What would it take to balance a stereo power amp ?


I am in a band and own the P.A. system that we use . In the interest of eliminating hum and noise I have decided to run it balanced . The main FOH system is tri-amped with an electronic crossover going into three seperate stereo power amps. Two of them have balanced inputs but one of them does not . The "unbalanced" amp is an older model that has given me years of trusty service and I don't want to replace it if unnecessary to do so . What would it take to balance it ?
Obviously , it would have to be an inexpensive retrofit or it wouldn't be worth the cost or aggravation . Any help would be greatly appreciated .
dicehead
Opinions may seem to be divided but Nrchy is correct.(1) You cannot easily balance a non-balanced amp but (2) you can make it compatible with balanced sources.

You also ask: "Does any one know of a circuit diagram or a place to come up with one ?" Assuming you mean adding an input transformer for (2), others will suggest specifics. If you mean (1), then you have to tell us what the amp is and provide the original schematic.
Of course, I'm sure you realize that I wasn't inferring that adding the adapters would change the topology of the amp to balanced. The adapters are simply a way to allow him to use the cabling he wants.
Dice
This might be a nice site to visit should you want to DIY.
http://www.epanorama.net/links/audiocircuits.html