That's true. See www.w0btu.com/miller-larson_effect.html 73, Mike www.w0btu.com On Thu, Jan 29, 2015 at 11:36 AM, Gerald Williamson via Amps < amps at contesting.com> wrote: > Manfred, you can be sure that tube life is adversely affected by frequent > on/off cycles of the filament. >