Some photos of a field coil power supply which has been finished recently.
It is meant to supply a pair of speakers with 3 field coil drivers per side.
All in one chassis.
Completely passive choke filtered supplies, independent for each driver.
Voltages can be adjusted in 5% steps with a common set of switches per section (bass, midrange and tweeter). Digital meters monitor voltage and current of each of the 6 independent supplies.
Adjustment is done by selection of different primary and secondary taps on the power transformers to avoid any regulation circuitry.
LCLC filtering of each of the 6 voltages, so 12 chokes in total.
The finished unit weighs over 50kg!