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Old 9th September 2007, 06:09 PM   #11
EC8010 is offline EC8010  United Kingdom
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Default Ribbed anodes for extra sensation?

It's not the anode structure that causes microphony, it's those grid wires wobbling back and forth close to the cathode.
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Old 9th September 2007, 06:53 PM   #12
SY is offline SY  United States
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"For her pleasure."

Smooth-plate Telefunkens were the fashion rage back in the late '70s. I scored some and used them in my preamp at the time (a Berning TF10 prototype). Nothing special. Tried them in an SP6. No big deal.

In my preamp, the tubes which worked best were some Eastern European jobs with tiny plates (looked like an ECC81) and rather fat envelopes. When I pulled some of these specimens out of storage a couple months ago and measured distortion spectra, they were surprisingly similar. And quite good, too, I should add. The Eastern Europe tubes had a fascinating array of indicated countries of origin...
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Old 10th September 2007, 04:17 AM   #13
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Default 12AX7/ECC83

Quote:
The Eastern Europe tubes had a fascinating array of indicated countries of origin...
During the cold war, the USSR and Warsaw pact countries needed to bring in hard dollars, and one scheme was to export tubes to intermediary countries, mark them as "Made in England", "Made in West Germany", etc., then export them to the United States. The customs inspectors didn't know enough to identify them as eastern European or Soviet tubes. After trade restrictions were lifted, more legitimate companies still imported these tubes, often with the fake country of origin. I've seen Russian tubes sold as RCA and Amperex. By the way, a tip-off for a Russian tube is the use of a "flying-saucer" getter, which seems unique to Russia. They did use conventional getter types, too.

The smooth-plate Telefunkens were Telefunken's version of the long plate structure. Apparently the lack of ribs didn't affect performance, and as EC8010 pointed out, it is the movement of the grid and cathode that makes the most microphonics. The one thing I've noticed about the smooth-plate Telefunkens is their amazing longevity. While in college, I worked as a technician for the music department, and every summer, checked all the tubes in the equipment on campus. The Tele ECC83s that were in the Dynaco PAS-2 preamps we used all over campus never seemed to change, even though they were over 15 years old and being used heavily every day! At the other extreme, 7199s and 6AN8s lasted about a year or two. I've noticed the longevity of Telefunken tubes in other equipment since then.

The smooth-plate Telefunkens (at least the real ones, not the recent knock-offs) do sound really good - kind of smooth and clean. However, they are like a tone control, and if this is not what you need or want, then don't use them!

I am quite sure that the smoothness of the plates is not what makes the Telefunkens sound good, but rather materials and processing. This is why the knock-offs are not very impressive.

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Old 16th February 2008, 08:32 PM   #14
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Default Re: 12AX7/ECC83 shapes

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Originally posted by JohnAtwood
On the other side of the iron curtain, the USSR came up with a completely different design for the ECC83/12AX7 that I think originated with the 6N2P. There was a shield between the two sections, the plates were even shorter than the American/European short-plates, and the plates were spaced rather far from the grids. Again, the grid and cathode were adjusted to give the standard ECC83 characteristics. This design also showed up in China, and the bulk of newer tubes from Russia or China are of this design.
Just came across this old thread in a search on the 6N2P. What I was looking for was any support for lower Miller capacitance of Russian 6N2P versus NOS 12AX7/ECC83. The 6N2P datsheet specs Cg1a as 0.7 pF, which is better than typical NOS. Make sense in light of John's comments, or an example of a wishful Russian spec?
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Old 16th February 2008, 08:46 PM   #15
ilimzn is offline ilimzn  Croatia
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Originally posted by SY
In my preamp, the tubes which worked best were some Eastern European jobs with tiny plates (looked like an ECC81) and rather fat envelopes.
This design, I believe, originates from RFT in (then) East Germany, but was, to my knowledge, also made by Tungsram in Hungary, although their ECC83 originallu looks like a Philips. It is quite possible that later they just relabeled the RFT tubes. Also, later these were used by many rebranders on the western market, perhaps because they were very cheap to buy from the hard cash strapped eastern block countries.
I have a number of these with different labels. It also seems there was an ECC82/12AU7(A) with that kind of plate structure as well (certainly makes it difficult to determine which tube it is if the label gets rubbed off )
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Old 17th February 2008, 01:59 AM   #16
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my tube 'guru' friend who is a major 12AX7 collector (go figure) swears by the early RCA 'long' blackplates as being 'the best'. Of course he warns about microphonics being the biggest issue with these early long plate tubes. After that he is a Mullard guy through and through - but I suppose it would depend on the equipment being used. In my book the 12AX7 is best used for guitar amps and quick n' dirty phono stages (where fidelity is not highest priority on the list).

Having said that, I heard some amazing systems that used 12AX7s back in the day when I first heard tube amps/preamps. But in these cases the 12AX7 was used in in a section with an outboard regulator in use. Most vintage stuff 12AX7 circuit sounds incredibly sloppy to me now and I wonder how my ears would react to those old systems I heard back then.
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Old 17th February 2008, 08:42 AM   #17
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Quote:
What is the difference between the 'standard' ECC83 and the version with the 'long' plate ?
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