Could any electrical engineers here explain how one gets both +12V and -12V output from a +12V input?
I assume the PSU isn't making -12V from +12V. It's making both of them from whatever the AC is
Voltage is just your distance from ground, and while we generally think ground has 0 volts, really it can have any number of volts, just whatever circuit you're running is higher. Voltage is relative to the ground potential.
To put it another way, voltage is pressure in flowing water. If you pick a river as "earth" 12V is whatever 12V is in speed faster than the flow of the river, and -12V is going the same amount slower than the river. The river is your ground potential
Without the -12V, the silent sections in the music just isn't as airy.
http://www.ianstedman.co.uk/amiga-power-supply-guide/
> What is the -12V supply on the Amiga used for?
> It is used for the RS232 transceiver chips and to power the Op-Amps in the audio circuits.
So the Amiga's audio just won't have that oomph without that -12V power.