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ESX Quantum QS-FOUR-BT 4-Channel Class D Nano Digital Amplifier with Bluetooth Receiver

The ESX Quantum QS-FOUR-BT is an ultra-compact 4-channel Class D "nano" amplifier featuring an integrated Bluetooth 5.0 receiver dedicated to high-definition wireless music streaming. Measuring just 90 x 35 x 80 mm, this high-efficiency micro amplifier delivers up to 4 x 60 Watts RMS into 2 Ohms, providing substantial power to upgrade entire vehicle speaker systems without requiring an aftermarket head unit or extensive modifications.

Featuring automatic signal detection, the amplifier prioritises incoming Bluetooth audio streaming, fading out the main wired input whenever music begins playing from your phone. When playback stops, the system automatically switches back to the primary audio source. An external screw-on Bluetooth antenna is supplied to ensure stable wireless coverage when installed behind the dashboard or in hidden compartments.

Features:

Ultra-compact 4-channel Class D design with heavy cast iron heat sink for optimal thermal management.
Integrated Bluetooth V5.0 receiver dedicated to high-definition wireless audio and music streaming (A2DP). Note: Audio streaming only; does not support hands-free phone calls.
Automatic source switching that prioritises Bluetooth audio over wired inputs.
Hardware BT GAIN jumper (-3 dB / 0 dB / +3 dB) and dedicated BT Rear Level rotary control for fine-tuning sound balance.
High-level inputs with EPS (Error Protection System) to prevent factory audio diagnostic errors.
Automatic power-on function via DC offset or VOX (signal detection).
Start/stop vehicle electrical system compatible (7.3V to 16.4V operating range).
Independent Front and Rear crossover switches for High Pass (HP), Low Pass (LP), or Full Range @ 80 Hz (12 dB/octave).
RCA low-level inputs (Front/Rear) and stereo RCA line outputs for active subwoofer connection.
External Bluetooth antenna included for optimum signal range.

Specifications:

General

Power Output (RMS @ 13.8 V): 4 x 35 Watts @ 4 Ohms
Power Output (RMS @ 13.8 V): 4 x 45 Watts @ 3 Ohms
Power Output (RMS @ 13.8 V): 4 x 60 Watts @ 2 Ohms
Bridged Output (RMS @ 13.8 V): 2 x 120 Watts @ 4 Ohms
Loudspeaker Impedance: 2 - 8 Ohms per channel / 4 - 8 Ohms bridged
Input Sensitivity: 220 mV - 5.4 V
Bluetooth Profile: A2DP (wireless music streaming only, no hands-free phone calling)
Frequency Response: 10 Hz - 60 kHz
Total Harmonic Distortion (THD+N @ 5W/RMS): less than 0.007%
Damping Factor: 140
Signal-to-Noise Ratio: 101 dB
Efficiency: up to 90%
Operating Voltage: 7.1V - 15.9V DC
External Fuse: 25 A
Dimensions: 90 x 35 x 80 mm

Connections & Controls

Low-Level Inputs: Front and Rear RCA via harness connector (220 mV - 5.4 V)
High-Level Inputs: Front and Rear speaker wire harness with EPS - Error Protection System
Low-Level Outputs: Stereo RCA via harness connector for subwoofer expansion
Speaker Impedance Range: 2 - 8 Ohms per channel / 4 - 8 Ohms bridged
Front & Rear Crossovers: Switchable FULL / HP 80 Hz / LP 80 Hz
Auto Turn-On Switch: OFF / VOX / DC

Supplied Parts

ESX QS-FOUR-BT main amplifier unit
Power input wiring harness with inline fuse holder and 25 A fuse
Speaker output harness (8-pin connector)
Low-level RCA input/output harness (12-pin connector)
High-level input wire harness with EPS
Screw-on Bluetooth antenna
Mounting screws and owner's manual