Quote Originally Posted by RothwellAudio View Post
PSRR stands for power supply rejection ratio. Without getting too technical it's basically a measure of how well an amplifier shrugs off the inadequacies of a less-than-perfect power supply.

BTW, going off at a slight tangent, I think it would be helpful for people not to get too hung-up on the "power" side of a power supply and instead think of it as a voltage supply. Sure, for power amps it's important to have some power available, but mostly it's a steady voltage which is required. Actually, that's still true for power amps - but the voltage needs to hold steady under more demanding conditions.
Anyway, the idea that a "good power supply" means one which will supply more power - and is therefore big - is over-simplistic in my opinion.
Yes, indeed a PERFECT VOLTAGE SOURCE is what we seek. This implies the capability to give infinite power of course since P = Vsqrt/R so if R = 0 power is infinite.

Now obviously this isn't possible... and even less practical or affordable! What a good linear regulator does is make the power supply behave as if it has infinite power...... up to the point where it goes bang and releases the magic smoke installed at the factory in every electronic component... or if it's competently designed goes into current limit and saves itself. So long as we don't require more power, ie current draw, (Power = Volts x Amps also of course, or so Mr Ohm says)) than the regulated PSU is designed to supply, we have a near as damn it perfect voltage source. Perfect voltage source = zero output impedance = infinite power, should the load try to draw it. The balance of compromises chosen in chasing but never reaching perfection applies to linear regulated power supplies as to everything else of course!