Also known as a two-channel or stereo amplifier, a dual amplifier is an audio component which can take two monophonic line level inputs and increase their output levels to drive two separate speaker systems. Dual amplifiers have historically been popular as a means of amplifying two-channel stereo signals and remain useful in multichannel sound systems. While the term "dual amplifier" is most common in professional audio circles, two-channel amplification tools remain prevalent in both home and car audio systems.
A dual amplifier, whether referred to as stereo, dual, or dual mono, contains two separate channels of amplification in a single box. This has the benefit of both saving space and reducing cost compared to mono amplifiers, since some components can be shared. On the other hand, it has the potential to introduce compromises in sound quality since having two separate signals mixed together increases the potential for the signals to leak together and cause distortion. In addition, sharing a single power supply between two channels can lead to a power shortage if both channels experience a peak at the same time.
The term "dual amplifier" is extremely common in the professional audio world where it is used to describe public address (PA) amplifiers as well as speaker amplifiers. It is also popular in car audio, where dual amplifiers frequently deliver power to two subwoofers in a system designed to maximize bass response. In home audio applications, the term is rarer, although it frequently is used to refer to dual mono designs which attempt to generate more separation between the two channels than a standard stereo amplifier.
With the ongoing popularity of surround-sound, dual amplifiers face competition from multichannel amplifiers. Home theater enthusiasts can buy amplifiers which contain five or seven channels of amplification in a single, large, component. Although these amplifiers have the advantage of being in a single box, they also have the disadvantage of having multiple channels in the box with the concomitant risk of interference and crosstalk. Audiophiles frequently eschew dual or multichannel amplifiers for monoblock amplifiers which contain just one channel of amplification and create no risk of interference between channels.
Dual amplifier components have an advantage over monoblock amplifiers even in applications where sound quality is the primary concern. Very high-end audio systems use a wiring technique called bi-amping in which a single channel of sound gets split into high and low frequencies. Separate amplifier channels send the high frequency signal to the speaker's tweeter, and the low frequency signal to the speaker's woofer. This theoretically provides better sound quality by both bypassing the speaker's crossover and by keeping the two different signals separate. In these applications, a dual amplifier serves the same role as a mono amplifier in a system that is not bi-amped.