If your car audio sound system is not meeting your expectations then maybe your specifications are to blame.  When examining mono and multi-channel amplifiers, there a few specifications that you should pay closer attention to than others.

Multi-Channel Amplifiers

Pioneer GMD9500F
Pioneer GMD9500F 4-Channel Amplifier

2, 3, 4, 5 or more channel amplifiers are usually Class A/B.  The class is determined by the configuration of the circuitry.  Class A/B circuitry leans towards being more inefficient but provides higher sound quality.  This makes them ideal for mid to high frequencies but are sometimes used for subwoofers as well.  They will also run at much cooler temperatures considering the lower wattage applications they are required to be operated in.  If you are considering purchasing a multi-channel amplifier, then the following specifications should be kept in mind to sway your decision:


  • Signal-to-Noise Ratio: This figure refers to the strength of the signal vs. the level of back ground noise.  A high value will indicate a lower background noise and as a result, a better signal.
  • THD (Total Harmonic Distortion): This is the measurement of the harmonic distortion that is present.  It can be explained as the change in the signal as it is being amplified and exactly how much it is changed.  A lower value is desirable and a THD value of less than .10% is inaudible.
  • Channel Separation:  Sometimes referred to as “cross talk” this value indicates the level of interference between channels.  This value is measured in decibels and the higher the value, the greater and more effective the channel separation will be.

Mono-Channel Amplifiers

Rockford Fosgate PBR300X1
Rockford Fosgate PBR300X1 Monoblock Amplifier

Mono-Channel Amplifiers usually are Class D.  These amplifiers are going to be able to obtain lower ohm loads and higher output which makes them ideal for subwoofers. They are more efficient then their class A/B counterparts. In recent years, monoblock amplifiers have become more efficient and with smaller chassis. Features such as signal-to-noise ratio and THD will often be negatively effected. However, these specifications are not as important as others in regards to mono-channel amps. When examining mono amplifiers there a few different specs you should pay a bit more attention to:


  • Damping Factor: Having a high damping factor means there is a high ratio between the nominal load impedance (typically 8W ) and the source impedance of the amplifier.  It is said that the higher this value is, the more cone control is present which results in a better system response and more accurate bass.
  •  Pre-Amp Outputs: Most Mono amps have pre-amp outputs to daisy chain multiple amplifiers together without splitting the pre-outs from your head-unit.
  • Subsonic Filter:Only on mono amplifiers, this filter allows you to block frequencies that are not able to be reproduced by your subwoofer.  This filter is usally variable between 15-50 Hz.

Using an amplifier in the wrong application is bad, mkay.