I have my whole house wired for sound (about 8 pairs of speakers throughout the house). I have a receiver hooked up to two of these sets, but was told it would be a fire hazard if I tried to stack more into any of the inputs and needed an amp. I'm looking to do this as cheaply as possible. Do you have any suggestions on amp options?
Keeps the load of the connected speakers within the acceptable range of the amp, typ. 4 ohms or higher. Without it, you risk the amp seeing too low of impedance which, best case, the amp gets hot and shuts down. Worst case, it gets hot, is damaged as a result, and goes to the scrap heap.
Just because there is a knob doesn't mean you should turn it.