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RE: Sovtek KT88's


 
3/14/2000 7:02 PM
Psycho Bass Guy
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RE: Sovtek KT88's
Sorry I took so long on this, been mucho busy. My Trace does indeed run UL and throws the same 728 volts to both elements. The Sovteks take it and run just fine. Hope this helps all you lost KT90'ers out there.  
 
Psycho >^}
 
3/14/2000 10:59 PM
Reid Kneeland
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quote:
"Sorry I took so long on this, been mucho busy. My Trace does indeed run UL and throws the same 728 volts to both elements. The Sovteks take it and run just fine. Hope this helps all you lost KT90'ers out there."
 
 
Are you sure about that? I wrote to TE and asked for voltage info for the VR400. They sent me a service manual (in PDF form) for the VA400 which they said was very similar. This amp has 685 V on the plates, and 365 on the plates (pentode wired). 785 UL would seem to be really pushing it, given the 600 V screen rating.  
 
Reid  
 
 
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3/14/2000 11:59 PM
Psycho Bass Guy
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Trace wouldn't even SELL me the schem for the VA 400 because of the differences. It puts 728 both ways, plate and screen. It used to sit at 734 with 6550's. FWIW worth, when it had the 6550's, it dropped voltage on the grids much faster than the plate voltage. The Sovetk KT88's solved that and made it MUCH more stable. That 728 volt reading is under load and doing a near clip 400 Hz signal BTW.  
 
Psycho >^}
 
3/15/2000 1:14 AM
Reid Kneeland
email

quote:
"Trace wouldn't even SELL me the schem for the VA 400 because of the differences. "
 
 
Hmm... sounds like Trace needs to get their story straight! Thanks for the info, it means that I could use Sovteks in my amp.  
 
Reid  
 
3/15/2000 1:17 AM
Reid Kneeland
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BTW, if anyone wants the service manual for the VA400, I'll be happy to email it (all 791K).  
 
Reid  
 
3/15/2000 2:59 PM
kg
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reid, did those kt90's go tits up after all?  
 
yeah, please send me a copy of that bigass schematic. i'm always in the mood for something else to peruse while sitting on the throne ;-/  
 
ken
 
3/15/2000 10:17 PM
Reid Kneeland
email

quote:
"reid, did those kt90's go tits up after all?"
 
 
Is that what you call the top nipple? :-)  
 
They seem to have survived, although the power output is down about 10%. They sound good, though. One weird thing is that although they're now much closer together in their idle currents, the crossover distortion that I see on the scope is less symmetrical (the so-called notch is noticeably lower on one side of the wave than the other).  
 
I'll send along the service manual. Interesting amp, it's got a solid-state pre and tube output - kind of a Music Man on steroids.  
 
Reid
 
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