Arny Krueger wrote:

When you were designing power supplies, did you use 12 volt transformers to
produce 12 volts DC regulated, or did you throw in a safety factor?

I never went as low as 12V.

15V was my lowest ever and for several recent decades I was using +/- 17V for
extra headroom.

Of course do you mean the O/C transformer voltage ? With the lossy but very low
field R cores I was speccing up to 25-0-25 O/C IIRC to get a well regulated +/-
17V.

We did test them down to 208V for 'low line' operation though. Never had more
than a few hundred uV of audio band noise on the rails.

Graham