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Old 19th September 2014, 09:53 PM   #1
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Default SIT Power Follower revisited

Attached pics. are of the latest incarnation of my 2SK82 power follower design. I have come to the conclusion that the design benefits from a higher B+ and corresponding higher dissipation - approx. 100w per channel. Rather than stick everything in a 5U case I decided to design a more compact fan-cooled chassis. The 12v computer power supply fan is powered from an external wall-wart supply, relay switched from the amp.
Because of my chosen configuration I had to use a cased transformer to direct the airstream to either side where it comes into contact with the SITs. Part of the flow then exits via 'bleed' holes in the heatsink and the rest of the airflow hugs the inside of the heatsink to exit via the slots at the top.
As far as I can measure I have been able to achieve 0.2deg.C/W and the heatsinks are comfortably warm dissipating the combined 200w. The 1/4 inch front and 1/8 inch thick rear faceplates also contribute to the heat dissipation surface area.
I am now a convert to fan-cooling and its benefits in allowing the design of more compact enclosures when there is a need to dissipate serious amounts of class A heat.
Attached Images
File Type: jpg DSC03334.JPG (673.1 KB, 610 views)
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File Type: jpg DSC03351.JPG (679.1 KB, 214 views)
File Type: jpg DSC03341.JPG (660.7 KB, 263 views)
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Old 19th September 2014, 10:31 PM   #2
Zen Mod is offline Zen Mod  Serbia
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me likee

great workmanship

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Old 19th September 2014, 10:40 PM   #3
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Interesting 2SK82 amplifier congratulations
I like a lot big filtering caps , nice build amp !
What is output class A power ?
Schematics be always welcome.
All is perfect is a ready finished version?
What about vfet sound subjective descryption ?
Have a nice day
Best regards
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Old 20th September 2014, 04:25 AM   #4
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Really nice...

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Old 20th September 2014, 07:33 AM   #5
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100W on a 95W max device ?! i probably missed something
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Old 20th September 2014, 09:44 AM   #6
Zen Mod is offline Zen Mod  Serbia
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ya see these golden resistors ?

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Old 20th September 2014, 01:07 PM   #7
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Quote:
Originally Posted by Zen Mod View Post
ya see these golden resistors ?

probably heat fuse
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Old 20th September 2014, 02:20 PM   #8
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I really hope not, but I strongly suspect that a large part of my motivation in posting is a shameless angling for approbation from the more exalted members of this forum - thank you Zen Mod and Mr. Pass .
Soundhappy - Refer to the thread ' SIT Variations ' for the original schematic. The current design is just a higher voltage version with corresponding higher dissipation. The theoretical output of the design is about 10 watts but realistically, usable output is 5 to 7 watts and that is going downhill with a strong tailwind !
As to sound quality - Few of my DIY attempts make it pass the bread-board stage. Fewer still possess sonic qualities meriting further refinement. That this source follower design is in its 'mark 2' version says something of my regard for its sonic qualities. I am however, not ready to give up on tubes and I am just about to embark on building what I consider to be the ultimate expression of single-ended amplifier design and that is tube based.
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Old 20th September 2014, 09:12 PM   #9
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Quote:
Originally Posted by audiong View Post
Soundhappy - Refer to the thread ' SIT Variations ' for the original schematic. The current design is just a higher voltage version with corresponding higher dissipation. The theoretical output of the design is about 10 watts
Yes i find it !
SIT Variations
Thanks for your answer
Greetings
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Old 21st September 2014, 06:14 AM   #10
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Nice, they make some nice enclosures from our sponsors, we make heat sinks at work, any kind you can imagine
we need the work, BTW nice unit, a labor of love...
Rob
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