Slewmaster - CFA vs. VFA "Rumble"

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#4,344
The "Moskido" becomes the "Torch"....

Killer !!!

I took the skido... (below 1) ,

Added a Vbe (below 2 - full schema) ..

And got the "spook" running on my "torch" OP stage.

The single Vbe will stabilize the IRFP's (mosfets).

I've yet to refine the idle adjustment for the class A ...
either the OP's CCS's will adjust this (or the Vbe).

performance is awesome .. 5ppm thd20 and
just low order harmonics in the FFT (below 3).

PS - the heck with the link ... Pass said it looked interesting , 4 more
posts ... no one ever built it. Things will happen here.

OS
 

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#4,347
Groner/GK's stage can be very linear, fast (1KV/uS) and "simple" when it is preceded by an LTP or emitter-feedback input stage like in Groner's article.

GK actually uses it much differently than Groner does. GK uses it more traditionally, but Groner takes advantage of it's nuances very well.
 
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#4,349
ostripper said:
Killer !!!

I took the skido... (below 1) ,

Added a Vbe (below 2 - full schema) ..

And got the "spook" running on my "torch" OP stage.

The single Vbe will stabilize the IRFP's (mosfets).

I've yet to refine the idle adjustment for the class A ...
either the OP's CCS's will adjust this (or the Vbe).

performance is awesome .. 5ppm thd20 and
just low order harmonics in the FFT (below 3).

PS - the heck with the link ... Pass said it looked interesting , 4 more
posts ... no one ever built it. Things will happen here.

OS
Click to expand...

I experimented with it last week in simulator... as a candidate for no GNFB design.
At around 0.5A per pair (and above) - very good performance, but - a bit "nervous" with square wave response and an interesting artifact on frequency/phase response at around 200 MHz - I'm sure those things are inter-related.
With GNFB loop and proper compensation in place this "ringing" goes away, but I want to try killing it "locally" first 😉
 

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#4,350
vzaichenko said:
I experimented with it last week in simulator... as a candidate for no GNFB design.
At around 0.5A per pair (and above) - very good performance, but - a bit "nervous" with square wave response and an interesting artifact on frequency/phase response at around 200 MHz - I'm sure those things are inter-related.
With GNFB loop and proper compensation in place this "ringing" goes away, but I want to try killing it "locally" first 😉
Click to expand...

Source is feedback to the driver stage .

the "skido" seems to be a simpler (current FB) version of the "Genesis" class A stage (below),
which uses local voltage FB to a pair of differentials.

A lot more FB , I could never get the genesis to be really stable ???
Maybe understanding the "skido" will unlock the genesis.
When it is behaving , the genesis is the "holy grail" (super linear /0 distortion). 😕

I'll get it !!

OS
 

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#4,351
ostripper said:
That would be a easy as porting the IPS/VAS to 18-24V rails.

(below 1) is the "spook" with a few resistors changed .. running an EF2
class A OP into a 250R load.

The slewmaster IPS's can easily be ported to preamp/headphone OR
a larger power class A stage. NO mods needed (beside value changes).

If someone would give me a few ideas for a push-pull class A op?? .... 😎
Parts per billion territory for your headphones 😀 .
OS
Click to expand...

ostripper,can you post a schematic of cfa-X and spooky as 10dB preamplifiers ported to +-18Volts with the new values and the EF type 2 output stage?
 
#4,354
SleMaster with Toshiba mosfet help PLEASE

First of all I would love to know can I post a schematic here.
That is actually based on the IRFP Hex Fet version but with Toshiba Fets..
I just don't want to go on and pollute or hijack the tread.
I know the SlewMaster was used with IRF mosfet , I have some Toshiba 2SK1530 & 2SJ201 audio transistors - there are some minimal differences between the two type..
I would love to put them in good use those Thosibas.🙂
These project since to me I could be the one for those parts and with some help may be I will be able to bring out good sound quality and build a great amplifier with those mosfets , my dream would come true.

My question can I post my mosfet (Based on the IRF) circuit here or I should start a new tread.

Please let me know
Thank you very much🙂
Greetings gabor
 
#4,355
vzaichenko said:
Hi All,

Another contribution to front-ends collection. Still a little bit under construction - no prototype yet. This is a revised version of my initial hybrid. I was working on it, mostly focusing on keeping the balance during start-up, when OS inspired me by super-pair VAS. So, this is what I came up with in the end.
THD20 is not measurable by Multisim even at 40V RMS output swing, low TIM by design, nice clipping. Much better behavior at start-up, thanks to a-la-Sansui symmetric mirrored LTP approach.
This is the next one I will prototype - working on PCB...

Comments are welcome 😉

Cheers,
Valery
Click to expand...

Hi All,

I have moved this discussion to a separate thread - >HERE< 😉

Cheers,
Valery
 
#4,356
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