diytube.com

Stumbled across this video today. Seems like I need to find an oscilloscope.

I wonder how much audible hum coupling caps introduce into amps, if at all.

https://www.youtube.com/watch?v=BnR_DLd1PDI

Cripes, we forumers couldda explained that in 5 minutes

Just use a phono stage with test leads. One direction will be hummier than the other. No scope needed

I remember an article in Dutch journal Elektor Electronics, describing a polarity tester. The idea was find which lead was connected to the outermost capacitor metal foil. By connecting that lead to a point closest to ground would minimize hum pickup.
Haven't got the article but still .... do I care?