[Brian Krashpad]

Yeah, you would either have to have a mixer and power amp, or get a little multi-channel PA head like that Behringer. There are used Peavey PA heads that are 5 or 6 channels all over the place for next to nothing. I have an old one that I use as a PA head for band practices or small gigs, but in that situation I use it for vocals only and the instruments use their stage volume from their respective amps.

But they can also be used the way you suggest. In fact, right now for my church gig I'm using that same Peavey PA head for both guitar and mandolin, so that each can stay plugged in, and I don't have to unplug anything to switch instruments. Plus each channel can have different volume and tone levels. You'll need some type of speaker cabinet as well. At church I use an old 1x15 bass cab so that just in case I have to play bass rather than guitar or mandolin, it'll be able to cope with the signal without blowing up or farting out.