Philips 12AX7 ECC83 found in amp...

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Philips 12AX7 ECC83 found in amp...

Postby BIG Dave on Sun Oct 04, 2009 4:04 pm

I recently bought a JCM800 2204 (vertical inputs) and when I opened her up, I found three preamp tubes marked:

PHILIPS
12AX7
ECC83

There is a raised seam across the top of the tubes.
The codes are all the same on them:

2A1
05E

The first character on the second line is not a perfect zero, it actually appears to have a vertical line through it. Can anyone decode these six characters? I was hoping to see I6* but no such luck...

BTW, the output tubes are marked RCA 6550. I usualy prefer EL34 over 6550 tubes however these sound pretty good in this amp so they may stay for now.
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Re: Philips 12AX7 ECC83 found in amp...

Postby PeterS on Sun Oct 04, 2009 5:02 pm

According to a list I printed from the Triode Electronics site, O with a line through it (like Greek letter phi) means Mullard Whyteleaf, Kenley, UK.
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Re: Philips 12AX7 ECC83 found in amp...

Postby Dai on Sun Oct 04, 2009 10:29 pm

the 2A1 is Ei Yugoslavia. Should really show pics for tube ID threads to be certain.
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Re: Philips 12AX7 ECC83 found in amp...

Postby BIG Dave on Mon Oct 05, 2009 12:16 am

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Re: Philips 12AX7 ECC83 found in amp...

Postby Dai on Mon Oct 05, 2009 3:49 am

yup Ei. For those note the top seams, internal structure (looks like a smooth plate Telefunken but unlike a Tele doesn't have the silver "horns" on top of the plates. Plus the code. Brand could be all sorts--Telefunken, Siemens, RCA, Philips, and who knows what else. Later ones have silver plates (might actually mean less quality of the plate material but don't quote me on that). Also seen some with (apparently aftermarket) gold plated pins which I see as just a ploy to make them seem more special than they are (and charge accordingly). Seems to be general agreement that they are pretty good sounding but often too noisy for input stage use (microphonic ones can be used in other positions). Apparently not long lived.

edit: what you put as "O" from the bottom part of the etched code (which is some weird looking character) is the factory code. The top three, I've seen "2A1" and "2A3" (IIRC). Could be others.
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Re: Philips 12AX7 ECC83 found in amp...

Postby BIG Dave on Mon Oct 05, 2009 5:10 pm

Okay, they're Ei. Thank you Dai. What I don't understand is this webpage: http://www.audiotubes.com/mullcode.htm . It references the zero with a vertical line through it as the 'Mullard Whyteleafe “B”’ (Kenley)' factory (last white table, 6th row from the bottom). Is this webpage incorrect? Thank you again!
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Re: Philips 12AX7 ECC83 found in amp...

Postby Dai on Mon Oct 05, 2009 11:01 pm

the factory code is the semi-circle with the dot ("Elektronski Industija, Nis, Yugoslavia" on that page) which you can see on some of the tubes in the bottom two pics. If it looks like a circle with line, then maybe it looks that way because the print is not very "focused" looking and kind of smeared. Philips have the "delta", plus the plates are different. As for the accuracy of that chart, IME it seems right but that's only going by a limited number of examples to compare to. Probably Jeff W. would be the one to best answer that. Possibly TG or the few number of people who've studied dating and codes, etc. extensively.
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Re: Philips 12AX7 ECC83 found in amp...

Postby Axe Grinder on Sat Oct 17, 2009 10:25 am

I had a few of those flash violet / purple and pop.
I hate EI....I stay away form there power tubes as well
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Re: Philips 12AX7 ECC83 found in amp...

Postby psychodave on Mon Oct 19, 2009 2:39 am

I love those and wish I have a few more... 8)

I have one in V1 of both my Cameron Modded Marshalls. One is labeled from Grooove Tubes, the other reads "National". Both are quiet...in hot rodded amps :jam:
I have a lot of stuff!
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Re: Philips 12AX7 ECC83 found in amp...

Postby Sterling on Tue Oct 20, 2009 8:59 am

Older Ei are a great tube. Probably is the European ECC83 with more American concept. Solid and stout sound, very lineal with little compression and little harmonic artifices.
The succession that Groove Tubes has used to support the concept "7025" across the time has been:
American 7025 > ECC83 Tungsram > ECC83 Ei (a relation exists between them)
ECC83 Ei was the last great European ECC83
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