Ok, so I suck at electronics; I am learning but please forgive me if everything I say in this post sounds totally stupid. The project I am working on requires that I drive an electromagnet (~ 3 - 5 ohm) from a fairly small logic level input signal, -5v to +5v, 250 MA. I would like the output signal to be on the order of -24v to +24v 20A continuous output. While I think this project is similar to an very big audio amplifier, I am in fact not driving a loudspeaker. The general gist of the project is to drive ferrous objects (not speaker cones) in time to music. A simple example would be making a iron ball on a string swing back and forth in time to the bass signal in a song. Because the output of the system is not a sound wave, I don't care very much about distortion at all. What I need is a simple push-pull amp design with gain, gain, gain. From my early electromagnet experiments I have realized that because of the inverse square law moving objects from any distance at all requires a very powerful magnet. To give you some idea, the power supply I made for this project is built around this transformer. And yes, I realize that pushing 600 watts continuously though a electromagnet is going to get very hot very fast. The electromagnet is liquid cooled. I am slowly making my way through "Designing Audio Power Amplifiers" by Bob Cordell but it dense material (for me a least) and I am having trouble figuring out what exactly I can/can't do without. My questions are: What is the simplest circuit I can get away with? What transistor / FET pairs can handle this sort of power dissipation even with a cooling fan? Thank you for any help you wish to offer, even if it is simply to tell me that I am going to electrocute myself.