@Arthur P. Bloom posted:And the third is a telephone butt set, (an old analog desk telephone set will work) combined with a well-trained human ear.
Arthur, you made my day.
I sat here for the past two hours trying to think of number 3 and came up short.
Listening to detect the quality (purity) of the DC output? Excellent idea!
Buzz, pops and clicks, and several other things would indeed be detectible this way, everything but slow changes in voltage or artifacts too high in frequency to hear.
Thanks.
Mike
