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Old 9th February 2006, 07:34 PM   #1
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Default Russian 6L6 family sketchy?

Background: I am looking to buy output tubes for an upcoming SET project. OPT's are 7.6K impedance, and B+ possibly 475V (if you this is a bad operating point feel free to interject). I am thinking Russian KT66 would be a good choice.

So I am a bit warier of the cheap Russian tubes now that I ordered some Sovtek 6SN7 and they came with the old labelling of 6H8C right on them as well as the new 6SN7 labelling. Wish I'd known that beforehand.

And so I was looking through the 6L6 family to see what was cheap on eBay, and 6P3S-E, the bigger version of the 6P3S, and I've read is often relabelled 5881, looked good. However the only datasheet for the -E version I could find listed the max anode voltage as 250V, hardly a good situation if you sub it into a 5881 amp with a higher B+.

So my question is twofold: in shopping for a Russian 6L6 family tube are there some particularly bad eggs to avoid, and are the Russian KT66's some other tube just relabelled that I could buy cheaper as a Russian equivalent?
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Old 9th February 2006, 07:39 PM   #2
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Are you dead-set on Russian? There are good, inexpensive US alternatives available.
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Old 9th February 2006, 07:42 PM   #3
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Quote:
Originally posted by SY
Are you dead-set on Russian? There are good, inexpensive US alternatives available.
No, I didn't know that there were. Do tell
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Old 9th February 2006, 07:52 PM   #4
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Check out the "super" 6BG6 at SND Tube sales. They're like $7 each and are apparently rebased 7027A. I've used them in a couple of amps here and keep ordering more.
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Old 9th February 2006, 10:57 PM   #5
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Leadbelly,

Yes, I found the Russians can be pretty free with their designations. I have listed the 6L6 variations elsewhere, I think on the "Quad" thread but cannot find it now. Summarising, there was a 6L6GB at 19W, the 5881 at 23W and the (preferred) 6L6GC at 30W plate dissipation. The Russians sometimes call everything 6L6GC. They also market a KT66 with actual 6L6 innards, but that is not such a problem as they are very close. (But do beware of Chinese "equivalents"! A no-go.)

SY,

That is good news for me - as a moderator you would have noticed my quieries from time to time about NOS 6L6GCs, which have become quite expensive. Not to doubt your word, but the only 6BG6(GA) that I find in my RCA Manual is a discontinued type with the anode going to a top cap and different base connections to 7027. Are you saying that this super 6BG6 is exactly like a 7027, or with the 6BG6 base connections and cap? You did say "rebased". Does the innards look like a 6L6? I am in the market for 10 or so, which in our economy is quite a bit of money; I cannot afford a mistake.

Regards and thanks.
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Old 9th February 2006, 11:05 PM   #6
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Both visually and in how they run in my amp, these appear to be rebased 7027A, i.e., 7027 guts with a top cap and 6BG6 pinout. The original 6BG6 spec is 20W plate dissipation- I run the "super" 6BG6 near 30 without any signs of redness. Power output is identical to EL37s that previously graced this amp (a rebuilt Eico HF87).

If I were better at photography and had a decent camera, I'd show you the tube side by side with an authentic 7027A. But since I'm not and I don't, I can only say that after buying the first 4 and trying them out, I immediately ordered 24 more.

http://www.vacuumtubes.com/6BG6.html


Disclaimer: no financial involvement there except as a very satisfied customer
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Old 9th February 2006, 11:57 PM   #7
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Quote:
Originally posted by SY
But since I'm not and I don't, I can only say that after buying the first 4 and trying them out, I immediately ordered 24 more.
I must admit these do sound great. How is the sample variation? Should I be buying the matched sets?
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Old 10th February 2006, 12:01 AM   #8
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At this price, I bought a pile of unmatched and made matched quads out of them (matched at idle current only- I didn't further do a transconductance match). The variation was unexceptional, i.e., not trivial but not extraordinary.

But SND doesn't charge a lot for the matching, so if you don't anticipate blowing through a lot of them, pay the couple bucks extra. They're still dirt cheap.
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Old 10th February 2006, 06:38 AM   #9
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There are real new production KT66.

http://www.thetubestore.com/6l65881types.html

Scroll down and the last one is exactly what you do not want (A 6L6 relabelled as a KT66). There was also someone selling Chinese coke bottle 6L6 as KT66 a couple months ago.

The Saratov KT66 and Shuguang KT66 are real KT66. I got a quad of the Saratov version on ebay 1 year ago for about 40$. I can't compare them to the real GEC KT66 (too expensive), but I like mine.

I think I read that the Groove Tube version is the Saratov one.

They are available at many places, but just be sure to get a real KT66 (the internal construction is unmistakable).
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Old 22nd March 2006, 02:00 AM   #10
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Default OK, SY, they're here!

The 6BG6's have arrived. They look so cool I am excited!

Well SY, you seem to be the expert on these, what kind of drive do they like (both SE and PP, I bought enough for both)? Will a simple grounded stage do or is something beefier required? I've got tubes like 6922, 6N1P, 6H8C, 6EJ7, 6N6P saved up, as well as some of the Group Buy Aikido boards.
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