Topology Federmann, HQQF-55 ...

[Upupa Epops]

SOAR IRFP240/9240 by 90V : circa 3,5A/10 msec. By simulation : 30A/5 = 6A....

[Federmann]

You're right, it's just a demonstration.

When supply voltage is 91V output power:
1) 500W/8Ω. Zener diode must be selected so as to limit current to 12A (2.5 A * 5 or 3A * 4).
2) 1kW/4Ω. Zener diode must be selected as a transistor must be 8 or 10 pairs of 25A (2.5 A * 10 or 3A * 8).

[Upupa Epops]

Federmann, in opposite to you, I had build in last twenty years several hundred mosfet amps and I had in my hands several thousand mosfets...I have practical experiences, not only these f... simulations like you...Show to us practical results, not only these theoretical blables

[PMA]

Originally Posted by Federmann

Zener diode must be selected so as ...

I wonder if it is possible to make it so and to keep both linearity and protection. I am saying IT IS NOT.

Federmann, you argue here with people like Pavel Dudek (Upupa Epops) who has designed a lot of professional amplifiers that were sold in thousands, and with Ladislav Bunta (BV) who makes a living like an amplifier designer and producer, and again is commercially succesfull.

Contrary to that, you display some strange ideas, that are potentially hazardeous and dangerous for potential less experienced builders. You have no prototype, no sample. I must mention that, though I get a risk to be treated somehow. I hope there are some competent people who MUST see that.

[brianco]

Originally Posted by PMA

I wonder if it is possible to make it so and to keep both linearity and protection. I am saying IT IS NOT.

Federmann, you argue here with people like Pavel Dudek (Upupa Epops) who has designed a lot of professional amplifiers that were sold in thousands, and with Ladislav Bunta (BV) who makes a living like an amplifier designer and producer, and again is commercially succesfull.

Contrary to that, you display some strange ideas, that are potentially hazardeous and dangerous for potential less experienced builders. You have no prototype, no sample. I must mentione that, though I get a risk to be treated somehow. I hope there are some competent people who MUST see that.

It seems that the big danger is the technically not-competent person who does not see whatever danger may exist.

[PMA]

Originally Posted by brianco

It seems that the big danger is the technically not-competent person who does not see whatever danger may exist.

Exactly, you got it right.

[stinius]

Originally Posted by PMA

I wonder if it is possible to make it so and to keep both linearity and protection. I am saying IT IS NOT.

I agree; it is NOT possible.

[BV]

Overcurrent "protection" is one mistake, showed frequency compensation second.. It will be for sure power oscilator (for short time before explosion), slow output stage and "fast" input and VAS without local compensation closed in global NFB..Unrealistic. We have to wait for measured results.

[PMA]

To explain a bit. 5 years ago I posted a thread
New error correction amp
This thread described MOSFET output stage with error correction. The output devices were Hitachi 2SK413/2SJ118, similar to IRF range of devices rather than to laterals. The circuit operated pretty good, with one exception - the error correction acted as current limitation as well. It did not enable dVgs of both output MOSFETs above some level. It was fine, until the dVgs limit was reached - then horrible current limitation appeared, with terrible sound effect.

There is a similarity in the design discussed here. dVgs must be let to find appropriate level according to drive and output voltage. It cannot be used as a current 'protection'. It is impossible to achieve this goal without loosing linearity and rated power.

The current protection must be done in a different way. Also, it was proven in this thread, that hexfet MOSFETs cannot be paralleled without source resistors. These are 2 basic technical issues of Federman's design.

[PMA]

You are right, Jacco.