Simplistic MosFET HV Shunt Regs

[Salas]

Can you define the low ripple roughly, as in the prototyping what were the incoming incoming ripple roughly (per sim like psud) ? I think I remember we discovered that SSHV1 did better with more pre-filtering than initially thought.


As far as the earlier post regarding using this reg with a CCS, I remember reading one of Olsen's presentations where there was a benefit to using a shunt reg before a CCS as far as isolating the music signal from the power supply. But remember you will lose 20V's headroom just inserting the reg, which may in many preamp designs be too much to allow the CCS to do its job. But most likely the 20V's can be gained back via loosening up the pre-filter in an existing design. But we probably need to nail down the max incoming ripple a bit (I imagine is depends on the load and shunt current.)

You mentioned some prefering CLC to CRC. One last question, does the output impedance of the prefiter matter at all?

10V is the safe limit. 20V we give for good measure not to underachieve with some Tx tolerance and/or mains drop during the day.

As for 120Hz ripple don't expect it to really pass, its more a matter of general grounding quality and absence of hum fields. See a Spice attachment for 30VP-P 120Hz ripple (blue) and output (green). From experience, the rectification's HF harmonics penetrate much easier like X rays any practical build through numerous parasitic paths. I don't think that any CCS is better firewall than a ballast resistor regarding such gremlins. That is why a basic CLC and not more than 200mV RMS AC riding Vin on the scope is a good rule of thumb. This CCS is cascode with smallest stable gate stoppers so to hold high well, but it won't surprise me if the rectification and filtering quality is possible to could be picked up still as a deeper black background or enhanced HF flow. Has a lot to do with the audio application's PSRR too. The output impedance of the pre-filter should not matter.

 

[king4joy]

what is a ballast resistor??.....where should I put one??....I do have a bleeder resistor in the PSU...

 

[Salas]

Don't worry, has nothing to do with the schematic.

 

[king4joy]

Reading your post #2061, you mentioned MJE350 can be used....but I am less sure from the reading if you are referring to Q3 only or Q4 and Q5....

 

[Salas]

Q4 & Q5. Not Q3.

 

[king4joy]

I thought so....and thankyou for confirming...

 

[dadedady]

Very helpful PCB. I'm thinking to move Q1 at the same side of IRF840 to use a heatsink for both

 

[Salas]

Vgeorge had tested like that also initially and it had worked.

 

[dadedady]

Heatsink for Q2 ? Ithink no

 

[vgeorge]

Heatsink for Q2 ? Ithink no

Not necessary, if you look at my last layout previous on this thread.

 

[dadedady]

Thanks. And a last question (I hope). For C2 10uF is the optomum, 15uF the up limit, The down limit?

 

[Salas]

Keep it at 10uF. You could make do with a 4u7 for a while to test.

 

[dadedady]

Then 10uF electrolytic plus // 1uF MKT, because I can't find MKT or MKP and I don't like to buy from ebay
Thanks again Salas

 

[AndrewT]

Try MKS. It usually has a higher esr and that combined with a "normal" electrolytic (not low esr) may just be enough to damp oscillation.
Maybe the electrolytic on it's own might work well enough.

 

[dadedady]

Thanks. I'll try

 

[Tea-Bag]

Looking at Erse, SCR and Solen caps, for a good fit.
Of course box caps lend themselves to the board layout mentioned, but seem harder to find in that value and voltage.

 

[king4joy]

Then 10uF electrolytic plus // 1uF MKT, because I can't find MKT or MKP and I don't like to buy from ebay
Thanks again Salas

Please let us know if 10uF electrolytic or any combination of bi-pass will work here.....electrolytic is cheaper....

 

[Salas]

Will work less transparently in tone.

 

[king4joy]

Would that be more transparent, or less transparent than without using SSHV1 or SSHV2??

 

[Salas]

Both those versions highlight the use of plastic capacitors. If you will use an elcap in the voltage reference filtering position you will enjoy less transparency in both.