Sony XM-S400D Review – Sony mini amplifier

Sony XM-S400D

Sony XM-S400D Review – Small power pack style systems like this have literally been all the rage lately. We’ve noticed that people dont always want amplifiers ran all around their vehicles and huge amps mounted in their trunks.

Im excited to see that mobile audio companies like Sony have found a way to create these mini amplifiers and give them awesome sound output. These things can be mounted behind a radio, under a seat or behind a glove box and nobody would know!

Sony XM-S400D Review – Move Over Pioneer, Sony’s Got One Too!

Sony XM-S400D Review
Sony XM-S400D Review

The device is perfect for all your amplification needs, whether it’s the front or the rear speakers it works efficiently for both and can be easily installed with either a factory or an aftermarket system as well.

This is one of the most compact amplifiers from Sony, as it understands that most of the cars don’t have enough space to set-up a big amplifier unit.

This tiny piece of equipment is a powerhouse that will blast both the front and rear speakers.

The entire unit is built around an anodized aluminum extrusion and has stamped steel end panels. The design is not only straightforward but also extremely durable.

The Sony XM-S400D is Class-D 4-channel amplifier which provides an output of 45 Watts per channel RMS and all this at 4 ohms.

Sony XM-S400D Review

You cannot bridge the S400D, but you can efficiently utilize the high and low pass filters which are switchable similar to Pioneers version.

You can also try and run small subwoofers in the rear channels or a set of full-range speakers in the front channels.

The amplifier can easily accept a preamp or even speaker level signals; hence, the entire unit can be hooked up with any factory setting system. 

This amplifier from Sony is equipped with a 120Hz high pass filter for its front channel’s and also a 120Hz low pass filter for the rear ones.

The high pass filter is very good in filtering out any low frequencies from its front channels and eliminate any sort of distortion.

And the low pass filter will quickly eliminate out any external voices and high frequencies its rear channels, primarily when used to drive a subwoofer.

When you are not using full range speakers with its rear channel’s, it is recommended that you turn off the low pass filter, this will improve the quality of the output. Both these crossovers are controlled with separate on/off buttons and have a 12dB per octave slope.

The amplifier consists of an input select switch with which you can set the amp to match an input connection.

When you are connecting the amplifier to one single pair of inputs, the switch should be at “2CH,” and when the same is connected to two pairs of inputs the switch should be at “4CH” whereas all four outputs of the system are fed signal from the 2-channel input only.

The Sony XM-S400D is equipped with High-level sensing technology. Because of which, when you are using the speaker level input, the amplifier can automatically sense the presence of an audio signal on the input and turn on by itself.

Similarly, when no audio signal is detected, it will turn itself off. Because of this feature, you don’t need a remote turn-on wire with this unit.

One more significant feature of this device is the Power/Protect LED present on the left side of the input signal terminal.

This LED will automatically illuminate in case your amplifier is not functioning, and when the LED is flashing quickly, it signifies that the amp has detected a short circuit or power connectors or something else is wrong. And when the same LED is flashing slowly, it means that your amplifier is heating up or is overheated.

Sony XM-S400 Features

For all power and signal connections, the Sony XM-S400D features harnesses only, such as:

Power/speaker output: There is a 40” main harness which consists of connections for power, amplifier turn-on, ground and outputs for both front and rear speakers.

All the speaker outputs follow industry standard color coding only, which makes it easy to install and use. The only thing you should remember is that the power and ground wires should at least be 12-gauge. 

Fuse: the amplifier is equipped with a 15A ATM mini-blade type fuse, which is installed right next to the power/speaker harness plug of the unit.

Input harness: the XM-S400D consists of a 10-pin Molex receptacle which can be used either for speaker level input or line level harness.

The speaker level input, which is 39″ consists of wires to connect the speaker output wires with the head unit. And the line level harness consists of two pairs of female RCAs. Again all wires follow industry standard color coding only. 


  • 45 Watts x 4 channels RMS power output
  • 100 Watts x 4 channels of peak power output
  • 20-20k Hz, best frequency response
  • 83dB signal to noise ratio
  • 14.4v input voltage
  • D-class amplifier
  • Dimensions: 7 1/4” (w) x 1 ½” (h) x 2 ½” (d)
  • Weight: 789g

Package Contains

Sony XM-S400D - Package Contains
Sony XM-S400D – Package Contains
  • 4-channel amplifier
  • 8” RCA input harness
  • Two self-tapping screws, each of ¾” in length
  • Two mounting tabs
  • Operating instructions manual
  • 2 bracket screws, size 1/8” (diameter) x ¼” (length)
  • 39” speaker level input harness
  • 40” power output harness

The Sony XM-S400D is one of the most perfect amplifiers in the category of little or compact amplifiers, which not only adds big power to your system but greatly enhances your overall music experience.

This device offers double the power, especially in comparison to other similar products in the same category and can be easily set up with an aftermarket head unit or a factory set-up.