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another question: What are differences between the Triad C7-X and the Hammond 193C ? Is there a better one ? ...
Well they are both chokes LOL ... The 193 weighs more than three times as much, has twice the inductance and a similar current rating, has 2/3 the DC resistance, it's enclosed instead of open frame, and it's mounted vertically. Costs a lot more, too.
Incidentally, I believe the current-production C7-X is in fact made by Hammond, to the original Triad specs (more or less). The original was chosen back in the days of the original S.E.X. amp (we are fast approaching the 20th anniversary of that seminal product!) because it was available from Allied at significantly less cost than other chokes of similar specs. It's been a go-to workhorse for Bottlehead in several applications, mostly because it works and we know its foibles.
Fortunately, a power supply choke is not usually a critical component. For Crack, you want a current rating of 70mA or more, and probably a DC resistance of 200-350 ohms to keep the power supply voltage pretty close to original. I don't think either PB (the designer) or I have actually modeled a choke power supply for this application, so no comment on the best inductance. There have been discussions on how to model power supplies, and what behavior is best, at the Tube-DIY Asylum. But go there with your cynicism intact and post wiht your flame suit on - there is a LOT of misinformation surrounding the good stuff, and people get pretty excitable on the subject.
