Hi Jet,
Elrog seems to favor/recommend DC rather than AC filament voltage for heating. They say that the thoriated tungsten filament due to its thermal properties are more subject to hum with AC heat. I'd get in touch with George(owner)at Tubes USA.com (just to be sure about that). He sells the Elrogs(sold me mine) but also builds very custom tube amplifiers. He's a straight shooter and very knowledgeable. I believe he's located in Long Island NY. I think you'd really these tubes.
Good Luck,
Charles,
Elrog seems to favor/recommend DC rather than AC filament voltage for heating. They say that the thoriated tungsten filament due to its thermal properties are more subject to hum with AC heat. I'd get in touch with George(owner)at Tubes USA.com (just to be sure about that). He sells the Elrogs(sold me mine) but also builds very custom tube amplifiers. He's a straight shooter and very knowledgeable. I believe he's located in Long Island NY. I think you'd really these tubes.
Good Luck,
Charles,