04-30-2018, 09:44 PM
Shelf space was more important than tube life way back when. The "vent" panel on top of amps and combos was minimal. Yeah, a "whisper" fan or one from a discarded PC power supply helps a lot, and the 7591's will go on for a while. Probably could sub some bigger and more commonly available pentodes if width allows and height no longer a problem when it becomes necessary.