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In Reply to: RE: 300B svetlana posted by gillougillou on November 01, 2014 at 02:02:17
There were Russian 300B's from that era that suffered from filaments that weren't properly supported. If you can get a really clear top shot of those tubes, compare them against the new EH to ensure that they have adequate support.
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Have Fun and Enjoy the Music
"Still Working the Problem"
Yeah, that's the construction you don't really want...
I have some old Chinese 300bc that use the coil springs but they still break/short out the filaments.
I've lost 3 of them but I bought 20 for about $300 and they don't sound bad.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
What a pity because I love the sound, not so far WE I think.
Is there a way to use them with less failure ?
I ran 2 of them for a long time. No problems.
I still have 15 new in the box.
I do expect a high failure rate but maybe I'll get lucky.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Nice !Are they with the "S" or the "C" (I saw the two logos on the St Pétersbourg tubes).
What year ?Gilles
Edits: 11/05/14
No, these are Chinese 300bc tubes. The predecessor to the Shuguang 300B-98.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I guess the problem is related to all Russian 300B.
A friend had a pair of 300B fail with broken filaments after some use in a 300B amp made by some local tube amp guru (most are Munchausens).
I always suspected the issue was caused by high in-rush current, and when after some time I did get a chance to check that issue, I was surprised to find that the supply was voltage regulated with 7805s limited at 1.5A: skipping on the sonic merits or faults of such solution, I have to admit that voltage and current were correct and very unlikely to be the cause of the problem.
The tubes were marked with the Reflektor factory logo.
He later acquired a pair of Sovtek 300B, and I was actually surprised to find that the basic construction of those 300Bs is identical (plate shape, filament suspension, etc) to a pair of EH300B I sometimes use (to the point that besides the base type and color they seem identical), and of course share at least the same suspension with the old Reflektor pair.
It seems to me that similarly to Chinese 300B tubes which under several brands and flavors come from the Shuguang factory, Russian origin 300B tubes are either made in the Reflektor factory, or with tools eventually taken from that factory.
As for the cause of the filaments breakage, it's probably materials quality, not necessarily the technical solution used for the suspension. The unpredictable lifetime comes from different production batches and poor purchasing standardization.
******
http://rh-amps.blogspot.com/
I haven't had any failures with the EH300B.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Neither have I, but that is not any type of guarantee.
In my view, all Russian 300B tubes seem to come from the same factory. Thus quality-wize, it might vary with the batch (sourced materials and workers skill).
Furthermore, we would need to know about the experience of normal audiophiles, i.e. people who have a pair of 300B in their (known) amp, and just liste to them for some period of time (i.e. "had them for over a year", "used those tubes more than 1000 hours", etc.).
With all frankness, I rarely listen to the same pair of output tubes longer than a week or two... not to mention to the same amp... wich obviously does not make me a good source for longevity related information.
******
http://rh-amps.blogspot.com/
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