One of the most popular upgrades to a car audio system is to add an amplifier to the speakers. Providing your speakers with extra power allows them to play louder without fear of damage from harmonic distortion. Over the years, Sony has offered many different amplifier solutions that sound good and offer excellent value. Recently, Sony introduced a cool little amp that is a perfect upgrade to a factory or aftermarket radio. In this product spotlight, we are going to look at the Sony XM-S400D Class D four-channel amplifier.

Size and Specifications

Sony has used the industry-reference CEA-2006 Car Amplifier Standard for the power ratings, as well as the signal to noise ratio specification. Sony rates the XM-S400D as being able to produce 45 watts per channel into a 4 ohm load and a signal to noise ratio of -83 dBA when referenced to 1 watt of output into a 4 ohm load. Lastly, the frequency response of the amp is stated to be 20 Hz to 20 kHz with a tolerance of the -3dB to +0.5 dB.

As you can see from the images, the XM-S400D is in the ultra-compact class of amplifiers. The amplifier measures a diminutive 7-1/4 inches long, 1-1/2 inches tall and 2-1/2 inches wide, excluding any wiring. If you are looking for an amplifier that will fit in a dashboard or center console, then the XM-S400D is one of the smallest on the market.

Features and Connections

Sony built the XM-S400 around an anodized aluminum extrusion with stamped-steel end panels. As simple as it is, it is quite handsome. There is a set of quick connect terminals on each end of the amp. On the right side is a connector for power and remote turn-on input wiring, as well as the eight output speaker wires. Built into the connector is a 15 amp fuse to protect the amp. On the left side is a plug that will accept the included four-channel RCA signal input harness or a different plug with eight wires for speaker-level input signal connections. The amplifier features smart turn-on when using the speaker-level input connections, so there is no need to run a remote turn-on wire in this type of installation.

The left side of the amp also has three signal processing switches. Directly adjacent to the input connection plug is an input select switch. Your installer has the choice of using four channels of input, each routed to the four output channels. Alternatively, if the input select switch is set to the 2-channel mode, the left front input signal is fed to both the left front and left rear output. The right front input feeds both right channels.

Sony has included crossovers on each pair of channels. The front channels have an optional high-pass filter, and the rear channels have an optional low-pass filter. Sony specifies the crossover frequency for both filters at 120 Hz with a slope of -12 dB per octave.

There are no sensitivity controls on the XM-S400D. Sony has designed the amp to produce full power when 1 volt of signal is present at the RCA input jacks or when 8 volts of signal is present on the speaker-level inputs.

Installation Design Features

Sony has included a pair of removable mounting tabs with the amplifier. If you need to secure it to a panel, simply insert the tabs into the slots on each end of the amplifier, secure them with the provided hardware and screw down the tabs. With that said, many installations will find this compact amplifier strapped, tied or taped to a factory wiring harness.

To the left of the signal input terminal is a Power/Protect LED. This LED will illuminate when the amp is on and functioning normally. If the LED is flashing quickly, then the amp has detected a short circuit or the speaker-level input or power connectors may not be inserted into the amp completely. If the LED flashes slowly, it means the amplifier has overheated.

Sony XM-S400D – Big Power in a Small Package

If you are looking for a little amp that can add some big power to your system, then it is well worth checking out the Sony XM-S400D. It offers at least double the power that most premium head units can produce, and it will work with either a factory or an aftermarket head unit. Visit your local authorized Sony retailer for more information, pricing or scheduling an installation.

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