It's cheap, it's N, it's dirty, it's.... The CIRCLOMOS!!!

[Elvee]

I should have made clear that I was looking for very high voltage devices. In this respect, the SJEP170R550 from Semisouth is marginally better than the ST.
For the small to medium power bipolar, I was trying to find something similar to the BUX87, but higher voltage, and more suitable for linear operation.
Thanks for the pointers anyway, the SiC looks promising.

[tiefbassuebertr]

I recall to some BjT high voltage types from Shindengen but on the currently website I don't find such types:
Home | SHINDENGEN ELECTRIC MFG.CO.,LTD
perhaps there you will find appropriate types:
Description TRANSISTOR, TRANSISTOR Datasheet search, TRANSISTOR datasheet, TRANSISTOR datasheets, TRANSISTOR data sheets - ALLDATASHEET.COM
the follow is made prefer for switching application (HFX Series):
http://www.datasheetcatalog.org/data...gen/mXrwvs.pdf
but the question is whether it is only suitable for switch applications

There are some other HV BjTs, but except the MJ16018 MJ16018 pdf, MJ16018 description, MJ16018 datasheets, MJ16018 view ::: ALLDATASHEET :::
I don't know types for linear applications:
2SC3996 pdf, 2SC3996 description, 2SC3996 datasheets, 2SC3996 view ::: ALLDATASHEET :::
BUH1215 Datasheet pdf - HIGH VOLTAGE FAST-SWITCHING NPN POWER TRANSISTOR - SGS Thomson Microelectronics
BUY71 pdf, BUY71 description, BUY71 datasheets, BUY71 view ::: ALLDATASHEET :::

[tiefbassuebertr]

by post #32 about
Successors for V-FET SONY-Yamaha-TOKIN 2SJ28, 2SJ18/2SK60, 2SJ26/2SK76 and 2SK180
there are informations about various patents concerning SIT's - perhaps also of interest here

[tiefbassuebertr]

Originally Posted by Elvee

This my final (lab) version, including a latching protection.
I am currently adapting the topology for very high voltage output (>1KVpp).

could you perform a stability test so as an audible test already?

[Elvee]

Here is a plot of the loop gain:

[tiefbassuebertr]

here a solution for a passive phase reverse stage (i. e. with interstage transformer resp. driver transformer instead a totem pole common emitter or emitter follower topology):
F6 Amplifier

[Elvee]

Originally Posted by tiefbassuebertr

here a solution for a passive phase reverse stage (i. e. with interstage transformer resp. driver transformer instead a totem pole common emitter or emitter follower topology):
F6 Amplifier

It takes me back 40yrs: I remember building such an amplifier, transformer-less output based on AD149's, and at the time I found the sound amazingly good...