It is based on this schematic:

But parafeed:

Anyone out there also have a project with the FS100PC or FS100PF?

This is the post by Paul Joppa that convinced me to go for it (15 years ago):

Posted by Paul Joppa (P) on February 6, 2009 at 18:41:15
In Reply to: Last call: FS-100 plate chokes posted by mqracing on February 6, 2009 at 08:18:55:

Just a thought for anyone interested ...

In my experience, a larger impedance plate load always makes for better sound in parafeed. I've tried, or at least listened to, a wide variety of chokes as well as current sources. I once built a preamp with switched plate loads of 20, 24, 40, or 48 henries, for example (using 6BL7s parafeed to B7-5K) plus a current source - believe me, every inductance increase was an improvement.

Extrapolating that experience, here's a really wild idea - get a pair of these gapped for 60mA and couple to a TFA-2004Ni with a 27uF capacitor. If you can afford the nickel core TFA (still the best sounding OPT I've ever heard), this choke is neither inappropriate nor unreasonably expensive. Feed it with a 2A3 running 275v at 55mA - cathode resistor 910 ohms - or if you're feeling flush, one of those 2.5v 300Bs at 300v, 60mA (same cathode resistor).

Of course the greatest benefit will be in the bass, so use this to drive some ginormous efficient speakers with killer bass.

I predict you will never hear sound as good with a 2A3.

This was a reply to Mike's last call for these chokes:

On the bright side--- these are really great plate chokes--- and we can airgap them for a range of plate currents--- all of the units are designed to handle 500 vrms at 30 hertz AC signal. DC (plate current) capacities are listed below.

Each unit uses our EL coil design strategy (our SUPER designation). Each unit will be supplied with 18 gauge EE teflon lead wires. Each choke uses teflon insulation. We do NOT formally warrant this choke for high voltage applications. Each choke is wax impregnated. The nominal DCR (winding resistance) of this choke is 170 ohms.

 Amp schematic - Bas Horneman 00:25:31 02/20/24 (4)
 RE: Amp schematic - boatshed 05:53:48 02/21/24 (3)
 RE: Amp schematic - Bas Horneman 02:26:52 02/22/24 (2)

...

Show full thread outline!

 Amp schematic - Bas Horneman 00:25:31 02/20/24 (4)
 RE: Amp schematic - boatshed 05:53:48 02/21/24 (3)
 RE: Amp schematic - Bas Horneman 02:26:52 02/22/24 (2)
 RE: Amp schematic - boatshed 06:07:20 02/22/24 (0)
 RE: Amp schematic - Bas Horneman 02:27:21 02/22/24 (0)
 Power supply schematic - Bas Horneman 00:23:04 02/20/24 (0)
 RE: Almost done 2a3 parafeed with Magnequest FS100 PC 60mA/120H - Bas Horneman 08:13:06 02/16/24 (3)
 I will say - Story 08:45:48 02/16/24 (2)
 Better! nt. - Bas Horneman 09:23:23 02/16/24 (1)
 Just kidding. Beauty is in the eye of the beholder - Bas Horneman 04:02:27 02/18/24 (0)
 During times like this I was Mike was alive. Why did I wait - Bas Horneman 04:05:09 02/16/24 (0)
 With tubes. First smoketest passed (ht off) - Bas Horneman 07:15:34 02/15/24 (0)
 RE: Almost done 2a3 parafeed with Magnequest FS100 PC 60mA/120H - boatshed 19:30:39 02/13/24 (3)
 It was a one off series in 2009 - Bas Horneman 00:48:08 02/14/24 (2)
 RE: It was a one off series in 2009 - boatshed 08:54:27 02/14/24 (1)
 RE: It was a one off series in 2009 - Bas Horneman 23:09:12 02/14/24 (0)

Mike also did a FS100PF output and matching plate in 2006.

ps. I replaced the us brass bolts and nuts with metric size m5 brass

The white is RAL 1015 (Light Ivory)