I'm still on my quest to build a large an powerful electromagnet. I'm wondering if I can put a non oscillating signal in one of the RCA jacks if my old crappy, "don't care if i blow it" amp will amplify the signal. Also how can I put in a non oscillating signal? Would a 1.5 volt battery work?

I'm not really following the logic here. To build an electromagnet, you just need a beefy power supply to apply current to a coil. The whole amplifier is completely unnecessary.

I used to have a larly large, very strong electromagnet that ran on 12 volts, but I have absolutely no idea where it is now. I hurt myself many a times on that thing. Lots of fun!

Ah ok, I need to be able to adjust the current which an amplifier would do well. I could just put a potentiometer between power supply and it.

I have a question for you, what type of power supplies would be best?

Really, anything cheap, that can deliver the required amount of current. Check your other thread, I posted a place that seemed to have a reasonable (IMO) price for electromagnets. Once you have one picked out that you think will be powerful enough, a PSU can be nailed down.

Ah ok, I need to be able to adjust the current which an amplifier would do well. I could just put a potentiometer between power supply and it.

I have a question for you, what type of power supplies would be best?

I'm not an expert here, but I really don't think that a regular pot would like the kind of current that would be going through it if you use it this way.

I'm not an expert here, but I really don't think that a regular pot would like the kind of current that would be going through it if you use it this way.

Got that right. I'd probably PWM a Mosfet H-Bridge, if it were me.

Yeah, audio pots typically don't like a bunch of DC on them. Non-oscillating = 0 Hz = DC. If your amp is DC coupled it likely will amplify DC. It may not like it much though, as I would think it is a very hefty duty cycle (100%)?