Is it a Waste to Connect an Outboard Amplifier to My Receiver?
Q I’d like to know if it would be a waste to use a power amplifier connected to the preamp outputs of an AV receiver with the same rated power. The AV receiver I have in mind is the Denon AVR-3313CI.—Morris Barber / via e-mail
A It depends on the power amp you plan to connect to the receiver. Power amp specs rarely tell a complete story; just because one amp is rated to deliver 125 watts per channel (WPC) doesn’t mean its performance will equal that of another amp rated to deliver the same output. You have to look at what’s behind the specs. The Denon you cite, for example, has a rated power output of 125 watts into 8 ohms, 20 hertz to 20 kilohertz bandwidth, at 0.08 percent THD (total harmonic distortion). And while Denon’s measurement accounts for the full audio range—a more rigorous test than just measuring at 1 kHz—the AVR-3313CI’s spec sheet indicates that it’s for two-channel output.
For Sound &Vision’s AV receiver and amplifier tests, five- and seven-channel continuous-power measurements into an 8-ohm load are also performed. And though we didn’t test the AVR-313CI, we did review a step-down model from the same line, the AVR-2313CI. In that example, the receiver exceeded its 105-watt (8 ohms) power rating for two channels driven continuously but came in below that on five- and seven-channel tests, an outcome that’s likely to be similar for the AVR-3313CI. That said, reduced power on all-channels-driven tests is fairly common for AV receivers—something that ultimately isn’t a huge deal since movie soundtracks rarely demand full power on more than a momentary basis, especially in the surround channels.
To wrap up, using an external power amplifier with the same rated power as the Denon AVR-3313CI wouldn’t necessarily be a waste—as long as its measured perfomance bests that of the receiver’s own built-in amps. (And also if your speakers and room require that much power, which is a different kettle of fish entirely.)