Wednesday, July 31, 2013

KGSSHV amplifier

An all solid-state electrostatic headamp design by Dr Kevin Gilmore.

There are 2 options for the KGSSHV. Onboard or offboard heatsinks.


Amplifier with Servo:

Mini Power Supply:

Latest silkscreen:

  • Onboard:
Board dimensions(mm): 185 x 123

  • Offboard: 
Board dimensions(mm): 183 x 99

  • Power supply:
Board dimensions(mm): 176 x 167

Latest BOM:
Important notes:

There are 2 ways to build the KGSSHV. Either one with 450V or 500V power supply. 

For 450v version, these are the requirements:
  • Power transformer specs: Pri: 110v/220v. Sec: 2x 420v/130mA, 16v-0-16v/500mA
  • PSU board:  Use 4x 440K resistor ; Total zener diode string is 500V (150v-150v-200v) ; Populate ALL the parts, including the voltage multiplier.
  • Amp board: Use either 2x 2SA1968 (recommended) or 2x IXTP01N100D.
For 500v version, these are the requirements:
  • Power transformer specs: Pri: 110v/220v. Sec: 2x 450v/130mA, 16v-0-16v/500mA
  • PSU board:  Use 4x 487K resistor ; Total zener diode string is 550V (150v-200v-200v) ; DON'T populate these parts in the voltage multiplier section: 0.22uf/1kv cap next to the bias output, 2x 4007 diodes, 15k and 787k resistors, jumper the 0.22uf/1kv cap next to the 300k resistor.
  • Amp board: Use 2x IXTP01N100D only. The 2SA1968 is not up for 500V operation.
Power Supply build notes: 
  • Fuse ratings: it is recommended to use fuses for both Live and Neutral. For 110-115v mains voltage, use Slo-Blo 2A. For 220-230v mains voltage, use Slo-Blo 3.15A.
  • Power transformer can be custom ordered from either (Canada) or (Poland). Toroidy does offer 2 kinds of transformer, standard one or audio one with selected and measured core, electromagnetic shield. They do have more reasonable price and shipping charge.
  • Use either 6x 2sa1486 with the 270v zeners unpopulated or 6x ksa1156 with the 270v zeners populated. Also, either 4x 2sc3840 or 4x ksc5026m.
  • 10m90s devices need aluminum oxide isolator. Also, MUST use nylon screws.
  • FQPF8N80C devices themselves have isolated tabs so no need to use anything with them. Just apply a bit of heatsink goot and whatever screws are fine.
  • Elevate the high wattage resistors (15R/2w and 240k/2w) for better heat dissipation.
Amplifier build notes:
  • Absolutely make sure you connect either Local or Global Feedback jumpers.
  • Adjust the balance trimpot in middle.
  • Adjust the offset trimpot to maximum.
  • Use aluminum oxide and PEEK screws (recommended) wherever needed.
  • Connect the Servo jumper, if needed.
  • Measure everything for short.
Wiring Sheme:

Here is the wiring scheme, superbly drawn by johnwmclean (thanks, John!).
Make sure using 600v teflon wires here, except for signal path.


  1. Don't forget about the jumper for skipping the voltage multiplier? in the case of the 500V version.

  2. Forgot that so I updated the info. Let me know if I missed something, thanks for heads-up :)

  3. 115v= 2A fuse
    220v = 3.15A
    Shouldn't this be other way around?

  4. @Lil Knight -
    Great job with the documentation!
    About time there was a compendium on KG's latest works.


  6. please update the BOM to reflect the need for isolated HV diodes, part # 511-STTH512FP. Don't use the non-isolated parts that were valid fro the older version of the PSU.

  7. This comment has been removed by the author.

  8. Does anyone know if there are board layout suitable for etching own boards for this wonderful amp? All I find is silkscreens and jpgs with all layers on top of each other.

  9. I'd like to see this schematic and maybe roll my own PCB layout for it, but the webserver with the PDFs doesn't seem to be responding.

  10. Hi, links do not seem to work. Would you share the files?