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Old 17th January 2004, 04:14 PM   #21
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Wow this rocks my understanding of Russian manufacturing!


I'm sorry thread maker for saying "I'm buying Svetlana"

I aint now!
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Old 17th January 2004, 04:14 PM   #22
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Layberinthius,

Yes, both Svetlana 6550C tubes failed and caused damage to my power amplifier. As I recall, the screen grid resistors cooked (but I may be in error).

The Sovtek KT88 tubes produce a very natural sound in my opinion.
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Old 17th January 2004, 04:16 PM   #23
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ahh resistors...

Mmm very perplexing..

They must be getting desperate with manufacturing?

Gold plating and all to stop grid current...
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Old 17th January 2004, 04:20 PM   #24
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fdegrove,

What do you know about the EH KT88 tube?

As I have posted, I can't say enough good things about the EH 7591A tube (as it performs in my old HH Scott 299C amplifier).

Another Frank
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Old 17th January 2004, 04:28 PM   #25
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Hi,

Quote:
What do you know about the EH KT88 tube?
To the best of my knowledge they come from the same factory most of the Sovtek tubes come from, namely Reflektor.

Like New Sensor, the major U.S. Sovtek distributor EH mostly targets the guitar amp market.

Whether there's any technical difference between either KT88, I wouldn't know but I expect not.

Cheers,
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Old 17th January 2004, 04:57 PM   #26
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Yes, both Svetlana 6550C tubes failed and caused damage to my power amplifier. As I recall, the screen grid resistors cooked (but I may be in error).

Although it makes me curl up and die to wonder what made the resistors die in the first place, I'm more interested in your theory as to why they did?

Was it a tube defect? getting too close to the plate or wha?
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Old 17th January 2004, 04:58 PM   #27
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Err disreguard that...I'm now awake enough to see my question was never needed!
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Old 17th January 2004, 08:32 PM   #28
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Hi,

Quote:
As I recall, the screen grid resistors cooked (but I may be in error).
More likely the cathode resistors.

Cheers,
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Old 17th January 2004, 08:49 PM   #29
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Someone's waking me up again with those Shugangs...... memories of Gold Lion 88's......please don't.....<Bull in a China shop> part 2??

Frank Berry.......
The bias comment on 6550 Svets you mentioned......; Quote < these two required more bias voltage than the other tubes> ....my question >.. did you come across this by measuring three tubes i.e cross section of typical manufacturing variations ??>

The selection of two out of any three should halve the worst manufacturing variations.

This bit might interest you and others...I had one new 6550B Svet which I returned because of thermal runaway (new coined)....i.e set bias for 55mA anode current and within 5mins the darned thing is up to 100mA and a glowing.....no amount of neg volts could stop it. Replace with a KT88, and no problems..It doesn't take an expert to agree that the Svet 6550 isn't really a workhorse substitute for an KT88; although it's mentioned everywhere, that-it-is....Caveat Emptor.
(Generally when using 6550 ABC's one must derate UL push-pull designs to less 470V B+ instead of 550V B+ for KT88's.... Many DIYers aren't aware of this....the 6550 tube spec was designed for mass production at lowest cost. I would never dare run any 6550 version in AB1 above 470V B+.

If there are really problems with Svetlana 6550 series, then lets hav'em out....

Appropo damage to amps: Now I always put a fast fuse in the C/T output tranny.......I learnt this lesson.. yes...from a pair of Shugang 88's which shorted internally.

rich
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Old 17th January 2004, 08:50 PM   #30
Andy G is offline Andy G  Australia
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Default to Layberinthius

just in case you are interested, WES components sell matched pairs of the Sovtec 6550WE, I have wholesale status with them.

Currently awaiting price confirmation, but I looks like around $70 (aud) a pair.

http://www.wagner.net.au/Catalogue/01_23.pdf
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