[Toka]

I looked but could not find...does the phono stage in an Ultra pre have an AC heater or DC heater? Random thoughts for a snowbound day...

[avahifi_lj]

All of the AVA products in an AVA chassis have regulated DC heater supplies.  Note that the Ultimate 70 uses AC heater supplies.

Thanks for you interest in AVA products!

Larry

[Toka]

Cool...thanks Larry! 

[mark funk]

I don't know that much, I assumed all tubes used DC for the heaters. What is the differences in using DC over AC?

[Dan Kolton]

No chance of the DC heater causing hum at 60hz or some multiple thereof.

[Brett Buck]

I don't know that much, I assumed all tubes used DC for the heaters.

    I would guess that most (and almost all of the "classic" designs) use AC for the filament/heater.

      Brett

[avahifi]

A lot of "classic" designs used AC heaters because inexpensive and space efficient AC to DC supply converters for this purpose were not available yet.  Remember the big stack of parts to do the DC heater supply in the Dyna PAS preamp series?

AC heaters were cheap and dirty, just another tap from the power transformer.

Frank Van Alstine

[mark funk]

Thanks guys that's nice to know I am just learning about these things now at my advanced age. I missed out on playing with tubes and fihi when I was kid, I have a little more time now and I have a PAS 3 all ready for a Super Pas 3 kit and after Frank gives it a clean bill of health I am going to pass it around to a few of my friends I think it mite in lighten them to what real hifi can be.