ESX QS-FOUR

The ESX QS-FOUR is an exceptionally compact 4-channel digital amplifier that delivers impressive output power despite its minimal dimensions. Measuring just 90 x 35 x 80 mm, the power amplifier can be integrated into the vehicle almost invisibly—for example, directly behind the car stereo or in the dashboard.

Thanks to modern Class D technology, the QS-FOUR achieves an efficiency of up to 90% and combines high energy efficiency with low heat generation. Each of the four amplifier channels delivers up to 60 watts RMS into 2 ohms, providing a significant increase in power output compared to the built-in amplifiers in conventional car stereos.

To ensure seamless integration into existing vehicle systems, the amplifier features high-level inputs with ESX EPS® (Error Protection System), which can prevent potential error messages from the vehicle diagnostic system. The automatic power-on function and start-stop compatibility further simplify retrofitting.

In addition to the four speaker outputs, the QS-FOUR features a stereo RCA output for connecting additional components, such as an active subwoofer. Switchable high-pass and low-pass filters for the front and rear channels allow for flexible adaptation to different speaker configurations.

Technical Specifications

General Characteristics

• Model: ESX QS-FOUR

• Product Series: QUANTUM QS NANO

• Amplifier Type: 4-Channel Digital Amplifier

• Amplifier Technology: Class D

• Number of channels: 4

• Efficiency: Up to 90%

• Speaker impedance: 2–8 ohms

• Bridge Operation: Possible

• Cooling: Solid cast heat sink

• Start-Stop Compatibility: Yes
  
  

RMS Output Power at 14.4 Volts

• 4 x 35 watts RMS at 4 ohms

• 4 x 45 watts RMS at 3 ohms

• 4 x 60 watts RMS at 2 ohms

• 2 x 120 watts RMS bridged at 4 ohms
  
  

Audio Characteristics

• Frequency range: 10 Hz – 60,000 Hz

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

• Signal-to-noise ratio: 101 dB

• Damping factor: 68

• RCA input sensitivity: 0.19–4.3 volts

• High-level input sensitivity: 0.4–8.3 volts
  
  

Crossover Networks

• High-pass filter (HPF) Front: 80 Hz

• Low-pass filter (LPF) Front: 80 Hz

• High-pass filter (HPF) Rear: 80 Hz

• Low-pass filter (LPF) Rear: 80 Hz

• Filter slope: 12 dB/octave

• Front and rear filters can be switched on and off separately
  
  

Connections and Features

• 4 x RCA low-level inputs (Front L/R, Rear L/R)

• 4 x high-level inputs (Front L/R, Rear L/R)

• 2 x RCA low-level outputs (stereo L/R)

• RCA connectors via cable plugs

• High-level inputs with EPS® (Error Protection System)

• Automatic power-on function: VOX / DC

• Connection option for an active subwoofer via the stereo RCA output
  
  

Power Supply and Dimensions

• Operating voltage: 7.3–16.4 volts DC

• External fuse: 25 amps

• Width: 90 mm

• Height: 35 mm

• Length: 80 mm

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