Most midrange and high end receivers have a set of jacks on the back labelled "pre-amp out" or pre-out for short, with one jack for each channel. You run RCA audio cables from the pre-out jacks for the front left and front right channels to the line-in jacks on the power amp, then disconnect those speakers from the receiver and connect them to the speaker-out terminals on the power amp.
Adjust the volume on the power amp until the speakers play at the same level they did before. At this point you will be thinking "same level... so what did I just accomplish ?".
1. Normally the main and center speakers have to play the loudest, so those channels are the ones where your receiver will run out of power first. Bigger amp = they don't run out of power so soon.
2. Since the main speakers are no longer connected to the receiver, they are no longer presenting a load to the power amp stage of the receiver and no longer consuming power from the receiver's power supply. As a result, there will generally be more power available to the other channels, ie they will be able to play a bit louder than before while still sounding clean.
3. If you are running M80 mains, they present a 4 ohm load which some receivers don't like, while all the rest of your speakers will typically be 6-8 ohms. Big-ass power amps seem to handle 4 ohm loads well, so as a result you have a bit more flexibility in choosing receivers, specifically some Yamaha and Pioneer models which are real nice except that they don't always like driving 4 ohm speakers.
Edited by bridgman (08/01/06 03:34 AM)