ESX QUANTUM QS-FOUR-BT – ultra-compact 4-channel Class-D amplifier with integrated Bluetooth 5.0

The ESX QS-FOUR-BT is a powerful 4-channel nano amplifier for particularly space-saving car hi-fi installations. With dimensions of just 90 × 35 × 80mm The power amplifier itself can be placed behind panels, in the dashboard or under a seat. Nevertheless, it provides up to 4 × 60 watts RMS at 2 ohms respectively 2 × 120 watts RMS bridged to 4 ohms ready.

This makes the QS-FOUR-BT ideal for upgrading factory speakers, for operating high-quality front and rear systems or for flexible 3-channel configurations with two speakers and a compact subwoofer. The efficient Class D technology achieves an efficiency of up to 90 percent and combines high output power with low power consumption and low heat generation.

The integrated Bluetooth 5.0 receiver allows music to be played directly from a smartphone or tablet. This makes the amplifier particularly interesting for vintage and classic cars whose original radio should be retained for visual reasons. Modern Bluetooth convenience can be added without changing the classic appearance of the vehicle.

Separately switchable high- and low-pass filters are available for the front and rear channels. The fixed crossover frequency of 80 Hz allows for quick adjustment to full-range speakers, smaller component speakers, woofers or a bridged subwoofer. RCA and high-level inputs, EPS support and automatic switching on via audio signal or DC offset also facilitate integration into existing factory and retrofit systems.

Highlights

• Ultra-compact 4-channel Class D digital amplifier
• Built-in Bluetooth 5.0 stereo receiver
• Direct music playback from your smartphone or tablet
• 4 × 35 watts RMS at 4 ohms
• 4 × 45 watts RMS at 3 ohms
• 4 × 60 watts RMS at 2 ohms
• 2 × 120 watts RMS bridged to 4 ohms
• Can be used as a 4, 3 or 2 channel amplifier
• Separate crossovers for front and rear channels
• High pass, full range or low pass selectable
• High and low pass fixed at 80 Hz
• RCA and high-level inputs
• High-level inputs with EPS technology
• Stereo RCA output for active subwoofer or additional amplifier
• Automatic switching on via VOX or DC offset
• Start-stop capable operation
• Frequency range up to 60,000 Hz
• Efficiency of up to 90 percent
• Heavy cast heat sink
• Dimensions of only 90 × 35 × 80 mm

Technical data

Amplifier and area of ​​application

• Device type: 4-channel nano digital amplifier
• Amplifier technology: Class D
• Number of amplifier channels: 4
• Operating modes: 4-channel, 3-channel or 2-channel bridged
• Integrated Bluetooth receiver: yes
• Bluetooth version: Stereo
• Suitable for front speakers, rear speakers, broadband systems, woofers and compact subwoofers
• Operating voltage: 12-volt vehicle electrical system with negative ground
• Minimum impedance in multi-channel operation: 2 ohms per channel
• Minimum impedance in bridged operation: 4 ohms per bridged channel pair

Output power at 14.4 volts

• At 4 ohms: 4 × 35 watts RMS
• At 3 ohms: 4 × 45 watts RMS
• At 2 ohms: 4 × 60 watts RMS
• Bridged to 4 ohms: 2 × 120 watts RMS
• Maximum total RMS power in 2 ohm operation: 240 watts
• Maximum RMS total power in bridge operation: 240 watts
• Permissible loudspeaker impedance in single channel operation: 2 to 8 ohms

Possible system configurations

• Four 4-ohm speakers with 35 watts RMS each
• Four 3-ohm speakers, each with 45 watts RMS
• Four 2-ohm speakers, each with 60 watts RMS
• Two front speakers and two rear speakers
• Two speakers plus a bridged 4 ohm subwoofer
• Two bridged 4 ohm speakers or woofers
• Front and rear system with independently selected filter type
• Impedances below 2 ohms per individual channel are not permitted
• Impedances below 4 ohms per bridged channel pair are not permitted

Bluetooth functions

• Bluetooth receiver: integrated
• Bluetooth version: 5.0
• Transmission: Stereo audio streaming
• Direct playback from smartphone or tablet
• External Bluetooth antenna: included
• Radio frequency range: 2,402 to 2,480 MHz
• Maximum radiated power: 30 dBm
• Suitable for Bluetooth retrofitting in vehicles with original radio
• No separate Bluetooth audio source required

Active crossover – front channels

• Integrated filter section: available
• Operating modes: HP, Full or LP
• High pass filter: 80 Hz
• Low pass filter: 80 Hz
• Slope: 12 dB per octave
• Full range mode: complete frequency range
• High pass mode: to relieve the load on small and medium-sized speakers
• Low pass mode: for woofers or special system configurations
• Crossover frequency: fixed
• Continuous frequency adjustment: not available

Active crossover – rear channels

• Integrated filter section: available
• Operating modes: HP, Full or LP
• High pass filter: 80 Hz
• Low pass filter: 80 Hz
• Slope: 12 dB per octave
• Setting possible independently of the front channels
• Full range operation: possible
• Bandpass operation: not intended
• Subsonic filter: not present
• Bass boost: not available

Low level inputs

• RCA inputs: 4 channels
• Channel assignment: Front left, Front right, Rear left and Rear right
• Connection: via the included cable plug
• Input sensitivity: 200 mV to 5.0 volts
• Separate input sensitivity can be set for front and rear
• Suitable for aftermarket radios, DSPs and other preamp outputs

High-level inputs

• High level inputs: 4 channels
• Channel assignment: Front left, Front right, Rear left and Rear right
• Connection: via the included 12-pin cable connector
• Input sensitivity: 450 mV to 11.0 volts
• EPS Error Protection System: available
• EPS function prevents error messages in many vehicle diagnostic systems
• Direct connection to speaker outputs of a factory radio possible
• Additional high-low converter often not required

Low level outputs

• RCA outputs: 2 channels
• Version: Stereo left and right
• Connection: via cable connector
• Suitable for controlling an active subwoofer
• Suitable for controlling another amplifier
• Allows expansion to a multi-amplifier system

Automatic switching on

• Automatic switch-on function: available
• VOX mode: Switch on via a detected low level signal
• DC mode: Switch on via DC offset at the high level input
• Off mode: Operation via classic remote line
• Classic remote input: available
• VOX intended for RCA input signals
• DC detection provided for high-level input signals
• Automatic switch-off after loss of input signal

Audio characteristics

• Frequency range: 10 Hz to 60,000 Hz
• THD at 5 watts: 0.01 percent
• Signal-to-noise ratio: 101 dB
• Damping factor: 68
• Efficiency: up to 90 percent
• Full-range playback well beyond the audible frequency range
• Efficient signal amplification with low power loss

Power supply

• Operating voltage range: 7.3 to 16.4 volts DC
• Nominal electrical system: 12 volts
• Negative vehicle mass required
• Start-stop capable: yes
• Connections: +12 volts, ground and remote
• Power connection: via removable 3-pin plug
• Make the plus and ground cables have identical cable cross-sections
• Lay the ground cable as short as possible
• Mounting on a clean and electrically conductive ground point required

Hedging

• Internal device fuse: not available
• External device fuse: 25 amps
• 25A fuse included
• Install the device fuse in the positive cable
• Maximum distance between amplifier and device fuse: 30 cm
• Additional fuse required near vehicle battery
• Also design the fuse near the battery with 25 amps
• Maximum distance between battery and fuse: 30 cm

Connections and controls

• Front channel input level controls
• Input level control for rear channels
• Crossover switch for front channels
• Crossover switch for rear channels
• Choice between LP, Full and HP
• Automatic power on switch
• 4-channel RCA input via cable connector
• 4-channel high-level input via cable connector
• Stereo RCA output via cable plug
• Removable speaker output plug
• Removable power connector
• Connection for external Bluetooth antenna

Status display and protection

• Combined Power and Protect LED
• Blue indicator: amplifier ready for operation
• Red indicator: overtemperature or operating error
• Automatic resumption after sufficient cooling
• Over-temperature protection
• Protection in the event of a short circuit at the speaker output
• Protection if speaker impedance is too low
• EPS protection system for OEM integration

Construction and environmental conditions

• Heavy cast heat sink
• Optimized heat dissipation with minimal dimensions
• Permissible humidity: 10 to 90 percent
• Permissible temperature range: −25 to +50 °C
• Requires assembly in a dry and ventilated place
• Protect from moisture, dust, dirt and direct heat
• Do not install in completely enclosed areas without air circulation

Dimensions

• Width: 90mm
• Height: 35mm
• Length: 80mm
• Dimensions: 90 × 35 × 80 mm
• Design: ultra-compact nano amplifier
• Suitable for installation behind panels, in the dashboard or under a seat

Scope of delivery

• 1 × ESX QS-FOUR-BT 4-channel amplifier
• 1 × 3-pin power connector plug
• 1 × 12-pin cable connector for high-level inputs with EPS
• 1 × 12-pin cable connector for RCA inputs and outputs
• 1 × 8-pin speaker output connector
• 1 × Bluetooth antenna
• 1 × external 25A fuse
• 4 × mounting screws
• 1 × User manual