I studied solid state electronics at TAFE for a couple of years and I'm the state rep for Mobile Electronics Australia (Formerly Car Audio Australia).
I also Judge CAASQ (Which is the National Car Audio Sound Quality Competition)
And I compete in dB Drag Racing - which is the International competition format for SPL (sound pressure level) or basically a competition to see who is louder at frequencies below 80Hz
which if you know anything about impedance loads (and rise and fall) and current you can understand why I know what I know and why I have more "real world" experiance than "text book" knowledge. I also as a result of my personal interest in Car Audio and associated electronics have a lot of freinds in the industry so I have been involved with many show cars including motorisation or doors, boot lids, bonnets etc as well as low current lighting etc.
I also have been involved in Pro Audio and Pro lighting since i was 14 and I have been a front of house audio engineer for crowds as big as 14,000 people
So I try to help where I can with the knowledge I have gained over the years.
As for a power pack to supply the power for the radio - essentially a battery charger is just that. But all chargers and unless you spend big dollars on a power supply will have a 50hz ripple as thats the frequency that AC power alternates at in australia.
A battery will use its natural capacitance to filter the ripple - but differnt batteries will react differently.