An amplifier does one job: it takes a small signal from your mixer and makes it powerful enough to move your speakers. Getting the pairing right protects both pieces of equipment and gives you clean, loud sound.
Watts and headroom
Choose an amplifier whose output at your speaker’s impedance is a little above the speaker’s continuous power rating. That headroom lets peaks pass cleanly instead of clipping, which is what usually destroys speakers.
Understand impedance
Speakers are rated in ohms, commonly 4 or 8. An amplifier delivers more power into a lower impedance, so always read its specification at the load you will actually connect. For example, the Great Sound CA-4000 is rated at 1600 W per channel at 4 ohms and 1000 W per channel at 8 ohms.
Stereo, parallel and bridge modes
In stereo mode the two channels work independently. In parallel mode one input feeds both channels. In bridge mode the two channels combine to drive a single load, which increases available power, 2800 W in the case of the CA-4000, but requires a speaker that can handle it.
Use a crossover for subwoofers
A low-cut or subwoofer filter lets you split a system so that subwoofers handle the low frequencies and cabinets handle the rest. This keeps the sound cleaner and protects small speakers from deep bass.
Cooling and installation
Power amplifiers generate heat. Leave airflow around the rack, and use proper speaker cable and connectors such as Speakon for safe, secure connections.