When an I63 is an I81

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When an I63 is an I81

Postby Bazp on Fri Jul 31, 2015 7:45 pm

Hi All,

I'm new to this forum, but I've in out and around of 'proper' amps for a while now

A forum buddy of mine from Fretboard in the UK suggested VAF maybe the place to go to answer this question, so here goes..

I'm trying to identify a particular ECC83 I have - it's a Valvo branded Mullard with short plates, Blackburn 'B2' codes, halo getter and seamed glass

I63 I hear you say? ..it also has 'I81' or '181' painted in white on both sides above the flasher and it sounds nothing like the Mullard branded B2 I63 I have. It's really clearly painted, so it's not a 'smudged' I60

Searches have drawn a blank, so just curious whether any of you fine gents could enlighten me?


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Re: When an I63 is an I81

Postby Lyre-crunch on Mon Aug 10, 2015 7:52 am

Post a pic if you can. If it has Mullard codes it must be a Mullard. I have several Valvos in my collecction (ecc83, ef86) and some of them have I think a three character code printed on top. Tubes/valves are individuals, they can have slight differences in the standard electrical parameters and so on, even when they come from the same manufacturing batch. Each will sound slightly different, but a very big difference in sonic character is rare, and might because of some kind of defect. I know Valvo branded Dutch ecc83's a lot from early to mid 60's, mostly the I65 version, and about late 60's to early 70's often Mullards in addtion to Dutch production.
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Re: When an I63 is an I81

Postby JeffWest on Sat Aug 22, 2015 2:44 am

ECC83s (and others) branded for sale under certain conditions in W. Germany and some other W. Euro countries at certain times had unique codes like a "serial number" inked on top, for purposes of warranty. Materials included with the tube also carried the code. Thus those inked (not etched) codes on the top differ piece to piece, and have nothing to do with dates, version, or factory ID per se, although they're linked to the brand that's on the tube. You'll find versions of these on Telefunken, Valvo, Siemens, etc. Sounds like that's what you're referring to.

If it has genuine Blackburn "B2" code further down on the glass, per your description you can still expect "I61" there (if it's 1962 made, with copper grid rods), or "I63" if it's 1972, w/silver rods.

Yeah, different examples of Mullard 12ax7s even of the same type measuring similarly (and even of the same type made in the same month!) can sound significantly different in the same application. If you do a "shootout" swapping a small handful inV1 of yourfavorite amp the odds are good that you may find one or two that you seem to prefer over the others for some reason, at least that's my experience. Not limited to Mullards but I would say it's particularly true of Blackburn ECC83s.
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