.....I'd do it the way PS Enginering says! My audio system has been perfect (done with shielded wires per their manual), with no whine or hum at all. Perfect, that is, until this weekend when I plugged in my MP3 Jukebox for the first time. You guessed it - got a hum! I can plug the stereo cable into the airframe jack, and no problem, but when I plug the other end into the Jukebox - Alternator whine (if I kill the alternator, the whine is gone)! It's not really that bad if I turn the music up, but that's not good for the ears!
Anyway, I talked to PS Engineering yesterday, to see if there is a "simple fix" (A filter or something), and alas - no dice. It's all magic, and probably has to do with a floating ground somewhere. Bottom line - do the very best you can to follow the installation manual to mimimize the chance of noise in the system. You're not going to know you have a problme until you are flying (you can't test it "all-up" until the wiring is finished), and at that point, fixing a wiring problem is WAY too hard....
I have much respect for Bob Nuckoll's and learned a lot from his book, but in the end, he doesn't have to fly your airplane - and you do!
I am going to check the easy stuff - the ground potential at the airframe jack - and then live with it (at least until I decide to upgrade to a stereo intercom...there's always more money to spend!
).
Paul