I just built a small Champ 5f2a, finished it up and started playing it. The amp is very quiet with no hum. Last night it dawned on me that I did not put an artificial center tap on the heaters. Is there any other safety/stability reason to put them in, other than hum control? Because this amp really doesn’t hum! I may leave as is unless I need the artificial tap. Also: the 6.3 winding does not have its own designated center tap.