What Is a Mono Amplifier?

By James Clark

In most car and home audio applications, a mono amplifier is used to deliver power to a single channel speaker, such as a subwoofer. The mono amp produces a single power signal which is ideally suited to the low frequency design of a subwoofer. Since a mono amp is more stable in maintaining electrical current resistance when power demands increase (measured in ohms), two subwoofers can be wired together to a single mono amp for efficient performance.


A mono amplifier is a single channel amp designed for low frequency sound reproduction, such as the deep bass produced by a subwoofer.


Since it can transmit only a single audio signal, a mono amp is not suitable for stereo music. Instead, a mono amp can be used to deliver power to a single signal speaker, typically a subwoofer that produces low frequency sounds that can be felt as much as heard.


A mono amplifier is stable to 2 ohms, meaning a mono amp can resist that measurement of electrical current. This enables a mono amp to deliver efficient power (watts) to a pair of subwoofers rated at up to 4 ohms each without the need for a second amplifier. When the speakers are wired in parallel, it is safe to connect a pair of 4 ohm subwoofers without risk to the speakers, while delivering the same power strength to both subs. The mono amp is compatible with any speaker with an ohm rating in multiples of 2, for example, 4,6,8 or 10.


The mono amp is not as electronically sophisticated as a multi-channel amp and costs less money as a result. Since a mono amp can be used as a dedicated power supply for subwoofers, audio enthusiasts can save money by purchasing a less expensive mono amp to drive their subs, while using the power from a multi-channel amp to deliver stereo signals to other speakers. This will producer cleaner, richer sounding music.


A mono amplifier for car use is typically installed under a seat, with a fused power wire running to the car battery, a green wire running to a ground terminal, which is typically nothing more than bare metal on the car chassis or an exposed bolt or screw, and two speaker wires connecting to the subwoofer. The black wire connects to the negative terminals on the sub and the amplifier, and the red wire connects to the positive terminals. The audio signal wire to the amp runs off the wiring harness that connects the stereo.