Simplistic Mosfet HV Shunt Regs

[Salas]

Gary already tested a depletion Mosfet Q1 with 500V spec, 840 is already 500V, the cascode BJTs are 300V each. Higher than 68K ref resistors would help also. BUT going to the edge of parts spec is usually challenging them, I can absolutely NOT guarantee the PCB HV creeping distances since its not made and tested for such voltage range.

[10y]

Ok Salas, thank you again.
Ciao,
Anto

[CSlee]

I just tried out a SSHV2 board in a compressor I am buildling. Before I had a pretty good S/N or about -80dB with a pretty basic RC filtered supply, with the SSHV2 board in this doesn't improve at all. I was expecting quite a large improvement... I have no way of measuring the ripple of the first supply other than modelling it, but from what I have read the SSHV2 is in the micro volt region which my supply wouldn't be.

What noise floor are other people measuring with the boards? I am happy with -80dB but thought it is worth asking.

I may need to rework the layout to improve mine, or maybe the circuit has a good enough PSRR for it to not be a factor?

Many thanks

Charlie

[Salas]

If your noise was not of harmonic nature in the first place, then the PSU would have nothing to improve in that aspect. Beyond that, say a phono stage and a line preamp would have a different intrinsic random noise floor regarding self noise and so it goes. To see a general drop it would mean there was a previous white noise like contribution from some PSU that manages to penetrate due to low PSRR, and from a passive its highly unlike. Focus on possible dynamic changes you can sense or not.

[CSlee]

I think I have been looking at it the wrong way - Thanks for the explanation.

I was surprised that I could hear such a difference in my #26 pre with the board in, so I am sure I will be happy with the results.

Cheers

Charlie

[Salas]

Your audio circuit noise floor dominates in other words. Compressor, nice. After that valve soft knee I guess. Vocals? Let us know if it could do some sonic good for it too.

[CSlee]

OK, I think there is still room for improvement so I will look at the layout etc.

I thought it is worth trying out better regulated supplies on classic valve compressors, why should you hifi guys have all the fun!

Hopefully getting some studio time this week so I will report it's performance.

Thanks

[king4joy]

Salas...if you remember, with your help, I have added a SSHV2 to my CCS (C4S) loaded VT-25A line amp. Adding the SSHV2, all hums are gone....however, a light zzzzzssssszzzz....takes over....(which I can live with, although my friends cannot....)....I think this could be because of old tubes.....Salas, what you think??
And with the SSHV2 added, I feel that the music has become a bit restricted...less lively....less fluid.....what I think is I should get rid of the C4S, and instead going back to use resistors to load my tube with your SSHV2.....with a good quality resistor after your board, it should act like a CCS anyway, with the added avdvantage of setting the loading current (voltage across the resistor) easily with your board......
Your board opens up opportunities for me to fine tune my amp with much less fuss and more joys.
Will report back further later....thankyou....

[Joshua_G]

Originally Posted by CSlee

…
I thought it is worth trying out better regulated supplies on classic valve compressors, why should you hifi guys have all the fun!
…

In many cases, the SNR, or noise floor, of various stages, is being determined by the stage itself. When the tubes, power supply isolation from the stage and layout in a certain stage have certain noise floor, the noise floor will not improve beyond the intrinsic noise floor of that stage, no mater what we will to the power supply (other than, perhaps, putting the power supply in a different case and improving the layout).

Yet, the quality of the power supply have great impact on the sound quality, beyond the measured SNR.

Do you know of an HV regulator that may be better than the Salas HV regulator?

[CSlee]

Yes, I think I was just expecting to see an improvement. It is clear that the previous PS was good enough for the circuit with respect to ripple. I will try to improve on the -80dB by changing the layout.

Originally Posted by Joshua_G

Do you know of an HV regulator that may be better than the Salas HV regulator?

No, I did mean that I wanted to try this board as it is one of the best I have seen/heard (but that's not saying much). I would also like to try a Gary Pimm style CCS - VR or similarly Morgan's statistical reg.