Flickering or pulstating Headlights

Lights changing from bright and dim with engine rpm isn't the same condition as flickering/pulsating. With that condition a twitch in amp gauge needle came only with turn signal operation.
I hesitate to mention the mechanical instrument voltage regulators. I suppose a fault in that circuit could show in charging system/gauge even though I've never witnessed. I aint seen it all.
That regulator is supplied by the same wire from ignition switch that feeds charging system and ignition.