Why would you want a separate amp and preamp when you can get a receiver that includes both functions? The short answer is that you can get better sound and more system-building flexibility.
Below you find some tips on how to choose. For more info, read our guide to separate amps and preamps.
A stereo preamp includes connections for your source components, as well as tone, balance, and volume controls. There's a switch to select the component you want to play.
Think of a surround sound preamp/processor as a home theater receiver without the built-in amplifier. It does the video processing, surround sound decoding, input switching, and audio signal processing.
Hi-fi stereo amps are for high-performance stereo music systems. They can be used in surround sound systems, though multi-channel amps might make more sense for that purpose.
Monoblock amps have just one channel. Some models are designed to drive a passive subwoofer. Others are meant for audiophiles who like to use a separate amp for each channel of their system.
Multi-channel home theater amps are the companions for surround sound preamp/processors. You'll need at least five channels for a surround system. You can choose a powerful 3-channel amp to drive the front left, right, and center channels. Your surround speakers, which may require less power, can have their own 2-channel amp. If you want to keep things simple, get one amp with enough channels to drive all your speakers.
Multi-zone amps are building blocks for a multi-room system. You get at least two channels of power. Some models include as many as 16 channels. Many models include connectors for remote control, power triggers, and infrared signal transmission.
How many watts do you need? Wattage ratings and maximum volume are only loosely connected. For example, a 200-watt amplifier will only play a mere 3 dB louder than a 100-watt amplifier — a barely noticeable difference. To play twice as loud as that 100-watt amp, you would need one with 1,000 watts, a ten-fold increase in power. Look at the recommended power range for your speakers and choose your amp power accordingly.
Most preamp-processors and a few stereo preamps include a microphone and a built-in app that automatically fine-tunes the sound to suit your listening room.
Many preamps have network connections that let you play streaming music services or music stored on a computer or hard drive.