One more filament raw supply completed today: the 46 driver in filament bias. This driver stage requires 26V @ 1.7A due to the filament bias requirements. Yes, nearly 45W in the filament but will provide a fantastic driver stage with the 46 triode-strapped and filament bias to avoid any nasty capacitor in the signal path.
The power supply design is very simple and follows Rod Coleman’s recommendations for the DHT filament regulators. One drawback in this version, compared to the output stage raw supply, is that this will be pure capacitor filtering with no help of a choke to reduce the input current pulses.
The split-bobbin 150VA transformer provides sufficient current for the capacitor input filtering stage. The DSB10I45 (Schottky 45V/10A) bridge is also mounted on a “L” shape aluminium piece.
The capacitor arrays are soldered to a thick bare wire which provides structure and simplifies connections between components:
I was initially concerned that without shielding the high-current pulses may introduce some noise in the output as F2 fuse is mounted on the transformer frame so the wire is routed back and forward to that point. Reality is that the hum level is very low. I measured 16.4mV peak-to-peak at full load.