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I have had it! I purchased a bunch of long plate grey and black 12AX7s from a reputable dealer and 2 of them have died (no signal at all - the grey long plates) and one has become microphonic (the black long plate)
This is bugging me and now I am down tubes - and this is from a MX110 and an MC240. No other tubes are gone and I recently had the MX110 checked out due to a leaky capacitor. (both these have been rebuilt)
I am fed up here. These weren't cheap of course and I just can't understand why two went dead and the other microphonic. I believe there have been another that went microphonic (a black plate rca) some time ago. I refuse to divulge the name of the dealer because I don't want to screw with his business and to be honest, perhaps it was my fault for not purchasing the true NOS tubes instead of those that may cosmetically may have been challenged.
What currently available will give me great results, and I am looking for warmth and soundstaging and depth. Not a detail freak and also don't mention the Gold Lions...they sounded brittle to me. I am running these into a set of Tannoy Monitor golds so they need to be preferably on the warm but not dead side.
Sorry for the rant!!! It does feel better!
Paul
Follow Ups:
I think I know the dealer your referring too. His definition of "used, test excellent" and mine differ significantly.
I have many pairs of RCA long black plates. They are one of my favourites. I have never had a pair die or become microphonic. I'm sure it happens eventually, but if it happens to you regularly with tubes you get from this dealer than you are not get quality tubes.
Don't blame it on RCA.
Maybe something weird about the MX110.
I had one in the 80's.
New Mac tube gear, MC275, C2500, no problems at all, 3.5 years.
Mac gear is reportedly easy on tubes from that vintage. Perhaps it is the tube's fault?
Paul
The RCA tall plate are a shame they go microphonic or are noisy. I had too many noise issues with NOS RCA 12AX7 tall black plate. The black plate just do not last long with regard to noise.I find no difference in sonics with NOS RCA 12AX7 tall grey plate. Few are noisy. I would not even consider any RCA 12AX7 used tube.
I did not care for Genelex reissue, but my amp is very revealing to 12AX7 preamp tubes. The amp is ultra clear sounding. Anything less of an amp limits the 12AX7 performance as the tube sonics become slightly smeared over.
Edits: 12/22/16
Jim
I find that same thing with my RCA black plate 12AX7s.For some reason,my Raytheon black plates don't seem to have as much of an issue with microphonics on the 12AX7s.
They RCAs really do sound nice tho and I still keep them for amp drivers as they don't expose it so much like they do in a preamp.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Yes Michael, the RCA 12AX7 tall plate are great. You hear any difference in-between tall black plate & tall grey plate?
If I may ask, what was it about the Gold Lion you weren't a fan of and what were it's strong points in your system?
Paul
The Genelex sounded more ordinary vs the RCA that had more black in-between instruments and the singer(s) voices. Just a better soundstage & clarity.
My amp is DIY with triode connected PPP 6V6 tubes. I built same amp with PPP 45s and like the 6V6 amp better.
The 12AX7 was in the preamp position. The triode 6V6 was more lively sounding. Frankly, the amp is best I ever heard. I owned a lot of upgraded vintage amps.
I would be willing to bet the Genalex' softer top end is what you heard. It is quite often described in different terms, but "clarity" is usually a product of top end extension/energy.
That's why I like the Genalex/Tung-Sol combo - the two tubes have performance attributes that compliment each other very well.
Just my $0.02 anyway...
Keep in mind, a tube can be display microphony in one application or chassis, and be fine in another.
I've read papers on microphony. I'll have to look again to see if they explain what would make a tube turn that way. They certainly explain why it may be there from the get go, or just why its inherent in the tube type itself (construction).
"I can't compete with the dead" (Buck W. 2010)
"$45 gets them out the door tomorrow. $50 gets them out the door yesterday" (Byrd 2016)
That is not to say you should not buy them. I buy used tubes all the time. But i just get them with the understanding that they might not work out or be microphonic, etc.
No offense about your choice of 12ax7 and rca makes great tubes, but their 12ax7 is most coveted by musicians for their guitar amps and tone production.
For your MX110 the original 12ax7 were Telefunken. So for the making your preamp authentic would require a fair bit of expense.
are you talking about the GL B759? I'm using them in my Sherwood and they sound every bit as good as my RCA long black plates.
If you're popping tubes you have an electronics issue going on there. I had a PAS preamp where a voltage regulator on the power supply board would go (like clock work I might add) and take out an expensive vintage NOS 12AX7. And like you they were vintage hard to get tubes - and now they're gone!!!
I am talking about the one I am using. Interesting tube. The MX110 came back from the shop about 2 months ago and there is no weird behaviour with it. It was a restoration by Richard Modaferri and the 240 was the restoration done by myself and another tech who checked over the work.
Paul
It would be a good idea to have the tubes tested for transconductance. Also, did you get test values when you bought the tubes? That would be a clue as to expected lifetime.
Also, how long were they in use before they "died"?
Do you know if the tech checked for coupling cap leakage in both of your pieces of gear?
Steve M.
The tubes had measurements and also I have a tube tester here (Stark 9-66) so I was confident that these were cool. The tech went over the MX110 where most of these failures had occurred and the other can be taken to a tech but nothing working out of spec to my knowledge. The 110 had a power supply cap leak at one point so I figure that taxed the tubes somewhat. But I wassn't stupid. I soon turned the thing off and then took it in!
I suppose this could be a two part thread however....basically I am wondering if one could get away with new production input tubes such as the 12AX7 (note - no other input tubes have been affected in this way in both units) and my answer from two people was Mullard 12AX7 reissue and the JJ ECC803s as recommendations.
This is gonna be interesting as I went all RCA long black and grey plates for a while and although they are warm, they also have a degree of brightness on top that I can still hear...
Paul
I've been very happy with the JJ803s. They make two versions. One version with bright shiny steel/chrome pins and another with gold pins. All my experience is with the gold pin version. Also, FWIW, JJ's 5751 is superb tube.
I have some JJ ecc803's which I bought some time ago. What I remember is a really good tonal balance with good bass. IIRC the JJ803 was soposed to be a copy of a SIEMANS tube. BTW mine were just the steel pin!
Some coupling caps maybe passing too much DC. That'll make tubes get noisy, go microphonic, and die more easily.
Recently checked and it happened in two pieces of gear. I think it's reliability here that is the issue.
Paul
from amps which I've worked on (and ppl want TFK or some such replacement tubes). Many, many test very high and are quiet.
I'm surprised at your experience. Maybe, the tubes were rejects.
They were high and quiet. These are part of a scratch and dent sale that is on the site. Those of you who are guessing, keep the name of the organization to yourselves. I don't wish to get into a war about it with the vendor.
Just too coincidental. Interesting that a new set of tubes a friend of mine bought (also RCA blacks) tested great but lesser than what was stated on the package. This was by my techs...)
Anyway...not to worry. I am looking for alternatives in the rational current production world.
Trying out a Gold Lion ECC83 in the single position in the MX110 and in that application it doesn't sound half bad compared to the long grey plate 12Ax7...
Paul
Talk to AA sponsor Jim McShane about culled "reissue" Mullard specimens. Plenty of warmth, there.
Eli D.
What do you think of them?
How do they compare to say the long plate RCAs?
Paul
RCA is known for "chime". Mullard, even "reissues", is known for midrange accent. FWIW, I like a RCA/Mullard mix, but it's not always doable.
Eli D.
Given what Eli said concerning the sound quality of Mullards and RCAs which I thoroughly agree with . I am surprised you haven't sought the older Mullards. You seem to like warm sound and they are hard to beat. Yes you may experience a tired tube again but use your approach i.e reputable dealer who accepts returns.
BTW I use 5751s whenever a circuit will work with it. That is topic or stuff for yet another thread.
Expense is why I haven't found them. Telefunken 12ax7 tubes are easier to find up here for some reason.
Paul
FYI, I find the current production equivalent of the RCA/Mullard mix is the Tung-Sol ECC803S or 12AX7/Genalex B759/ECC83/12AX7 combo. It is a VERY good set of tubes!!
Interesting you should say that! So I assume you are saying the Tung Sols are RCAesque and the Gold Lions are Mullardlike or is it the other way around?
How do the reissue Mullards fit into this?
I have bought from you and also redone my MC240 with your upgrade so I do trust your opinion on this!
Thanks Jim!
Paul
Edits: 12/21/16
The Tung-Sols have a bit of the same "chime" the RCAs do/did; and the B759 Genalex has a tone quite similar to an old stock Mullard or Amperex. They get along quite well.
The reissue Mullard long plate is fine - but it really has a very narrow point in the marketplace. The Genalex kind of took the "warm" market, and the Tung-Sol (and in some applications - like phono stages - the 12AX7LPS Sovtek) took the "livelier" market.
Thanks for that Jim!
Just for my benefit, could you tell me what you hear as the difference between the Mullard reissue and the Gold Lion B759?
Paul
The B759 is quieter with its spiral wound heater; and it has better tone all the way up and down the spectrum.
The latest production B759s also have lower microphonics and noise than the earlier production from a few years ago.
Jim, I may have heard the earlier first run Genelex 12AX7. My ears are falling off sensitive wise on high end frequencies. I heard to 12000Hz. My amp is unique and tubes sounds different in different amps.
Based upon your experience the Genelex may be as good as any vintage tubes. But my unique circumstances the RCA worked better for me.
You would definitely prefer a tube with more top end energy than the Genalex, no doubt! Depending on the circuit you may find it works well in conjunction with other "brighter" toned tubes.
I'm 65 years old (yikes!) and I'm definitely aware of my own hearing limitations also. The advantage I DO have is I get lots of feedback from customers and that allows me to have a pretty good idea of how tubes sound to people besides me.
I thought you found the current Gold Lions to sound brittle. I had never heard them described that way, but more warm than anything out there excepting the old English tubes. Your system seems to be a warm one, and despite my own inveterate tube rolling activity, I am surprised you need to coax much more warmth out of it.
A long time ago I bought a pair of old GEC 12AU7s they tested very low. They sounded great however and despite their failing status at this point, they still sound superb. I used them sparingly.
I thought at one time that they sounded a bit bright. I don't know if brittle was the descriptor (perhaps it was, it's been a while)
I would like a comparison between the GL and the Mullard reissue however. Especially if they have tried them in a McIntosh but that's not really essential.
I suppose I am looking for a new production tube that does some great things without calling much attention to the upper midrange. I am surprised that the GL in tandem with other tubes is behaving in a totally different way to which I have heard.
The plot thickens...(for me at least!)
Paul
I obviously do not know your electronics. Perhaps you should use all B759s where possible.
I have never found the b759 bright. If anything well balanced with a very nice midrange. Like I said, very much like a great!! vintage tube.
Well it's a McIntosh MX110 pre going into an MC240 amp (6L6GC tubes in output) into a pair of Tannoy 15" Monitor Gold speakers. So the horn driven aspect of that kinda means stay on the warm side of the street!
Paul
I'll second the B759s as sounding reminiscent of a great vintage tube. Only new!
Interesting about the RCA chime and the Mullard midrange. \\By midrange, what area of frequency boosting is this being done in?
I know this is also asking for a bit but how do the JJ ECC803S tubes currently fitting into this equation?
Paul
Edits: 12/20/16
New tubes can be microphonic. I does not show up on most testers, either. You have to put them in a circuit. A reputable sellse should accept returns, though.
I agree about the return bit. This seller has a 30 day warranty
I know new tubes can be microphonic as well but it just hurts when almost $200 worth of tubes die and they are from one particular source. Plus perhaps it's just that this late in the game, RCA 12AX7s may be suds that are showing up.
Paul
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