Amandarae - Are you sure that you are using the 7518 or is it the 7581? The 7518 only has a 2.5v heater and if that is what you are using you might want to get the fire extinguisher handy. You are right about different voltage requirements but the difference is mainly between the linestage only versions and the full-blown preamp with phonostage. SupraTek owners with the phonostages will have higher current requirements that will restrict the use of some of the lesser rectifiers and pentodes.
Anyone who has a phonestage in their SupraTek preamp might want to check with Mick before rolling power-suppply tubes.
Anyone who has a phonestage in their SupraTek preamp might want to check with Mick before rolling power-suppply tubes.

