Regulated filaments can be tricky to design. It's the one area where PSUD is not as accurate as you might wish, due largely to the inaccurate diode models. You may need to use a Schottky diode rated 15 amps or more. Then you need to subtract the peak ripple voltage from the average DC voltage to keep the regulator from dropping out. I subtract another 10% to allow for power line fluctuations. And the DCR of the transformer (including the reflected primary DCR) adds to the series resistance. And the high voltage winding rectifier/filter adds to the primary voltage losses.
Certainly seems that way. I have by far the least experience designing anything power supply related. Just not something you come across in mechatronics much unless you are designing large scale industrial, which I don't. And even then it's pretty much just IDing COTS stuff that fits the bill.
I may just slap the PT-2s I have left in these SR-45s and experiment with the PT-7s more when I do my Paramour rebuilds.
I currently have some 6BX7 amps powering the horns in my upstairs system and it's making it near impossible to find a good crossover point. They just sound completely different than the Paramounts powering the woofers. And seem to exaggerated the beamy-ness of the 500b horns.
So I kind of just want to get these built to get the 6Bs out of my upstairs system.