• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

power amp using kt88

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#3
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.
 
#5
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.
 
#6
Hi,

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.
Click to expand...

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,😉
 
#8
Hi,

Because it will cost you a fortune in tubes and electric bills?
Click to expand...

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,😉
 
#9
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.
 
#11
Great choice!

I like single-ended amps with a KT88 as driver. (allthough I haven't really tried anything else) I noticed some negative vibes when I mentioned SE-designs but never mind that. They're easy to build and sound great. The only problem is the output-power, but as long as you have fairly sensitive speakers that shouldn't cause any problems. :cheerful:
 
#13
Takashi i think you have made a good choice !

I have been working around one about three years . I use

TFK brand 12ax7 , and original GEC kt88 . In the signal path

lately im very impressed with the accuracy and tonal neutrality

of the Auricaps . In the power supply for smoothing i use 6x

50uf = 300uf with ASC metallized polyprops in oil , sold by Angela

after beeing two years using old oil caps that i take off from

an american war air force RADAR of the fifties . Tantalum resistors

are very good too .

Believe me this amp , well built, can shake your furniture with only

10W . It s y life`s amp , i have another pair of GEC kt88 .
 
#15
Thats right , Joel ! I am using a large box with early nineties

KEF B200 woofer, no crossover , a Motorola ksn 1025 piezzo ,

solid silver cables , everything DIY .

Maybe at midband things merge a bit , i haven t measured , am

not sure . But i know it sounds good to me . I have been

listening rich men hi-fi for years at stores , i m not ashamed .

Jean Hiraga ! SALUT !

Regards
 
#19
Hello,

I am interested in building a KT88 single ended, and I want to use a schematic that some of you have already tried:

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

That schematic was published at the L'Audiophile magazine in 1980. ¿Do you have more details about it, or do you know where to find that article?

¿Have someone tried the second schematic?:

http://www.bonavolta.ch/hobby/en/audio/kt88_2.htm

This one was published at the book "Build your own Audio Valve Amplifiers" by Rainer zur Linde. I have already ordered that book from amazon, so I will also study this second option when I receive the book. :scratch:

About the output transformer, ¿do you think the Hammond 1627SE is a good option? hammond

¿What Sowter model is the appropiate one?

Thank you 🙂
 
#20
one more choice😀
 

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