ETA: Eh, so does the power adapter (obviously). It's supposed to be 12 Volts.
Tried another 12 Volt power supply (same polarity). My main (folded horn) Speakers sound like they're blown rough and staticy. Even the ones I used to test last time.
....Hmm.
Edit2: The other adapter I used is slightly different. The original output 3 Amps, the other one puts out 2 Amps..... Now I'm wondering if that would account for the buzzing...?