When I re-did my home theater a few years ago, I removed the box subwoofer and replaced it with an in-wall unit. I realize that this isn't a suitable replacement, but the goal was to have fewer things for our toddler to bang his head into and fewer wires to pull, so it made sense (I ran a cable to add a traditional sub one day).

Anyway, I've never been able to power it and because life has been hectic I've never even had a chance to configure the speakers properly.

Clearly, my Denon receiver can't power it alone as it only has a sub pre-out. So I claimed my dad's old amp, an Adcom GFA-535 ii. Apparently it's a fairly respected inexpensive home theater amplifier, but it seems like it's not made for subwoofers. I tried hooking up one channel to the receiver and the sub, but the amp acts like there's no input. When I set up the receiver to send a test tone to the sub, I get nothing at all, and the amp's indicators show nothing.

After researching the specs of this amp, it certainly seems to be capable of the frequency range, but I can't figure out what's going on. Any ideas?