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Old 1st July 2003, 02:12 PM   #1
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Default power amp using kt88

dear all,
can anyone provide some schemetic of good and easy build class A power amplifier using KT88?
since i want to start a new power amp project~

thanks
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Old 1st July 2003, 07:33 PM   #3
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I've designed one myself, however I can't give any guarantees that it will work the way you wan't. I have successfully assembled one channel to try out and it works like a charm, the only "problem" is the low output power. But I'm beginnig to think that low power is something that almost all single-ended amps are limited by. Anyway... here is the schematics

http://213.67.45.70/se_kt88_3.gif

[edit]

About the cathode-resistor for the KT88. I've tried 470 and 330 ohm. Both with good result. It feels like it sounds best with 470, which makes the amp draw 75mA at 400V.
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Old 1st July 2003, 07:39 PM   #4
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You might also wanna check this page

http://www.bonavolta.ch/hobby/en/audio/kt88.htm
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Old 1st July 2003, 08:02 PM   #5
SY is offline SY  United States
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If you're not restricting yourself to half-@$$ed amps (single ended), I'd build the classic Williamson circuit. Well proven. Use a 380V B+, 4000 ohm p-p, cathode current at about 80-100 ma per tube. You'll get about 25-30 watts in pentode, put out a satisfyingly large amount of heat, and help your tube dealer make the next payment on his Mercedes.
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Old 1st July 2003, 10:34 PM   #6
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Hi,

Quote:
You'll get about 25-30 watts in pentode, put out a satisfyingly large amount of heat, and help your tube dealer make the next payment on his Mercedes.
He,he...how do you think I managed to run five Porsches in those days?

Anyway you look at it once you decide for class A, "la classe royale" as we call it, you have to bear the cost.

I love what it can do but to me it's not a must unless you go the SE path....upon which I'd rather not comment.

Cheers,
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Old 2nd July 2003, 12:15 AM   #7
SY is offline SY  United States
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Quote:
"la classe royale" as we call it
Because it will cost you a fortune in tubes and electric bills?
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Old 2nd July 2003, 12:30 AM   #8
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Hi,

Quote:
Because it will cost you a fortune in tubes and electric bills?
Make that a kings' ransom nowadays...glad to see you keep your sense of humour, SY.

Still, it is called that way over here for it's in the eyes of many people the only valid road to sonic bliss.

All in all I tend to agree although I do not always obey, running even less efficient OTL amps myself.

Now if I were to be running vintage AD1s or PX somethings into class A on a daily basis I'd make sure I'd play the stock market right.

Cheers,
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Old 2nd July 2003, 12:41 AM   #9
SY is offline SY  United States
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My Class-B amps bliss me out, or they would if I could only get my kid to grow up fast enough not to electrocute himself so I can actually use them again. Three more years in the garage, I figure. For the amps, not the kid. My wife unaccountably gives Jimi run of the house.
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Old 3rd July 2003, 03:29 PM   #10
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thanks a lot, i am planning to do this

http://www.bonavolta.ch/hobby/en/audio/kt88_1.htm

any comment?
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