Metropoulos Forum

Hello, anyone know anything about DC heaters in high gain pre-amps. What do i need, just some diodes on the regular filament wiring?? Full wave? Half Wave?
mike..

I don't think modding an amp for DC on the preamp heater fillaments is worth it. The difference in hum is minimal in my experience; I have several amps, some with and some without DC fillaments and there isn't much difference. Most preamp tubes are run in a humbucking mode anyway, even with AC fillaments.

Careful tube selection will make the most difference in reference to hum and noise. Just be sure you don't get Sovtek 12ax7LPs (if you have to use them get the LPS version instead).

If you really want to go ahead check schematics for Marshall DSL or Rivera amps for examples of DC rectified heaters. Both use Full wave rectifiers, probably because they're just as cheap.

Good luck

thanks rjgtr,
the reason i was thinking dc is because i am designing this super high gain preamp for a friend of mine, so far it has 6 cascaded gain stages. i thought dc heaters would cut down on the oscillations and other screeching noises, but if they dont make that much difference then i wont worry about it. I appreciate the wisdom.
mike