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Old 8th May 2016, 09:53 PM   #1
banat is offline banat  Serbia
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Default Hybrid A-class retro amp

Hi guys
for long time I want to made pair of hybrid amps based on this retro configuration ,
where simple 1W A-class SET amp will drive A-class SEPP-OPS using pair of modern Njfet power devices or several pairs of power latfet`s ,
yours suggestion and critics are welcome !
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File Type: jpg SET+SEPP.jpg (229.3 KB, 716 views)
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Old 8th May 2016, 09:57 PM   #2
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1st that comes to mind is it has a coupling transformer, so not for HiFi use. It has no balanced power supply, so prone to power supply noise.
Looks a bad idea to start with.
Sorry.
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Old 8th May 2016, 10:10 PM   #3
banat is offline banat  Serbia
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Originally Posted by JonSnell Electronic View Post
1st that comes to mind is it has a coupling transformer, so not for HiFi use. It has no balanced power supply, so prone to power supply noise.
Looks a bad idea to start with.
Sorry.
Thanks for your input !

- I will not reject quality coupling(driver) transformer per se
- it is easy to convert PSU to be with balanced supply lines , but I think good filtered unbalanced / unregulated PSU can do the job to .

Last edited by banat; 8th May 2016 at 10:13 PM.
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Old 8th May 2016, 10:17 PM   #4
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Another possibility.
Do the valve stage as a preamp with regulated supply.
Then on poweramp just do F6 topology with jfet buffer input and sjep mosfets, but with correct transformer polarity to account for inverted preamp signal.
Job done.
Should sound nice. I'd certainly build it.
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Last edited by 2 picoDumbs; 8th May 2016 at 10:20 PM.
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Old 8th May 2016, 10:33 PM   #5
banat is offline banat  Serbia
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Originally Posted by 2 picoDumbs View Post
Another possibility.
Do the valve stage as a preamp with regulated supply.
Then on poweramp just do F6 topology with jfet buffer input and sjep mosfets, but with correct transformer polarity to account for inverted preamp signal.
Job done.
Should sound nice. I'd certainly build it.
Thanks for your input !

But mine primary idea is low power but already very good sounding 1W SET amp to drive directly SEPP A-class OPS ,
where SET PSU will be based on EZ80 tube rectifier .
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Old 8th May 2016, 11:54 PM   #6
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Leave off the jfet buffer then.
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Old 9th May 2016, 12:10 AM   #7
Bigun is offline Bigun  Canada
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Some related stuff here: Lundahl Hybrid Amplifier
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Old 9th May 2016, 12:11 AM   #8
banat is offline banat  Serbia
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Originally Posted by 2 picoDumbs View Post
Leave off the jfet buffer then.
Of course , jfet buffer is not necessary here since 1W SET drive amp will work almost unloaded , special in case if headphone is disconnected .
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Old 9th May 2016, 02:11 AM   #9
banat is offline banat  Serbia
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Same hybrid concept,
but now with bipolar PSU with virtual ground point and three or more N-type latfet pairs for SEPP-OPS .
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File Type: jpg SET+SEPP+ bipolar PSU.jpg (235.5 KB, 631 views)
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Old 9th May 2016, 02:46 AM   #10
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Quote:
Originally Posted by Bigun View Post
Some related stuff here: Lundahl Hybrid Amplifier
That looks good Bigun.
I have some some ideas for that one.
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