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Opinions on Valve Art 6550 tubes?

GordonW

GordonW

Speakerfixer
Subscriber
OK. Gotta re-tube a friend's Conrad MV-75. Stupid zener diodes in the bias supply shorted, took out the quad of Winged C outputs.

Needless to say, that's the LAST time there will be a zener diode in this amp. BrassTeacher is changing out the supply, to a standard RCRC filtered supply with a voltage divider. That'll track the main supply (what a concept!)!

But- as for new tubes- anyone got an opinion on current production Valve Art/Shuguang 6550s, especially from a QC standpoint? Looks like a decent alternative to the (sometimes unreliable in ultralinear amps) EH KT88s. Gold plated grids+ overload = shorts all over the tube due to the migrating gold... I don't think that the Shuguang/Valve Art tubes have that?

Or, should I just go back with another set of Winged C 6550Cs? :scratch2:

Thanks for any help...

Regards,
Gordon.
 
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I have noticed that RF Parts is carrying a version of this tube (the Shuguang-built Taylor 6550). Though it says absolutely nothing about audio quality (pro or con), it at least would seem to indicate that it might be built like the proverbial brick outhouse? :D

Regards,
Gordon.
 
GordonW said:
OK. Gotta re-tube a friend's Conrad MV-75. Stupid zener diodes in the bias supply shorted, took out the quad of Winged C outputs.

Needless to say, that's the LAST time there will be a zener diode in this amp. BrassTeacher is changing out the supply, to a standard RCRC filtered supply with a voltage divider. That'll track the main supply (what a concept!)!

But- as for new tubes- anyone got an opinion on current production Valve Art/Shuguang 6550s, especially from a QC standpoint? Looks like a decent alternative to the (sometimes unreliable in ultralinear amps) EH KT88s. Gold plated grids+ overload = shorts all over the tube due to the migrating gold... I don't think that the Shuguang/Valve Art tubes have that?

Or, should I just go back with another set of Winged C 6550Cs? :scratch2:

Thanks for any help...

Regards,
Gordon.
Click to expand...



I would stick with the Winged C. The Penta KT88SC is very nice, and a step up in sonics, but will run about 10.00 per tube more.
 
GordonW said:
I have noticed that RF Parts is carrying a version of this tube (the Shuguang-built Taylor 6550). Though it says absolutely nothing about audio quality (pro or con), it at least would seem to indicate that it might be built like the proverbial brick outhouse? :D

Regards,
Gordon.
Click to expand...

RF parts isn't setting any light bulbs off in the brain.... who are you talking about?

Craig
 
Craig, that was what I was thinking, re: the price. And if it's specified for RF... one would think that reliability problems would be "screened out"? Kind of hard to get those transmitter guys to use anything that isn't pretty reliable. It's one thing when your home audio system goes on the fritz... quite another when your radio station won't stay on the air...

And, as low of a distortion spec as the 6550 has... it's hard to imagine one that would sound THAT bad. Funny thing, the RF guys have even more stringent linearity requirements than do any of the hi-fi or TV guys... they HAVE to have a nice low IM distortion in the amps... otherwise, they're "stomping" all over adjacent transmission channels!

Regards,
Gordon.
 
I would think the reissue gold lion KT88's would have to be one of the best selections of currently produced tubes for the mv75.... That is probably what will eventually end up in my project mv75a.

Short term I am going to use EI KT90's that I already own, which I have compared directly to a very good pair of original genelex KT88's, and I really can not say the genelex's had anything on the KT90's sonically (both being FANTASTIC), with the KT90 being a more robust tube, having 50 watts of plate dissipation and can handle up to 750vdc on the plates. Biggest problem with the EI KT90's is finding any you can afford, with recent quads seen going in the $400-$450 range. Plus, many of the EI KT90's did vary a bunch in bias and gain, and is difficult to come up with a well matched quad. They went out of production in about 2006. Have not heard that much positive regarding the EH KT90's.
 
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GordonW said:
Craig, that was what I was thinking, re: the price. And if it's specified for RF... one would think that reliability problems would be "screened out"? Kind of hard to get those transmitter guys to use anything that isn't pretty reliable. It's one thing when your home audio system goes on the fritz... quite another when your radio station won't stay on the air...

And, as low of a distortion spec as the 6550 has... it's hard to imagine one that would sound THAT bad. Funny thing, the RF guys have even more stringent linearity requirements than do any of the hi-fi or TV guys... they HAVE to have a nice low IM distortion in the amps... otherwise, they're "stomping" all over adjacent transmission channels!

Regards,
Gordon.
Click to expand...

Gordan,

When it comes to output tubes like KT-88's that are usually operated at pretty high B+ and current I've yet to find a bullet proof solution it's kind of a luck of the draw type thing. I see zero advantage to over priced tubes like the reissue Genelax and other higher priced offerings... When it comes to Sonics I prefer just about any Shugaung made KT-88 with the Penta Labs KT-88SC being my favorite... But the price of those jumped up big time this last go around ($180 a quad). I prefer this tube by a large margin over anything made in Russia both Sonically and longevity wise. I logged about 8000 hours of hard use on a set once and finally dropped one when tube rolling and broke it...ouch! The things just wouldn't die I still have the other 3. BUT AGAIN I THINK THIS WAS LUCK OF THE DRAW. I've been running a quad of Valve Art KT-100's from AES for about 3 years now...they must have 6000 or more hours on them now. They show some signs of wear and tear but still bias dead stable and test strong in my tube tester.

I've supplied 100's of various brands of tubes in amplifiers I build, I allow the customer to specify brand if they like I figure no sense fighting the hype ;). I have yet to see a brand that does not have early failures for no apparent reason including the tubes mentioned above. So in the end my personal choice is what sounds the best out of the mid level priced offerings and this hands down is Shugaung made KT-88's.

I'll be curious to see your results with the 6550's.
 
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hate to disagree, but keep in mind the mv75 has about 600 volts on the screens, most cheap chinese tubes will not be happy campers......
 
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