Do yourself a favour and get some matched 60's NOS RCA 12ax7 tubes.
Regardless of audiophile jargon and such hardware ~ IMHO the RCA tubes go back so far and they "are good" - really good, they set the industry standard. They are a bit costly , but if you are patient you'll get a good deal on Ebay.
Cheers.
I have heard great things about the RCA's.
12AX7 Tubes in Stock
I found some at the above link. Except for the "butt ugly" ones, the matched pairs are out of my price range. Think I ought to try the "butt uglies" ????
Hey Jim,
Howdy doody !
Yes mate, go for the butt ugly ones, I've got several pairs myself.
They may not look like jewellery but if'n they be RCA and strong they'll get the job done much to your delight !
Don't forget , all new tubes need quite a few hours to "burn in" (run in).
Then, when you're satisfied and have a favorite set, then start experimenting with other brands- you can always fall back on the good'ns.
Hope this helps, careful not to go broke as I've been bitten and I've seen some 12ax7's go for thousands, (Rather absurd, but...)
One thing is definately needed ! ~ A JOB !!!
Cheers,
Andrew.
Me again,
I've been looking at the link you supplied, it is very informative - I have been there before.
Don't rely on just one source for tubes etc ... check ebay, there are many available.
Cheers.
One of the problems I am having is the shear magnitude of choices. Even limiting myself to only NOS RCA, they are tons of options. I just feel overwhelmed as to decide how to go on this venture. Not to mention that Mullard, GE and Genalex NOS tubes are also highly regarded.
Yes Jim, I understand full well the dilemma of making a choice.
And yes again, there are Mullard, GE, Sylvania,Raytheon/Baldwin,older Sovtek 12ax7LPS(long plates) & others, all of them are good tubes.
I try to stick to the rule of thumb that RCA were there before the others and I know for a fact (my ears) and the spooky looks from my Pink Floyd loving neighbor and the lack of complaints about the volume, bass punch, the shimmering glassy highs & crystal clear vocals (from other neighbors).
Hey man, I am hearing vocals so clear I can understand nearly every word, often I used to think the words were different
And the seperation of the instruments is almost to die for.... well.
I'm not saying you must get RCA the choice is yours,
Need more help ?
Cheers !
I heard back from A.R.T.
Hello Jim,
Either are fine. The specs in the manual say AX, but it's possible AT's were substituted. You can run either without harm.
I recall that a similar change was made in the ProVLA- it was designed and spec'd for AX7's, but after a few runs, we did some A/B listening tests and most of us thought AT's sounded better, so they were used from there on out. But the manual specs always said AX7, with the caveat "specs subject to change without notice" covering the difference.
I don't recall a similar change with the TubeEQ, but it would explain what you found.
So, what are peoples take. AX or AT ?
Hello Jim,
Either are fine. The specs in the manual say AX, but it's possible AT's were substituted. You can run either without harm.
I recall that a similar change was made in the ProVLA- it was designed and spec'd for AX7's, but after a few runs, we did some A/B listening tests and most of us thought AT's sounded better, so they were used from there on out. But the manual specs always said AX7, with the caveat "specs subject to change without notice" covering the difference.
I don't recall a similar change with the TubeEQ, but it would explain what you found.
So, what are peoples take. AX or AT ?
I went through a few of the 12ax7 tubes and 12at7. In the 12ax7 circuit (voltage amplification stage) use of 12at7 usually produces thinner sound - but it greatly depends on schematics - a lot of people, including myself, hate 12at7 in 12ax7 slot due to a squeaky sound it produces.
As far as 12ax7 goes, it depends on the sound you want to get at the end. Telefunkens will bring brightness and air; Mullards will bring midwarmth, but not as much details; Amperex is a middle ground between the two. If you want midrage shine try Mazda. My favorite is Sylvania 5751 gold brand - but it's very expensive. RCA with D getter and charcoal plates (as opposite to shiny) produces very good bass, very warm sound, but still has a lot of details.
Stay away from current production. They cost more than old stock, but have a mediocre sound. Example - current price for the aforementioned RCA is $30-40 on Ebay. With Genelax Reissue, you will pay about $39.
I'm bloging my experiences with tubes here. Hope it helps:
12Ax7 | Tube Maze
As far as 12ax7 goes, it depends on the sound you want to get at the end. Telefunkens will bring brightness and air; Mullards will bring midwarmth, but not as much details; Amperex is a middle ground between the two. If you want midrage shine try Mazda. My favorite is Sylvania 5751 gold brand - but it's very expensive. RCA with D getter and charcoal plates (as opposite to shiny) produces very good bass, very warm sound, but still has a lot of details.
Stay away from current production. They cost more than old stock, but have a mediocre sound. Example - current price for the aforementioned RCA is $30-40 on Ebay. With Genelax Reissue, you will pay about $39.
I'm bloging my experiences with tubes here. Hope it helps:
12Ax7 | Tube Maze
12AT7 Tubes in Stock
Looking at the above link, under RCA I see 12at7 grey plates for $50 per matched pair.
What do you think?
It seems the 12at7 are cheaper and more numerous.
Nice read. Thanks. By description, I am again leaning towards the RCA's.
the12ax7 RCA black plates look out of reach. I just wouldnt trust ebay for getting tubes. maybe I am silly. If I could find the RCA's you mention somewhere besides ebay for that price in 12ax7, I might do that.
What is the difference between black and grey plates?
So it looks like I may be down to these 2:
12AT7 RCA made Blackplate, "wing shaped" black plates, most square or D getter, OEM label or no label. 50/pair
SPECIAL: "BUTT UGLY" 12AX7 / 12AX7A RCA greyplate tubes!
60/pair
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5751 is a GE "Five Star" version of the 12AX7. It is electrically very similar to 12AX7, but with slightly less gain, more rugged internal construction, etc. It's not much like 12AT7. It's really more like a variant of 12AX7. One can almost always directly substitute a 5751 in a 12AX7 circuit, but again, the gain (mu) is a bit lower (5751 mu = 70, 12AX7 mu = 100).
12AT7 is a quite different tube, with lower rp, higher gm, less gain (mu = 50), etc. You can put a 12AT7 in place of a 12AX7, but now you're into modification territory, and the circuit will now act very differently from the original.
BTW, does this ART EQ use the 12AX7 like the ART guitar effects boxes do? With a really low plate voltage, to "warm up" the tone? If so, there ain't nuthin' even remotely "hi-fi" about it. Worth checking into.
--
12AT7 is a quite different tube, with lower rp, higher gm, less gain (mu = 50), etc. You can put a 12AT7 in place of a 12AX7, but now you're into modification territory, and the circuit will now act very differently from the original.
BTW, does this ART EQ use the 12AX7 like the ART guitar effects boxes do? With a really low plate voltage, to "warm up" the tone? If so, there ain't nuthin' even remotely "hi-fi" about it. Worth checking into.
--
I was just exploring the idea. The manufacturer seems to feel 12ax7 and 12at7 work equally well in this unit. So, I was thinking maybe 5751 would put me in the middle so to speak.
As far as how "hi-fi" the unit is, I find it very musical. I cant answer your question comparing it their guitar effects boxes.
But I will say that in time, I may shelve it. Hence, the reason I dont want to spend BIG money on new tubes for it.
I can say also that it sounded fine with a 12at7 in it. And at that, with a rather inferior modern day tube in it.
So it seems to me, just about any tube thats been recommended here so far would be a improvement over what was in it since:
1) the 12at7 isnt very popular around here
2) NOS tubes are everyone's preference
So whether I got a NOS 12at7 or a NOS 12ax7, or a NOS 5751, all would be better than my JAN Philips 12at7 non-NOS, right?
This thread HAS convinced me to go NOS
12AT7s are popular around here in the right places. I highly recommend the Mullard CV4024 in a spot that can use 12AT7s well. Jim McShane just got a bunch more in stock, for $64.50 a pair or $31.50 each. Why is a pair a little more than 2x the single price? Mainly because he devotes time to do thorough testing and matching. You won't always get that from many other vendors, and the prices are still pretty good.
I replaced Sylvania gray plate 12AT7s with the CV4024s, and the difference was subtle but noticeable -- better definition and lower background noise ("blacker between the notes," if you will).
As far as 12AX7s, if this application is for anything requiring low noise or microphonics, I'd suggest giving the Sovtek 12AX7-LPS or other long plate tube a try. I compared these to a set of RCA gray plates with the volume cranked and inputs open but with no active signal (i.e., phono cartridge at rest) and the -LPS was much, much quieter. (Granted, both of these sets were well used at this point.)
Jim also has the new Mullard reissue long plate 12AX7, which are reported to be quiet, too. I hope to try them soon.
Jim's tubes page. (Do a simple page text search in your browser to locate the tube types.)
Hope this helps. It seems like you have a lot of flexibility in this device, especially if the designers are open to changing how they supply it to customers. Personally, I'm not sure that's a good thing, unless it really is intended to color sound.
--Jeff
I replaced Sylvania gray plate 12AT7s with the CV4024s, and the difference was subtle but noticeable -- better definition and lower background noise ("blacker between the notes," if you will).
As far as 12AX7s, if this application is for anything requiring low noise or microphonics, I'd suggest giving the Sovtek 12AX7-LPS or other long plate tube a try. I compared these to a set of RCA gray plates with the volume cranked and inputs open but with no active signal (i.e., phono cartridge at rest) and the -LPS was much, much quieter. (Granted, both of these sets were well used at this point.)
Jim also has the new Mullard reissue long plate 12AX7, which are reported to be quiet, too. I hope to try them soon.
Jim's tubes page. (Do a simple page text search in your browser to locate the tube types.)
Hope this helps. It seems like you have a lot of flexibility in this device, especially if the designers are open to changing how they supply it to customers. Personally, I'm not sure that's a good thing, unless it really is intended to color sound.
--Jeff
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If you are against Ebay - which is hit and miss; although I got some fantastic tubes from there, you can try: thetubeshop. Steve there is very helpful and has some superb deals for the RCA 12ax7 with D getter. Currently he has 5 black plates and 3 long gray plates - both are superb. The price is $35 for black and $30 for gray. Really hard to beat the deal. I ordered tubes from him in the past and although used, they were incredibly strong and very high quality. He might still have 5751 RCAs (for $35), which are superb tubes. Send him an email (I'm in no way affiliated with the tube shop). You will be blown away by the sound.
All help is welcome
The Mullard is under consideration. I did read that some find them a bit to prominent in the midrange. But like any internet blog read, you dont the the system, the device, the listeners preferences, the speakers, the room, nothing. So a comment like that may or may not be what I would hear with them.
The unfortunate thing here for me is that I need to get this right the first time. Obviously, the the folks that will try a half a dozen pairs to find the right fit have more disposable income than I. Whatever I get, its what I will be stuck with for a good long time.
If you have read this entire thread, you know that its unclear exactly what is the right tube for my ART tube EQ. So this has complicated things.
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