How do RCA tubes sound?

[Radioboy950]

Has anybody tried the old RCA 12AX7A pre amp tubes...or the rare 7025, considered by some to be among the finest 12AX7 ever made in the U-S? Some players just don’t buy into the whole NOS tube hype.

When it comes to new tubes, I do hear significant differences . JJ, Sovtek, Tung Sol, EH, Chinese…all have their own characteristics. One may be dark and fizzy, another ice pick thin. Some sound just right from low-mid-high. Together, they may sound magical. It depends on many factors, of course. But we're talking about $10 tubes here, so it’s a little more economical to experiment.

These rare NOS RCAs are fetching more than $100 each! Even the new-in-box 12AX7As are super-pricey. Too rich for me right now, but if any fretters use them, do they REALLY sound that great? Can you tell the difference between one of these and , say….a $15 Tung Sol reissue?

Whether they are worth the premium price...well, that's another topic.

 

[tot_Ou_tard]

Has anybody tried an RCA 7025, considered by some to be among the finest 12AX7 ever made in the U-S? Some players just don’t buy into the whole NOS tube hype.

When it comes to new tubes, I do hear significant differences . JJ, Sovtek, Tung Sol, EH, Chinese…all have their own characteristics. One may be dark and fizzy, another ice pick thin. Some sound just right from low-mid-high. Together, they may sound magical. It depends on many factors, of course. But we're talking about $10 tubes here, so it’s a little more economical to experiment.

These NOS RCAs are fetching more than $100 each! Too rich for me right now, but if any fretters use them, do they REALLY sound that great? Can you tell the difference between one of these and , say….a $15 Tung Sol reissue?

Whether they are worth the premium price...well, that's another topic.

$100? Yikes!

I'm sure that there is something sweet for a much better price.

I got my NOS RCA 5751 blackplate for way less than that.

 

[Bloozcat]

I still have one RCA 12AX7A in my box of NOS tubes.

Although it sounds great in most applications I've tried it in, to tell the truth, it's not much different than a Tung Sol 12AX7 reissue. Maybe a touch less warm than the Tung Sol, but if you heard the two in a blind test, you'd probably be hard pressed to hear a difference.

The one difference that could seperate the RCA from the reissue Tung Sol might be in how long the NOS tube will last. Since the Tung Sol reissues have only been around for a relatively short period of time, I think it's fair to say the jury's still out on the longevity issue. Even if they don't last as long as the RCA's, you can still get six plus of the reissues for the price of one RCA.

As much as I like NOS tubes, I'll go with the TS reissue before paying what they want for NOS anymore - unless I luck into a deal somewhere, but those are becoming as scarce as hens teeth lately.

 

[tunghaichuan]

The 7025 was specifically designed for audio. It was spec'd out as being low noise and low microphonics, IIRC. I've only seen one real 7025 in all my years of dealing with amps. It was in a mint-condition '65 Deluxe Reverb a friend of mine bought in a pawn shop. This amp looked brand new and still had all its original tubes. The 7025 came stock in some of the Blackfact Fender amps.

These days, the designation "7025" is just a buzz word. A modern tube marked "7025" is probably just a run of the mill 12AX7 or at best a 12AX7 that has been tested for noise and microphonics.

Bloozcat is right, NOS can sound a tad warmer but there are a lot of duds out there. Radio/TV repairment would routinely replace marginal tubes with new ones and stick the old one back in the box. With so many scammers out there it pays to be careful. If you buy NOS stick to well-know dealers with good reputations.

One of the reasons that NOS tubes are high-priced is that they do last a good long time. That, and they are not being made anymore.

Personally, I don't like the 12AX7 as a tube. I mainly use Sovteks I bought about 10 years ago as "hole fillers." I have lots of Mullards, a Telefunken, a pair of Aperex ECC83s, a few G.E.'s and some RCAs, but they all sound pretty much the same to me. But then again, I don't have golden ears. I don't really have much experience with new-production tubes although I thought the EH 12AX7 sounded pretty good.

tung

 

[Radioboy950]

Good info, gents.
As always, thanks:AOK:

Tung: on the EH... I have one in V1 right now, and it does sound good. Nice gain but a tad "thin" in my amp. But I warm it up with a JJ and a Tung Sol, and that seems to be a good combo.

 

[JJ Gross]

Personally, I feel older USA built tubes and some European tubes from pre-1970 are pretty much all better than anything new made anywhere. I belong to a club (my wife calls it the Geek Club) of guys who build amps, effects and guitars. I did a blind swap test with 3 different amps using new Groove Tubes, old GE and RCA and some ElCheapo Chinese tubes in all the amps. Even with their backs turned away, everyone in the room could tell when the good tubes were in the amps (96 Fender HRDx, 78 Fender Twin Reverb, 71 Ampeg VT40). It was like that with both power and preamp tubes.

The RCAs are going up in price, but if you buy used ones that don't have perfect printing on them (collector grade), you can get them for a lot less than $100 each. I personally use all old GE tubes in my gigging amp (HRDx) and only keep new tubes around as spares.

Another thing you'll notice in older tubes is most are able to handle abuse much longer than new tubes do. Most small combo amps put tubes at Ground Zero right behind the speaker in cabinets designed for increased bass response. That's a friggin tube torture chamber. Most new tubes I've put in the HRDx have failed in less than a year, but 30 year old tubes are still going strong (and tested on a tube tester) at 4 years running. Nobody takes 24+ hours pulling vacuum making tubes like they used to, that's the main reason most of the old ones are so much tougher.

I also like the sound of them better so it's a no brainer for me. I hunt for old tubes on the bay all the time as well as CraigsList.org and usually get collections in good shape from people gutting old radios and organs. Usually the tubes in those things are worth 10x what the whole thing is. I have bought these old radios & organs cheap (or free), swapped out the good old tubes for cheap new tubes and turn around & sell the thing for the same price I paid for them. Even giving them away, I get the old tubes for free. Watch tube auctions for groups of 4 to 12 tubes online and check out how many of them are from old organs. Tung-Sol (the real one), Westinghouse, RCA and GE made practically all USA made tubes prior to 1970 for all the organ makers in the USA and just relabeled them with their brands. Conn, Wurlitzer, Hammond and other tubes from these old organs are almost always extremely good tubes for guitar amps and will outlast anything you buy new.

The only new tubes I've found that take abuse well are JJs. They even survive in my VT40, which is just about the worst place to put cheap tubes on the planet. Plate voltages of close to 600V are normal in Ampegs, while Fenders putting out the same power are in the 475V range.

This is what my Ampeg does to Groove Tubes :: (they only lasted about 8 months)

Notice that not only is the printing cooked right off the tube, but the BASE is actually partially melted from the heat. This is in an amp that is running perfectly to spec with a bias nowhere near what would be considered 'hot' for an Ampeg. JJs are the only thing that can survive in this amp other than old 7027A tubes (which are nearly impossible to find and are serious 'BuxDelux' when you do).

Red Plate Special anyone? ancake:

To answer your question about 7025 preamp RCA blackplates, I say yes, they sound great in my Twin Reverb.
I don't think they sound $100 great so I use them pretty much interchangably with old GE 12AX7s that I find on auctions for about $15 each.

Cheers,
- JJ

 

[ZMAN]

I am not one to talk about tubes but yesterday I took my 2 month old 65 Deluxe back to the shop because I had a pair of Groove tubes go Microphonic. There was a Glassy tone from day one so my tech threw in a set of Ruby's. I know from nothing about tubes but they made a huge difference. The Can. price was 20 each and he replaced the first two. It was still under warranty. I am one of those what can remember tubes in televisions and I am amazed that technology in tubes is poorer today than in the past. I have heard this many times in the amp forums.

 

[kiteman]

I got an RCA 8343 (5751) from tube depot for around $20. I used it in my vj combo with a JJ EL84. Sounds real good.

Tube depot sent me an email asking how that tube sounded.

 

[Filipok]

These rare NOS RCAs are fetching more than $100 each! Even the new-in-box 12AX7As are super-pricey. Too rich for me right now, but if any fretters use them, do they REALLY sound that great? Can you tell the difference between one of these and , say….a $15 Tung Sol reissue?

Whether they are worth the premium price...well, that's another topic.

My rig has 5 12AX7s and 4 6L6GCs (run a mesa 50/50 and v-twin). Not patting myself on the back but it produces amazing tone. :bravo:

Just my experience here. JJ's tubes are the closest thing I've found to NOS. I've tried Groove, Sovteks, etc. and I have 9 tubes in my rig. When I plugged in JJ's that I bought from Bob over at eurotubes.com, the difference was tremendous. I've not had the stomach to cough up 50 or more for NOS tubes, but my good friend has a large stockpile of fabulous mullards, telefunkens, RCAs and GEs. I can tell you with 100% certainty that there is a noticeable difference in tone. Sadly, even the JJ's are about 70% of the most sought after NOS tubes.

So, I've been studying up on NOS tubes and am also going to start experimenting with them.

 

[kiteman]

I would say the JJs are a very nice compromise.