The amount of power needed for your home-theater receiver depends, in part, on the speakers you choose. Given a certain amount of power, different speakers have different sensitivities, a measure of how loud they are.

The standard measure for speakers' sensitivity is how many decibels the speakers produce with 1 watt of power at 1 meter’s distance from the speaker. A more sensitive speaker requires less amplification to reach the same volume level.

Keep the following factors in mind when deciding how much receiver power you need:

  • Consider the size of your home theater and how loudly you plan on playing your movies and music. If you want to create permanent hearing loss or have a room the size of the Taj Mahal, you might need a receiver that can pump out 150 watts per channel.

  • If you have relatively sensitive speakers and a moderately sized home theater, and you don’t plan on testing the thickness of your window glass with really loud music, a receiver with 70 watts per channel (or less) might do the trick.

  • In general, receivers with about 100 watts per channel (accurately measured) are more than powerful enough in just about any home theater.

Amplifiers (whether separate or in a receiver) make their power by using transistors. In the old days, amplifiers used vacuum tubes — and some really expensive high-end amps still use tubes because some audio enthusiasts prefer their sound.

Inexpensive receivers use an IC (integrated circuit), which provides the power-generating transistors for several audio channels on a single chip. Better receivers have discrete amplifier output transistors — separate transistors for each channel. Typically, you get more power and better sound from a discrete design.