15mA is without the signal. When the stage amplifies some AC the current swings 0 - 30mA in extremes. SSHV does not have any capacitors in the load circuit to smoothe the swings (and it is by design - you should not add a capacitor here!) and there is no source to get this extra current.
... with extreme 70-80Vpp output...
But... this is a line stage.
At 6Vpp output anode swing about +/- 1mA.
20mA shunt easily compensate this +/-2ma alteration.
Yes.
Salas, I am going to use your SSHV2 in place of the 'super-reg' (@250V & 30ma) designed by allen wright for his FVP5A, the last of the series of single-ended preamps he did. I found the super-reg tough to build, although I do have a pair running in another preamp that are stable and predictable. I am going to try your SSHV2 with the lower volt drop (20V yes?) I think I can use a 270-0-270 transformer with a 15H choke and 10uF oil and paper cap for the raw supply. I wondering if you have any suggestions or comments. best wishes, David
You have not mentioned the rectifier type (tube or SS) and the power of the transformer. I doubt you'll reach 270V in the output (250V+20V of overhead) of the raw supply in either way. You should also remember, that SSHV takes another 20mA of current too and the choke has also an active resistance.
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Ok,
Thanks poty,
So, I've got two transformers i can use to get to the 250V & 30ma, a real nice UTC 123 which is 275-0-275 or a hammond 272X 620CT@81ma which is what Allen specified for his raw ss diode supply. I would do the PSUD2, but i don't know the open load numbers for either of these and I will end up with wishful thinking. So given that Allen says there is a 50V drop for his super-reg and the SSHV2 is 20V and working backwards there is =30V to lose. Or I might be able to use the 275-0-275 with a tube reg if i am willing to insert .33-.47uF before the choke to buy a few volts. The tube rectifiers I have on hand are 5839 which has 24v heater, a 6754 and some TV diode tubes, I don't know the volt drop of any of these. With the extra voltage from the change in regs I was hoping to do a tube rectifier. None of this may matter given the noise rejection of the regs. Just trying to make some carful choices where i can.
Thanks poty,
So, I've got two transformers i can use to get to the 250V & 30ma, a real nice UTC 123 which is 275-0-275 or a hammond 272X 620CT@81ma which is what Allen specified for his raw ss diode supply. I would do the PSUD2, but i don't know the open load numbers for either of these and I will end up with wishful thinking. So given that Allen says there is a 50V drop for his super-reg and the SSHV2 is 20V and working backwards there is =30V to lose. Or I might be able to use the 275-0-275 with a tube reg if i am willing to insert .33-.47uF before the choke to buy a few volts. The tube rectifiers I have on hand are 5839 which has 24v heater, a 6754 and some TV diode tubes, I don't know the volt drop of any of these. With the extra voltage from the change in regs I was hoping to do a tube rectifier. None of this may matter given the noise rejection of the regs. Just trying to make some carful choices where i can.
PSUD allows to enter the ohmic resistances of windings to count the open load numbers. The resistances can be measured or obtained from manufacturers' web sites (Hammond has them definitely).
Hi Salas,
I have designed a PCB and built SSHV2 and I have a problem with it. I can't properly change the output voltage from R11 due to D3.
If I eliminate D3, everything is all good.
I have read as much as this this thread as my time allows and I found out about the schottky MBR1100.
I don't have this on hand... can I use any schottky rated at 100Vdc minimum and 2A?
Attached some pictures of my build.
Best regards,
Silviu
I have designed a PCB and built SSHV2 and I have a problem with it. I can't properly change the output voltage from R11 due to D3.
If I eliminate D3, everything is all good.
I have read as much as this this thread as my time allows and I found out about the schottky MBR1100.
I don't have this on hand... can I use any schottky rated at 100Vdc minimum and 2A?
Attached some pictures of my build.
Best regards,
Silviu
Attachments
Hi all 
first of all very thank you all for this project and all helpful information. I just finished my pcb version of Salas. IRF 450 instead of 840. Everything works fine, but I have few questions:
Vin 304.96VDC
Vout on dummy load 207,3VDC (stable after just few minutes); my target
Rdummy 11,47k Idummy 18,07mA
Vacross 10,26ohm 0,2252V --> I 22,5mA
Vgs IRF450 3,09V
Nothing is hot, first DN2540 has normal temperature (warm), IRF450 TO-3 case with typical heat sink little bit warm.
Is 98V not too big? Should I drop more volts on filter section?
IRF450 was used. Wrong choice?
You said 20mA own cosumption, here much more less or I cannot make proper calculation.
Any suggestion?
first of all very thank you all for this project and all helpful information. I just finished my pcb version of Salas. IRF 450 instead of 840. Everything works fine, but I have few questions:
Vin 304.96VDC
Vout on dummy load 207,3VDC (stable after just few minutes); my target
Rdummy 11,47k Idummy 18,07mA
Vacross 10,26ohm 0,2252V --> I 22,5mA
Vgs IRF450 3,09V
Nothing is hot, first DN2540 has normal temperature (warm), IRF450 TO-3 case with typical heat sink little bit warm.
Is 98V not too big? Should I drop more volts on filter section?
IRF450 was used. Wrong choice?
You said 20mA own cosumption, here much more less or I cannot make proper calculation.
Any suggestion?
Attachments
Regarding 98V drop across reg you may use less after you will up the CCS current if the DN MOSFET will become too hot. Depends on sinking.
It looks like you have good sinking for the DN but little for the 450.
IRF450 is slower (more pF) but robust and if stable not too bad for a substitute.
Calculation is easy. I_load+I_own=Set CCS. Although the reg can work to very few own mA, at about own 20mA it shows good output impedance. The more own (shunt) mA the better performance but will also warm up both MOSFETS more. You must make a practical decision.