Electronics > Projects, Designs, and Technical Stuff
It looks for me as stupid schematic (Oldtimers welcome!)
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T3sl4co1l:
The capacitors are laughably oversized, more a liability than any electrical benefit.  It won't handle a short for very long but I think it will actually survive one momentarily.

Yeah, it'll perform better -- not to mention be cheaper to make -- with a zener.  Less bias current needed, too.

Tim
schmitt trigger:
One aesthetic advantage of the 0A2 tube vs a zener diode, is that they have that gorgeous glow that only a gas discharge produces. For those of us which look into the aesthetic looks of tubes, it is beautiful.

On the other hand, the breakdown voltage changes with ambient illumination. And parallel capacitance should be limited to less than 0.1uF, otherwise the tube will start motorboating. These characteristics are described in the linked datasheet.
Plus they are significantly more expensive.
SiliconWizard:

--- Quote from: schmitt trigger on October 03, 2019, 03:34:52 pm ---On the other hand, the breakdown voltage changes with ambient illumination.

--- End quote ---

Ahah yeah, that's part of their charm. Like they also have a "microphonic" behavior. They are susceptible to vibration and shock.
001:

--- Quote from: SiliconWizard on October 03, 2019, 04:04:24 pm ---
--- Quote from: schmitt trigger on October 03, 2019, 03:34:52 pm ---On the other hand, the breakdown voltage changes with ambient illumination.

--- End quote ---

Ahah yeah, that's part of their charm. Like they also have a "microphonic" behavior. They are susceptible to vibration and shock.

--- End quote ---

Very strange design for REGULATOR circuit  :-//
floobydust:
We don't know the requirements for voltage and especially output current.
For audio applications, these are HV regulators to get of line and load variations, and absolute voltage is not critical. 1% regulation at 400V is 4V so 396V or 404V is not a problem. I find low noise is harder to get.

Don't tell anyone but I've used 0B2, 12AX7 and 6LC/6550 and no drama there. About 550VDC input and 350VDC output to over 300mA. I had the parts lying around decades ago and thought it would be fun to learn as a teenager.  Otherwise I use a simple BJT and zener with CCS for low current loads, say under 50mA.
OP's circuit is missing a dedicated (floating on high side) filament winding for the pass tubes, which is an extra expense.

These HV regulator threads always end up in a flame war of solid-state verses vacuum tube (pass device) because people want unrealistic output currents in a $5 circuit with a handful of parts. Solid-state HV regulators in the few hundred mA league need many parts, SOA and current-limiting to be tough and reliable. They are dangerous to develop on the workbench and unforgiving of mistakes. There is no simple circuit out there that is 100% solid-state. Sorry but that fantasy has to end, so we end up with these hybrid designs.
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