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In Reply to: Re: Anyone buy these 12au7 tubes lately? posted by Robert H. on July 23, 2002 at 07:35:55:
FWIW IMHO perhaps try a few other special types. For example, Mullard (UK) M8136 box plates or Brimar (UK) 13D5 or Mullard (USA) 5963....these all sound sweet and open.
Follow Ups:
Thanks
Hi SteveMy original draft response to your question appears to have disappeared into the ether. Very puzzling! Basically I suggested you try your luck with some of the more reputable US valve dealers.
Obviously I have some of those valves and other inmates may also, but all of us are justifiably forbidden to "sell" tubes here as this forum is not intended to be a marketplace. I have no intention of doing any "selling", merely assisting in the communal process of finding out more about the wonderful world of tubes.
But I surmised that if inmates wish to privately and discretely trade valves of equal value for the purposes of testing/listening/learning/enjoying without any money changing hands, then surely that couldn;t be a bad thing, could it?
In fact, you could email me at swculton@yahoo.com so we could discuss it further....
The M8136 box plate Mullard is a good tube if an early 1960's version - the very common 1970's version is a pretty dull affair, rumored to be made in China and assembled in the UK - and fakes abound.1ED5 is a date code, not a tube designation. Brimar m,ade many variations of the 12AU7, again, later ones were imported and not made in the UK. Mullard never made a 5963, if one is so labelled, it is likely an RCA or GE, again - eraly ones are vastly better.
Hi RobertI have several pairs NOS Mullard genuine UK M8136 CV4003 box plates with etched production codes such as "631" over "R8J4" and "R6L1". Perhaps either yourself or another resident toobaholic might shed some light on where and when these were manufactured? (I have seen enough Chinese tubes to recognise fakes and my tubes were sourced initially by the Australian Air Force way back when.)
My information is that in fact there were limited edition special 12AU7 types made by Brimar including 13D5 and 13D8 (my friend, a tube veteran, has the official factory documentation to prove it.) I have heard the vast sonic improvements this particular type renders in audiophile gear. Sadly I have but one genuine UK spare NOS pair left over.
On the 5963 front, as I mentioned earlier, the Mullards I have are USA manufacture (probably late 60s Sylvania or RCA), and deliver a clean, detailed sound which most audiophiles will probably like.
In general though, FWIW IMHO, amongst all common miniature dual triodes, ordinary low-cost 12AU7/ECC82 types tend to cast a dreadfully bland, uninvolving sonic character. In all cases where better engineered 12AU7 types are substituted, sonics skyrocket. Well worth seeking out and investing!
spindrifter
As FatBottle states, if it's an 'R' and not an 'r', the Mullard plant at Mitcham, UK.'63' is the tube code for VX8136C and the 1 is first variation.
Bottom lines are 'R' for Mitcham, 8 and 6 are either 1968/66 or 1978/76. 'J' is October, 'L' is December and the 4 and 1 are weeks of those months respectively.
I have a pair with pin guards/newer logo and the printing on the tube, which somewhat matches the acid codes (631 over R7G3,) is 77/40, so 1977 in the 40th week. The acid codes say third week in August. Close.
Mullard went to a 4 character lower line in the 60s, so that rules your tubes out from being made in the '50s.
As for your mystery Brimars, I have a pair of side D-getters with clear tops. Different in construction than the RCA ClearTops. I can barely read the acid etched codes, which appear near the lower part of the flashing and are on one line. Smaller type than the Mullard/Valvo/Philips codes. I think I see three characters then a slash symbol and then 1571 or 1671. I just can't tell. Anyway, they sound nice and I don't see them listed too often.
Hi ChrisThanks for your insights. Agreed, it's the **sound**" that matters after all. IMHO certain genuine Brimar bottles can tend to be unfairly dissed by so-called experts relative to, say, similar other UK offerings.
Fatbottle has asked in relation to presence and type of shields and I've answered below. Chris, do your M8136s have shields?
no splatter shield, just a thin copper wire connecting the round getter over the top of two mica spacers. There does appear to be an additional thin piece of mica plating laying on top of the main mica spacer.These have wide grey box plates that have three ladder rungs across their width. Mine came in the tissue paper/corrugated cardboard wraps and the white Valve Eletronic boxes that many of the Brit tubes come in (Canadian importers?)
Hi Spindrifter ,
You saidR8J4
R6L1
...for the etch codes . Ok , what type of shield do the tubes have ? Old , new (small) or none ? No doubt these were made at Mitcham , UK .
Robert:I have seen hundreds of CV4003 , tested them and I doubt the British military would ever get a cold-war enemy involved in any way with manufacture for their valves . They are far too consistent in appearance and electrical spec , most of these were the later ones too . I think you may be thinking of GEC who outsourced parts from the Chinese for the very last KT66/88 run .
Hi FatbottleAll these Mullard M8136s have no shield between the plates.
Hi ,
Not inside the tube , I was talking about the logo inking on the outside . Does this have a large 'shield' shape with 'mullard' in the middle or a small 'shield' shaped outline ? Failing that it must have something like '000-4003 KQDD/K 84-36' printed on it . Chris is correct about the '631' part of the etch , this does indeed refer to a M8136 . The date codes are sometimes confusing , the logo usually gives the game away though .Usual Disclaimer Applies:Unless of course the tubes are relabelled which I have seen quite a bit on ebay lately , of course they are M8136 but not from the best production runs!
Check the bottom line to be sure.As for the shield, mine has the 'newer logo' which is an "M" with a chevron at the bottom, making a boxy looking thing. These are probably the most recently producted Mullards, before they packed up shop.
Crikey, FB, I took your question literally!Internal shielding is a technical talking point with many toobaholics. As an example, consider the multiple variants of the humble 6CG7.....
These M8136s have "a large 'shield' shape with 'mullard' in the middle", as you put it. Most have "CV4003" stamped next to "M8136", a couple only have "M8136" without "CV4003". All have BVA logo as well as "MADE IN GREAT BRITAIN".
Are you suggesting these are likely to be from the 60s or 70s? IYHO which sound better and why? TIA.
spindrifter
BVA logo means nothing , easy to find Brimars and Mullard marked 'foreign' that still had the BVA mark . I guess this just meant that the manufacturer was a member of the BVA and adhered to BVA quality controls . If they're old shield (and not bought from bugleman) they will be 1960s most probably . Chris mentioned that the 'M' shield type was the last produced . This is in fact incorrect , the last ones had no shield at all , simply the NATO stocknumber and datecode . Do a search of Ebay for Cv4003 and you'll see some with the NATO numbering in there somewhere . Quite frankly the later ones test very well with close matching (I have tested hundreds of the things for customers , it gets boring getting a CV4003 out of the factory case then testing it , then wrapping it back up , they all test the same with only a small imbalance!) but the sound from the old shield types is preferred , I believe . Mullard made these CV4003 up until 1986 , only the special quality types seem to have been UK made though , it appears that standard 'domestic' Mullard EL84 and ECC83 I have seen that were 1980s production were made in India . Prudent question : Anyone out there with a 10M Mullard that can let us know the codes . I'll be surprised if these were UK made
hi allHow do you spot fake ecc82/e82cc etc..
i have a some collection of mullards ( saved from parents loft) as well as a couple from ebay and shops all of which i fully believe to be the real thing.
but how do you spot the fakes?
The 'fakes' I mentioned are not fakes as such but relabelled late production . I recently did an 'ask seller a question' on ebay regarding some E88CC/Cv2492 (I'm not naming the culprit , we all know who he is already!). These had the flat dimpled disc getter as per late 1970s production but the valves had an old 'shield' logo as per 1960s (which would have had ring getter) . Dead giveaway really , the etches indicated that the valves were late production Cv2492 from 1975 . Also the seller had Cv4003 in what appeared to be fresh 'Mullard' boxes which did not look right at all , again a dodgy old 'shield'logo was printed on the glass . More than likely these were relabelled late production Cv4003 from the 1980s (nothing wrong with 1980's Cv4003 , I have sold hundreds with no complaint but apparently the older versions sound better) . Most valve faking seems to involve Yugoslavian manufactured valves (which use the old Philips/Mullard tooling so they look exactly the same) , then overprinting the glass . Many have been fooled ! Best always to check the etch codes with the seller first .
fb
where can you get info on the etch numbers?
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