K&K Audio / Lundahl Transformers

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Sakuma amp

171.101.39.161
Posted on March 25, 2015 at 07:44:01
JK-Tri amps
Audiophile

Posts: 3
Location: Mid west
Joined: March 25, 2015



Is it possible to use KT150 run in pentode for Sakuma schematic base. And use Lundrel transformer & choke.

 

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RE: Sakuma amp, posted on March 25, 2015 at 18:49:16
KevinC
Manufacturer

Posts: 2984
Location: NC
Joined: April 19, 2001
 If you mean use the KT150 in pentode mode for all three tubes, no it's not really feasible. There are two problems. First using the KT-150 as a pentode changes the plate impedance drastically, so that the interstage transformer selection is very narrow. Second, without negative feedback in the output stage, the output impedance will be high and will not interface well with speakers, especially in the lower midrange / upper bass region where most speakers have a low impedance dip.

Kevin Carter
K&K Audio
www.kandkaudio.com

 

RE: Sakuma amp, posted on March 25, 2015 at 21:34:55
JK-Tri amps
Audiophile

Posts: 3
Location: Mid west
Joined: March 25, 2015



I like the concept of Sakuma that he use a 845 as amplify tube and (2) 845 as out put tube as well. Perhaps is it possible to do Tri-amps or bi-amps on KT150 and adjust any necessary transformer & choke value according to frequency needed...woofer, mid, high. I am a beginner in DIY audio, John Lumley has been guiding and helping me all along. I do have a pair of good ears. And very adventure of doing something difference. I have been experimenting doing Tri amps and work fairly well (see attach pict)
Bass amp: Krell KSA 50 driving JBL 18" & Altec 15"/side
Mid amp: Stromburg heavyly mod by John Lumley & my self drive 3-Altect horn/side
High amp: Quad II driving 6-Fostex super high freq/side
All dual mono amp, and dual mono pre amp 3/side (see pict)
Now would like to try something new in amplifier gear and Sakuma schematic caught my attention. And with you & John Lumley expertise hope that can make thing happend.

 

RE: Sakuma amp, posted on March 26, 2015 at 19:52:31
JoshK
Audiophile

Posts: 820
Location: NJ/NYC
Joined: August 3, 2001
 If its your first time and given your triamp system with hi-sensitivity midrange/top, I'd go for a sakuma type amp with 2a3 all around, or you could copy the Magnequest SETH amp (sorry Kevin for the side suggestion) if you want a proven design. 845 tubes are for serious proven pros. I've built a handful of amps with up to 700v PSUs. 845s can wait.
----------------
"When Khruschev said "we will bury you" I don't think he meant with surplus parts." zacster

 

RE: Sakuma amp, posted on March 28, 2015 at 04:31:42
drdesmo
Audiophile

Posts: 32
Joined: March 10, 2003
 "the answer is blowing in the wind" Robert Zimmerman

1:4 step-up input transformer
KT150 triode connection driver
1:2 inter-stage transformer
KT150 push-pull ultra-linear output transformer

K.Carter can provide LL choices...

rgds, JNL

 

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