Very Simple Hybrid Ampifier

[vzaichenko]

Bump.
I have prepared another board (to be fitted flat with the heatsink), I did some minor changes + added emiter fallower just after VAS. Looks that there is some improvement made. The IMD products are gone, there is only 50/100Hz hum visible from my crap wiring setup
I have some meas on my table with wires ect. but for now it looks like bellow.
No problems with bass either, very dynamic clear sound.

I have tryed to drive 2 pairs of LATfets dirrectly from 4,5mA VAS and didnt spotted any issues, squares were very clean without any signs of problems. Those transistors maybe are not the stronges ''horses'' but to drive them is very easy.

I think I must get some more voltage on the rails and try some 2 pairs as a next step.

Valery

To balance the mosfets capactance (RC's) I have used the 470R/330R. Would be correct way or maybe better use the same resistor values at the gates and put some small cap instead (like in Yours TuboSumo amp ??).

THX


BTW
I am listening the Dayton RS125 based monitors and must say this is my first Dayton and it is really awesome speaker !!

Hi Peter,

It's a cool compact hybrid!
As for me, 220pF caps between the gate and the drain of N-channel FETs worked most reliably. However, if it doesn't show any problems with the different gate stopper values - leave it, it's also a viable way of aligning the time constants.

Cheers,
Valery

 

[borys]

I have stuffed enclosure with all pcb's psu's etc, so my hybrid is up and running, but it needs a small update, I will have to add a V bias generator to compensate drivers Vbe, becouse I do not like to wait for bias to climb up.
Other than that amp is playing nice enough to bring it back home from the workshop.

 

[vzaichenko]

Peter, great job - looks fantastic!

 

[borys]

Thanks Valery.

After I will finish to dig inside the amp I will paint plexi top cover for fancyier look.
Now I will have to finish some CFP crazy boards.

Regards

 

[borys]

thimios

And I did tryed the hybrid with the BJT OPS (poor man's slevmaster).
I decided also to make a few changes to make it more classic. So I have removed Hitachi VAS and putted CCS with single transistor VAS instead. I have some work left to do with it but it looks really OK.
I just can not find out why I have so much H2 at the bottom end. Sound is really good for me. The story with latfets in my case is finished anyway.
BJT's are the kings now

 

[thimios]

thimios

And I did tryed the hybrid with the BJT OPS (poor man's slevmaster).
I decided also to make a few changes to make it more classic. So I have removed Hitachi VAS and putted CCS with single transistor VAS instead. I have some work left to do with it but it looks really OK.
I just can not find out why I have so much H2 at the bottom end. Sound is really good for me. The story with latfets in my case is finished anyway.
BJT's are the kings now

Looking forward for your final version, then i will try built this one
BTW nice enclosure!

 

[borys]

That enclosure never failed me down
No fire and all staff is alive .
Soon I will make a 12au7 tube version.

 

[boyet0173]

Hi Borys, very nice project congrats

I have vssa with shaan peeceebee, can you share your listening impression compare to vssa version? Your input is highly appreciated.

I will try to build this one.

Thank you Regards

 

[borys]

boyet0173
Thanks
I do not have the vssa anymore so it would be hard to compare the amps.

I have plugged in a hybrid IPS with ecc82 and ecc83 (with small adjustment).
The ips is named VSHA Classic now because there is no any fancy super duper tricks in it.
Everyting is classic/old school/simple. Tube and six transistors soldered together.
The slev rate is around 50V/us, THD is very low and sound is really good.
The IPS is connected to the poor mans slewmaster board , it is bit over compensated for some safety reasons (unknown parameters of 12au7 tube).
Soon I will post final board.

 

[thimios]

waiting for this

 

[padamiecki]

...there is no any fancy super duper tricks in it...

very, very, very fine design!

 

[thimios]

waiting for this

 

[boyet0173]

Thank you borys for the review. We'll waiting for final implementation

 

[borys]

The PCB is ready anyway, there is only left some resistors adjustment.
I will post the boards at the weekend.

Today I was working on third IPS and suprisingly the whole top octave was more smooth/delicate in transistor IPS than tube IPS, looks like good sound have a lot of virables which are not easy to find. I had to try that super fancy VAS

Bellow Cliffjumper


Regards
Peter

 

[borys]

And few scope readings from hybrid IPS

 

[Vostro]

Hi Borys what sig gen do you use.

Regards

 

[borys]

Vostro
Unfortunatley I use DDS cheap'e from ebay, the analog one would be much better, but for my needs is ok.

Regards
Peter

 

[Cambe]

Borys, outstanding!
I also will be looking forward to building this project.

 

[borys]

Bellow some files for thermotransfer of IPS VSHA Classic, tube 12AU7.
I have some fine tuning left to do --> there would be only some minor changes.

 

[still4given]

Hi Borys,

I'm trying to get the IPS working but I have a huge offset. I'm attaching a schematic with voltages. When you get a chance can you take a look and see where it looks like its going awry?

Thanks, Terry