I just picked up a Duncan 84-80 that all of the parts are in reasonably good looking condition but it has obviously been jacked around on. The speaker is missing as are the tubes. I tried to download a PDF of the owners manual and cannot get it to open. So, I need help with a few things. I have a schematic of it, and it appears that one of the two output jacks goes to either a 4 or 8 ohm speaker, is that right or should there be a 3rd pair of wires coming from inside the chasis apart from the two jack outputs? Also, do you know what impedence speaker it came stock with, and can an external cab be added to the other jack ( does it have internal impedence matching?). Thanks for any info you can give me about it.