Regulated heater voltage in mics (specifically, U67)?

[OneRoomStudio]

I tried doing a search, but I couldn't come up with anything super conclusive. I've seen a few people say they don't like regulated heater supplies in tube mics, especially U67s, but I can't find a reason why. The heater is negative in a U67, so a 337 needs to be used instead of a 317...no problem there. Regulators can introduce some noise, but regulating a volt or so below -6.3V (i.e. -7.5V) and then doing some additional RC filtering should solve that. It can't be an issue of current supply, since we're talking about the heater, not B+, and besides, it's easy to build a circuit that can supply plenty of current. So....what's the issue?

 

[mihi_fuchs]

i had no issues regarding my u67 build and used the lm 337 for the negative heater voltage.
however i had issues using the regulated psu for the u47. got some quite good explaination - see here:
Post in thread 'D-EF47 Tribute To Oliver Archut U47 Build Thread.'
https://groupdiy.com/threads/d-ef47-tribute-to-oliver-archut-u47-build-thread.56878/post-1010514

however you are right - in the end a cathode bypass in the u47 build did the job (https://groupdiy.com/threads/u47ef-oliver-archut-version.84508/post-1097400).

nevertheless - in my u67 the regulated psu worked fine.

hope that helps,
best regards and a nice evening

 

[Khron]

I can't find a reason why

That's because there isn't one. Well, not outside of confirmation bias and other such "mental issues"