Mullard / IEC 10M Master Series

They're worth more dead than alive.
Seriously, I suspect they're very good (tight specs, tolerance)
Their value has taken on a life of its own to collectors.
Being how they're in hand anyway, try them.
I doubt virgin fairies are going to dance on your speakers. Honestly i hope I'm wrong :dunno:
 
As far as I can tell, they are absolutely NOS. Can’t believe I found these. Any concern that they are labeled IEC rather than Mullard?
 
they are the same tubes off the assembly line that have been subjected to a stringent selection process. The special packaging was the way that Mullard used to distinguish this. During the later part of the golden age of tubes, the idea of having a "special quality" line became a selling point. Thus you had Amperex 'SQ' tubes, Sylvania had Gold Brand, Mullard 10M, RCA 'Command', GE 5 star, etc.
 
I used to have some, used some of them and then sold the rest. I would say they were the best 12ax7s I've heard, with the possible exception of the nickel-plate Mazdas. Better than smooth or ribbed Telefunken, regular Mullard, RCA etc, as always in my opinion and in my system.

I think I can't mention figures here but I'd characterize the money my quad brought as "stupid".
 
I think I can't mention figures here but I'd characterize the money my quad brought as "stupid".

Haha - well, I’ll most likely keep them. I’m thinking about using them in my phono preamp. Actually? I probably need to buy a new phono preamp.
 
IEC was the Mullard importer in the USA. They could mark any tube they sold as Mullard, it was legal as they "were" Mullard in the USA.
 
The later vintage, IEC/Mullard 10M boxes, with full golden color boxes, may actually have different brand tubes, relabelled. The original 10Ms, as shown in the OP's pics above, in the blue-purple/golden boxes, should indeed have Mullard made and tested, small plate (14mm tall) ECC83s. The OP's first pic of the tube does show a B---- code etched in the glass, confirming Mullard Blackburn plant manufacture. Some of the genuine Mullard tubes have lightly impressed letter/number codes, but they usually do have a two line code. Note that a four digit Mullard date code line signifies a '60s or '70s made tube, while a three digit date code will confirm 1950s manufacture.

Speaking of 1950s Mullard manufacturing, it is probable that 1959 was the last year of large plate (17mm tall) tubes. Small plate ECC83s can also be found with 1959 date codes. I believe the 10M 12AX7/ECC83s were only available as small plate tubes. Everyone should have no doubt in their minds that genuine 10M tubes of any vintage were special, tested and selected tubes. They have been and continue to be highly desirable, coveted tubes for their audio quality.
 
You are definitely correct ! There was an old thread about the 10Ms on another site which had posters doubting their sound quality or long term usage was any different from "normal" small plate Mullards. While we can all vouch that small plate Mullard, Amperex, Philips et al ECC83s were/are excellent performers, the 10Ms were guaranteed for 10,000 hours !

Now, today, I can vouch for some small plate and large plate Mullards which have easily lasted that long length of time. 40 hours a week, at 50 weeks a year is only 2000 hours. So, imagine using these tubes during a "typical" work week, for five long years, without any noise or microphonics or duds. Try that with the Sovteks and let me know the results, please....

So, if you are a musician or audiophile type, who worries about a tube crapping out over time, the 10Ms could be your "guaranteed" choice. However, where can you redeem the IEC guarantee, if needed ? LOL ! While I am certain there are "collectors" who "stockpile" the 10Ms and any original Genelex 12AX7s they can find and get, these tubes will eventually be used and listened with, hopefully....
 
You are definitely correct ! There was an old thread about the 10Ms on another site which had posters doubting their sound quality or long term usage was any different from "normal" small plate Mullards. While we can all vouch that small plate Mullard, Amperex, Philips et al ECC83s were/are excellent performers, the 10Ms were guaranteed for 10,000 hours !

Now, today, I can vouch for some small plate and large plate Mullards which have easily lasted that long length of time. 40 hours a week, at 50 weeks a year is only 2000 hours. So, imagine using these tubes during a "typical" work week, for five long years, without any noise or microphonics or duds. Try that with the Sovteks and let me know the results, please....

So, if you are a musician or audiophile type, who worries about a tube crapping out over time, the 10Ms could be your "guaranteed" choice. However, where can you redeem the IEC guarantee, if needed ? LOL ! While I am certain there are "collectors" who "stockpile" the 10Ms and any original Genelex 12AX7s they can find and get, these tubes will eventually be used and listened with, hopefully....
There are also incidences of unscrupulous sellers who faked the '10M' on the bottle. I am sure i have seen a few on the bay where the printing just did not look right. You always need to be sure of what you are buying if you are going to shell out big bucks for a supposed SQ tube. There are guys who can easily gold plate pins and make up fanciful stories of how special or rare their tubes are when in actuality it is all BS. One notorious seller has changed his epay seller's name because of all the negative publicity posted on audio forums. PM me if you want to know who this person is.
 
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In speaking with the person I got these from, he says he found them at an estate sale. Probably paid a few bucks for them. I paid very little - nowhere near the going rate for these. I was able to snag 2 of the 12ax7a and 1 12au7a.
 
I read somewhere that the regular pins signifiy “Concert Series,” while gold pins mean “Master Series”
 
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In speaking with the person I got these from, he says he found them at an estate sale. Probably paid a few bucks for them. I paid very little - nowhere near the going rate for these. I was able to snag 2 of the 12ax7a and 1 12au7a.

I'm gonna have another beer..................................:mad:
 
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