I haven't found that the hum got any better with different brands/types of tubes. it was always present for me.
Here is a schematic for DC Filaments from a mesa Mark III they just used a bridge rectifier and a capacitor right on the 6.3 taps. you wouldn't have to add much to test it.
Here is a schematic for DC Filaments from a mesa Mark III they just used a bridge rectifier and a capacitor right on the 6.3 taps. you wouldn't have to add much to test it.