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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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 .
 
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2 picoDumbs

Member
2013-09-06 9:35 am
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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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 .
 
kess52

Thanks for your input and for your efforts ! ,

I`m sure that we need the real good J-Fets models for exact sim results ,
any way it is my opinion that power J-Fets(SJEP.....) is not so hard device for driving , special not via step down driver transformer ,
btw , for your information check this EV service manual where SEPP- AB class biased BJTbased OPS is driven in similar manner via small driver transformer ,
that vintage SS amp sounds pretty decent even for today standards .
ps , your sim and schematic look very interesting ! :up:
 

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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 .

I get this when sim it for you, better then the single supplty version.

hamronic content is higher, can sound nice, feedback is current version.

did put the circlotron also, as a test, do need work afcouse, exper.

regards
 

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Kess52

Again many thanks for your support and your efforts !

just few remarks ,

- Bipolar supply voltage for SEPP-OPS is way to high! ,(+/-57VDC),
I was think to use max +/-28,5VDC for that purpose since I already have some very powerful main transformers for this amps ,

-I think that you use 12AU7 model since you don`t have 6C45P sim model ,but 12AU7 tube is too weak for driver purpose , 6c45P triode is the right tube for that position or eventually Siemens pentode typ D3A but triode strapped ,

- Triode driven Circlotron A class OPS is already done by few our members from this site , you can see that project here Amplifier End by Andrea Ciuffoli

,but the main reason why I insist on the SEPP A class OPS and not on the Circlotron OPS is different output harmonics contents with 2`nd one harmonic as dominant , expecting that this type of amps will be sounding very close to sound of some typical SET tube amp.

-edit , one very good option for driver transformer is Lundahl typ LL1671
 
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BTW ,

same amp concept but now with different sort of SS power devices (which I don`t have yet :))

Sanken ring emmitors are extreme liniair, but do not now if she still be made, is used in expensve high end amps.

Why you do the idle system not from a center tappen transformer? because I did try use zemers fopr stabilization and it do not work wel on negative side, the sepp/ots itselfs with one supply do work.

regards