ESX QS-FOUR-BT

The ESX QS-FOUR-BT is an extremely compact 4-channel Class-D amplifier with a built-in Bluetooth receiver. Measuring just 90 x 35 x 80 mm, this power amplifier is particularly well-suited for installations where space is very limited.

Despite its extremely compact design, the QS-FOUR-BT delivers up to 4 x 60 watts RMS into 2 ohms, making it ideal for boosting the power of factory-installed or aftermarket speaker systems. In bridge mode, up to 2 x 120 watts RMS at 4 ohms is available.

A standout feature is the built-in Bluetooth receiver. This allows music to be streamed directly from a smartphone or other compatible Bluetooth device to the amplifier. This is an especially useful way to add modern streaming capabilities to classic cars, modern classics, or vehicles with older factory-installed radios—without having to replace the original radio.

In addition to RCA inputs, the QS-FOUR-BT features high-level inputs, allowing it to be connected directly to the speaker outputs of many factory-installed radios. The built-in ESX EPS Error Protection System prevents speaker diagnostic error messages in compatible vehicles.

The automatic power-on function can be activated via DC offset or an audio signal. Additionally, switchable high-pass and low-pass filters set to 80 Hz are available for the front and rear channels. A stereo RCA output, for example, allows you to connect an active subwoofer or an additional power amplifier.

Thanks to modern Class D technology, the QS-FOUR-BT achieves a high efficiency of up to 90 percent and combines low power consumption with high output power and a very compact design.

Technical Specifications

• Amplifier Type: 4-Channel Digital Amplifier

• Amplifier Technology: Class D

• Number of channels: 4

• Built-in Bluetooth receiver: Yes

• Bluetooth version: 5.0
  
  

RMS Output Power at 14.4 Volts

• 4 ohms: 4 x 35 watts RMS

• 3 ohms: 4 x 45 watts RMS

• 2 ohms: 4 x 60 watts RMS

• 4 ohms bridged: 2 x 120 watts RMS

• Supported speaker impedance: 2–8 ohms
  
  

Audio Characteristics

• Frequency range: 10 Hz – 60 kHz

• Total Harmonic Distortion (THD) at 5 watts: approx. 0.01%

• Damping factor: 68

• Signal-to-noise ratio: 101 dB

• Suitable for high-resolution audio signals

• Efficiency: up to 90%
  
  

Input sensitivity

• RCA/Low-Level Input: 200 mV – 5.0 V

• High-level input: 450 mV – 11.0 V
  
  

Crossover Networks

• Front/Rear High-Pass Filter: 80 Hz

• Low-pass filter (front/rear): 80 Hz

• Filter slope: 12 dB/octave

• Switchable HPF/LPF for front and rear
  
  

Connections

• 4-channel RCA/low-level input: Front Left / Front Right / Rear Left / Rear Right

• 4-Channel High-Level Input

• High-Level Inputs with the ESX EPS Error Protection System

• Stereo RCA Output

• RCA connectors via cable plugs

• Speaker Connections via Cable Plugs
  
  

Bluetooth

• Built-in Stereo Bluetooth Receiver

• Bluetooth version: 5.0

• Frequency range: approx. 2.402 – 2.480 GHz

• Direct music playback from a smartphone or compatible Bluetooth devices

• Ideal for retrofitting Bluetooth in vehicles with older factory-installed radios
  
  

Automatic Power-On

• Automatic power-on function available

• Activation via audio signal / VOX

• Power-On via DC Offset
  
  

Vehicle Compatibility

• High-level inputs for connecting to factory-installed radios

• EPS Error Protection System to prevent diagnostic error messages in compatible vehicles

• Suitable for upgrading existing OEM audio systems

• Its compact dimensions allow for concealed installation, for example behind the dashboard or trim panels
  
  

Power Supply

• Operating voltage: 7.3 – 16.4 volts

• External fuse: 25 A

• High efficiency with low power consumption
  
  

Dimensions

• Width: 90 mm

• Height: 35 mm

• Length: 80 mm

• Dimensions (W x H x L): 90 x 35 x 80 mm