N_Cook wrote:

Looks like a regular linear ps to me except for the transformer being about
4 times the size necessary for a preamp and relays - more superfluous
weight.
Pair of 3300uF caps , 78M18,79M18, 5V reg , no chokes, no mu-metal or
anything noticeably odd but, at least, no gold plating.

I was wrong in calling it a "very clean power supply". I should have
said "it has the effect of a very clean power supply"....

Have a look around the preamp section. As from the link I gave (from
google), it's not a regulator but an "active filter".

Quote "tracks input voltage as changed by variations in line voltage and
load, and takes out some AC. That may be useful under some special
circumstances. In the tube days, this was done using a large choke,
that's in a way what this circuit simulates."

FWIW I tried a patent search. Got nothing.

--
Adrian C