Yep, i read a similar article recently about turning down the gain of the audio amp.

As much as this 'bandaids' the problem, it's not really a fix.

There's still a reason WHY the amplifier (at original high-gain) is so succeptable to picking up the hum and passing it thru.

Call me old fashioned, but i like to ELIMINATE problems, not cover them. 

MM.