If the 12V is constant, it's just like ZM noted. Simply a relay with a 12V coil and contacts rated for the load. A diode should be placed between the coil terminals (line to positive) and you're good. If the 12V is a pulse, you're in the same boat as those using a momentary switch. There are threads/circuits here, Rod Elliott's site and elsewhere as well as really inexpensive flip-flop modules on amzn etc. If you go that route, watch the contact ratings. If lower than necessary You can always throw a more robust relay with that output. Cheers
from my (limited) experience, I don't like anything Jadis
not so judging by SQ (meh) but by simple factor of me being totally and utterly exclusive - 12AX7 is having no place in any amp, at least if not used in some peculiar and novel way**
and that's not the case with Jadis
as fully chromed Harley Davidson
gimme Victory
**for peculiar and novel (sort of) one need to look at Tim De P. constructions, for instance
not so judging by SQ (meh) but by simple factor of me being totally and utterly exclusive - 12AX7 is having no place in any amp, at least if not used in some peculiar and novel way**
and that's not the case with Jadis
as fully chromed Harley Davidson
gimme Victory
**for peculiar and novel (sort of) one need to look at Tim De P. constructions, for instance