It is a massive 4 choke supply. I believe many of the commercial tube preamps or even power amps don't even come close to this! Pseudo mono power supply is used to split the left and right channel B+ with chokes to reduce inter-channel crosstalk. Do remember this is a preamp and ripple on the B+ is highly undesirable, therefore the power supply has to be carefully designed. All the chokes have to be at least 20H 150mA for the 1st two, and 20H 80ma for the other 2. Since there is no output transformer used, the size and weight should still be bearable.
The filament supply for 5687 is AC and for 45, it is a special voltage-current regulated 2 stage DC supply. 5687 filament's supply is AC as it is indirectly heated. DC supply for 5687 is just an overkill. Some claim using DC as it reduces hum on indirectly heated tube, that's just plain BS as they do not know how to design a good power supply. As for directly heated tubes, this is another matter. For power amplifiers, AC heating on tubes like 300B (5Vac), 2A3 or 45 (2.5Vac) is still okay if users have medium efficiency speakers. For those with 94dB/w/m or above speakers, DC heating is a must to kill the AC hum. For preamps, DC is a must on directly heated triodes with whatever speakers.
Alright, that's all for PSU. Next, we're going to talk about parts... this is the interesting part... :)
