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A question for the knowledgeable.
Were the iconic Mullard 12AX7 10M tubes specially made, or just regular production stock selected for close tolerances, low noise, balanced triodes etc.
The examples I've seen are coded I63 which is the common short plate tube manufactured in & after 1965.
Most importantly do they really sound any better than a well balanced regular short plate Mullard?
I recognize that 10M tubes claimed a 10,000 hour life with a two year warranty, came in elaborate packaging & some had gold plated pins.
But perhaps this was a marketing strategy, a case of more style than substance?
I mean no disrespect to those who own & treasure these tubes; I simply would like to understand if there is a real definable difference between the 10M & normal Mullard production of the same era.
I have some yellow labeled Mullard ECC83 (coded I61) which sounds really sweet, & question if the 10M would be an upgrade?
Any thoughts, or experiences with the Mullard 12AX7 10M, would be appreciated.
Best Regards.
Follow Ups:
Agreed. Marketing. I wish someone would produce some kind, any kind, of evidence of any of these specially branded tubes somehow being special or different - Sylvania Gold Brands, IEC 10Ms, Philips/Amperex SQ/PQ, GE 5-Star, RCA Command, National Goldline, Westinghouse Gold Star, whatever. I bought a lovely piece of literature some years ago that was issued by Sylvania about the GB tubes. Nothing specific about any tube or tubes was mentioned.
I've got some 10Ms, and they're RFTs. Lovely enough tubes. I like the RFT ECC82. These don't sound, test, or last any differently from a non-IEC 10M branded RFT, though.
No matter whether a tube is specially selected from an assembly line, or even constructed differently, can the final sonic performance be guaranteed by this selection, grading, or construction? The Genelex data sheets that come with some of the tubes are lovely, but what kind of "improved" or "better" performance do they guarantee or reveal whether there's something different going on in the bottle.
- SJ
Current inflated prices is not an indicator of past manu process. Good example of that is recent "pinched waist" tubes being bought at high levels and they weren't even PW types. If Mullard actually had a separate process to build tubes with different recipes than normal production...then great...but lets see the proof!
jstrm
I agree. Nothing personal Interstage Tranny but there is a lot of hype about 'special' tubes. Marketing has been around a long time.
P.S. I like Mulard small signal tubes.
I Have used Mullard 12AX7 and 12AT7 tubes in my Mcintosh Amps for the past 40 years. They all gave me 10,000+ hours and sound wonderful. Have used them in my Michaelson & Austin tube amp and McIntosh MC-275 amp as well as McIntosh C220 preamp. Chinese tubes have lasted less than 2000 hour in most cases. Old RCA tubes have also give me long life. Mullards are wotrh the money and are truly reliable compared to many current day tubes.Hope this helps.
Edits: 06/26/12
Hi have both 12ax7 and 12au7 in 10M series. They are good tubes for the year of production, but I wouldn't call them special. Very dynamic, very fast, very transparent - but so are a lot of tubes from the same time. If you compare them to Long plates Mullards or Amperex from 1950s, they definitely don't provide a unique sound you would pay a lot of money for.
Mullard 10Ms might not sound special to you, in your systems, but they are definitely very special tubes.
For a manufacturer to guarantee a tube for two straight years and design for a 10,000 hour life, the gold pins are not a simple decoy. These tubes are indeed very special and commanded very stringent manufacturing tolerances. At the same time Mullard made these 10M tubes,(not the late '60s early '70s IEC branded tubes), Mullard also offered laboratory matched pairs of output tubes with a simple 90 day warranty. Obviously, to suggest we could use these 10M tubes for 24 hours a day, 365 days a year, guaranteed for two solid years, in studios and sound reinforcement duty, these have got to be special tubes. Do the math and then you will say wow ! 8,760 hours over two years, which would not be uncommon in a 24/7 sound studio during the magical tube era, is quite a guarantee.
1000 hours a year represents something like 20 hours a week for 50 weeks. Ten years of this for 10,000 hours is quite a feat. Now, many of us know that vintage Mullards, both small plate and long plate, can last decades; easily. But, have we or the former owners of these classic tubes listened with those tubes for 4 hours a day for 50 weeks a year, ten years in a row ? I doubt it. The fact that Mullard specified great specs, like low noise, for 2 solid years, designed for 10K hours, these 10Ms must be special.
If you watch the prices on epay, 10M ECC83s, all small plate BTW, fetch some crazy prices; new or used. The end-user buyers are thrilled to score these tubes. These tubes are definitely not simply manufacturer tested pulls with gold pins.
Concerning their sonic value, they do sound like typical small plate Mullards, at most listening levels. However, step-up the gain to mic preamp or guitar amp overdrive usage and you will undoubtedly realize these are special low-noise tubes. These days, finding matched pairs of even good used ECC-83 or ECC-82 10M examples is quite a pricey expenditure.
I think that you are wrong, but wont make any definitive comments until I know for certain. I have seen nothing to suggest that 10Ms are any different than regular production Mullards in terms of life or internal construction. They do seem to test a bit better and also tend to be a bit quieter, but I think this is just the result of selection. I have sold, listened to and tested many Mullard 10Ms. Mullards are probably my least favorite European made tubes for audio, so Mullards never stay in my circuits for long, but I have given them many chances.
It's going to take more than the word "must" and some simple math to convince me that these were actually non-production tubes.
Show us some published info straight from the Mullard factory.
Current inflated prices is not an indicator of past manu process. Good example of that is recent "pinched waist" tubes being bought at high levels and they weren't even PW types. If Mullard actually had a separate process to build tubes with different recipes than normal production...then great...but lets see the proof!
jstrm
10M was a trademark of IEC who distributed Mullards in the US . 10M were just selected Mullards just like the Genelex Gold Lions
Al
Yup! My guess is that they are the exact same tubes as other production just tested to a higher standard. I also require proof.
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