I picked up an old SX-828 at a yard sale. The guy told me 'parts only, don't even plug it in' but of course it powers up beautifully, lights work, etc. Now I want to see if it actually powers anything but I've got these weird speaker plugs that look like outlets. Googling suggests I could just shove speaker wire into the hole for testing purposes. Is this true? I don't really want to spring for the adapters since they cost more than the amp did and I don't know for sure that it's fully functioning.