summit Audio mic preamp, and found that the Electro Harmonix were both the quietest and had the best frequency response of the newly manufactured tubes. www.thetubestore.com gives a similar evaluation of the tubes.

Scott Denniston · From: Hahns Peak, Colorado, USA

Thanks for the replys. Yes-to quiet it down and retain (or improve) the tone and gain is what I'm after. The tube that I've got seems to be distorting more already too. It looks like I can do pretty well though without going all the way to an RCA. I'll probably try that Electro Harmonix. I can't see a label on the tube that's in there so I suppose they're not real proud of it.

John Daugherty · From: Rolla, Missouri, USA

If I remember correctly, Fender used a 12AY7 for the first stage in some tube amps. I think it is a low noise version of the 12AX7.
You might consider trying one of these.

Scott Denniston · From: Hahns Peak, Colorado, USA

Thanks John, I see Electro Harmonix makes a 12AY7 so I might order one (they're not expensive) to compare it with the 12AX7. I guess the trick is to find a tube that has less noise without sacrificing any gain.

Blake Hawkins · From: Florida

The 12AY7 is a medium-mu triode and the 12AX7 is a high-mu triode.
The low noise version of the 12AX7 is the 7025.
You may get less noise from a 12AY7 because it has lower gain.

Rocco Labriola · From: Chicago, Illinois, USA

I just replaced the 4 preamp tubes in my Evan Hybrid 300. The chassy is labeled 7025 and I put 12AX7 because everyone said they were a 'Suitable replacement for 7025'. Now I have the most horrible buzz, even when the guitar isn't plugged in.

Is it safe to assume 12AX7 are the cause? Is there a fix or do I need to track down 7025?

------------------

Mark Metdker · From: North Central Texas, USA

I know an old guy that lives way out in the sticks outside of town. He is a retired TV and radio repairman. Last I heard he had dozens of old RCA tubes, of all shapes and sizes. The last time I was there I ask him what types of tubes he had, and he said all kinds. I then ask him..."Do you have any tubes with the numbers 12 and 6 on them" He replied that he had LOTS of 12 series and 6 series power tubes. hmmmmm.....Maybe I need to make a trip out there and offer to take all those old tubes off his hands!

------------------
Zum U-12 w/True Tone pickup thru a Nashville 112

Strats thru a tweed Bassman

Band Pics
http://community.webshots.com/album/176544894AuXSmi

Mark Herrick · From: Bakersfield, CA

quote:
Now I have the most horrible buzz, even when the guitar isn't plugged in.
Is it safe to assume 12AX7 are the cause?

If that is all you changed, probably. You could try cleaning the tube sockets with contact cleaner. Or maybe you just need some better 12AX7's. The 12AX7 is interchangeable with the 7025. More info on interchangeability and gain:
http://www.kcanostubes.com/preampgain.html

I don't know if you can even get real NOS 7025's anymore.

Michael Brebes · From: Northridge CA

To clear the confusion: 7025's were 12AX7 tubes that had been tested to meet the "7025" low noise specification.
12AY7 has less gain than a 12AX7, therefore it will give the impression of being quiet because it has less gain.
Regarding the 7025 swapped out for a 12AX7, either the tube socket is not making good contact or the "new" tube is bad.

Gene Jones · From: Oklahoma City, OK USA, (deceased)

*

[This message was edited by Gene Jones on 04 March 2005 at 03:11 PM.]

Michael Whitley · From: Oxford, Mississippi, USA

I select a tube based on it's function in the circuit. A good US-made RCA (or the premium european tubes mentioned) might be worth the extra bucks (it is for me) for the phase-splitter tube (in Fenders and most others, this is the little one next to the power tubes). This tube does the "push-pull" thing, and a cheap tube doesn't always push as much as it pulls, which distorts the output. However, the tube in this position is usually a 12AT7.

To keep the sound clean, which is what most steelers want, you may want to stick with the lower-gain tubes in the preamp input positions, like Sovtek's 12AX7-WA ( not their -WB, -WXT, or Telefunkens ). For even lower gain, 12AY7s are cool. (If you run out of volume knob, you'll need to go back to a 12AX7) You can try a 12AT7 in these positions, but it may be too dramatic, and the -Y7 is a better tube. In a big Fender, these preamp tubes are the right-most tube, facing the back of the amp (for the normal channel), and the one next to it (for vibrato).

Mike Fried · From: Nashville, TN, USA

The 5751 is an excellent military-grade alternative - it has slightly lower gain than the RCA 12AX7, but higher than the 12AY7, so it doesn't affect the output volume as much. They are available NOS for less $ than the NOS 12AX7s, as the demand for them is lower.

Ken Fox · From: Nashville GA USA

I used NOS RCA and Sylvania for 2 years in amp restorations. Too many microphonic tubes for me! I switched to JJ/Telsa tubes and have had great results in sound quality and performance. I like the sound equally as well as the RCA tubes I used before.

Bobby Lee · From: Cloverdale, California, USA

When I was at Mesa Boogie (1980-1985) we tried tubes from all of the manufacturers of the day. The best and most consistent 12AX7 tubes we found came from China. Problem was they could never meet their delivery schedules - very frustrating! Tube shortages were common at the Boogie factory back then. Seems like we were always waiting for the next batch of tubes.

------------------

Bobby Lee - email: quasar@b0b.com - gigs - CDs, Open Hearts
Sierra SD-12 (Ext E9), Williams D-12 Crossover, Sierra S-12 (F Diatonic)
Sierra Laptop 8 (E6add9), Fender Stringmaster (E13, C6, A6)

James Quackenbush · From: Pomona, New York, USA

A friend of mine turned me on to some Shuguang 9th generation 12ax7's.....He swore by them .....I put them in one of my pre's , and LOVED what they did to the tone....Very consistant , and very inexpensive....I bought 20 of them I liked them so much ....$5 a piece is not a bad price for tubes that sounded better than a lot of tubes I paid $20 each for ....Jim

Forum Index > Electronics		Next oldest topic :: Next newest topic