Simplistic Mosfet HV Shunt Regs

[iko]

Very nice Mr. Disco!

It seems Q2 is working near its acceptable limits, which doesn't surprise me if you look at the SOA.

[Salas]

298V & 460mW. He utilized VCBO and SOA almost all the way. Wise to have done the TO-92 sink. Imagine how it derates in a hot environment near the sinks. MPSA94 is an alternative and it can go near 400V. Those TO-92s keep up decent hfe at 1-2mA we use here.

[albertli]

Originally Posted by Salas

And the higher example.

Salas,

Happy to read through the whole thread and would like to replace the Maida supply with the Reg. above for the 6V6 pre. - your design.

1). I'd use one PTX for two boards and will use MPSA94 for Q2, I have some in hand.
2). Do I have to change anything to optimize the design?

Thanks

Albert

[Salas]

Just set the Reg at 75mA CCS 330Vout R1=27R. If with individual reg per channel, no less than 45mA CCS R1=47R. Lower, it loses transiently. MPSA94 is perfect. Maybe you will need about 20% smaller R5 to get to your needed Vout with the MPSA. Vout slides until thermal stability of the output driver BJT. You will see in practice. Sink it as Disco did, you go high voltage, it needs to be stable. Use the new Russian ''Tungsol'' 6V6GT, TKD 100k pot, and 2.2uF to 3.3uF output capacitor, Mundorf normal supreme. Make an elastically decoupled subchassis for the tubes. Like a TT armboard.

Or you have already made it and you need only to change the reg? If yes tell me more about your experience with it.

[albertli]

Originally Posted by Salas

Just set the Reg at 75mA CCS 330Vout R1=27R. If with individual reg per channel, no less than 45mA CCS R1=47R. Lower, it loses transiently. MPSA94 is perfect. Maybe you will need about 20% smaller R5 to get to your needed Vout with the MPSA. Vout slides until thermal stability of the output driver BJT. You will see in practice. Sink it as Disco did, you go high voltage, it needs to be stable. Use the new Russian ''Tungsol'' 6V6GT, TKD 100k pot, and 2.2uF to 3.3uF output capacitor, Mundorf normal supreme. Make an elastically decoupled subchassis for the tubes. Like a TT armboard.

Or you have already made it and you need only to change the reg? If yes tell me more about your experience with it.

Salas,

Yes, I made the pre-amp, and I just change the PSU this time. Will go with single PTX then to 2 seperated reg. Will certainly post the result after, but please be patient for I'm packing up to move to a new home. It might take some time to make it finish.
The 6V6 with Maida won all the pre-amp I made before. It sounds rich and punchy and with lots of delicate highs. I like the vocals the most with new Tungsol reissue, but didn't have chance to compare with others tubes/brands.

Thanks again

Albert

[Salas]

Won all the pre amps you had? Good news. OK the double 45mA shunt will make it sing even more for sure. Don't you have a picture of the preamp to see it?

[albertli]

Originally Posted by Salas

Won all the pre amps you had? Good news. OK the double 45mA shunt will make it sing even more for sure. Don't you have a picture of the preamp to see it?

Sorry, it's all packed.

Will show you after I have my new audio room set up.

[Salas]

OK, good luck with moving. Use Disco's PCB if you make PCBs, or at least follow its layout as a guide for P2P. Its practical and worked OK.

[Ryssen]

Hello.

Can the circuit in post 3 manage 470v at input with 300v out?

[iko]

I'm just curious, Ryssen, how many mA do you estimate the load to be?