ESX QS-TWO-BT

The ESX QS-TWO-BT combines the extremely compact dimensions of the well-known QS-TWO power amplifier with a built-in Bluetooth 5.0 receiver. This makes the amplifier particularly well-suited for vehicles where modern Bluetooth audio playback needs to be retrofitted without having to replace the existing car stereo.

With dimensions of just 90 x 70 x 35 mm, the power amplifier can be installed even in very tight spaces, such as behind the car stereo or inside the dashboard. Despite its compact design, it delivers up to 2 x 95 watts RMS into 2 ohms or 190 watts RMS in bridged mode into 4 ohms.

The built-in Bluetooth receiver allows for direct wireless music playback from a smartphone or other Bluetooth device. The Bluetooth level can be adjusted to -3 dB, 0 dB, or +3 dB using a jumper, allowing the volume of the Bluetooth signal to be better matched to other sources.

High-level inputs, including the EPS® fault protection system, are available for connecting to factory-installed car stereos. This system is designed to prevent modern OEM stereos from generating error messages due to a perceived lack of speaker load. In addition, the power amplifier features an automatic power-on function and is suitable for vehicles with a start-stop system.

Thanks to its switchable crossover, the QS-TWO-BT can be operated either as a high-pass or low-pass amplifier with a crossover frequency of 80 Hz. According to ESX, the frequency range extends up to 60 kHz, making the amplifier suitable for high-resolution audio signals as well.

Technical Specifications

• Model: ESX Quantum QS-TWO-BT
• Amplifier Type: 2-Channel Nano Digital Amplifier
• Amplifier Technology: Class D
• Number of channels: 2
• Built-in Bluetooth receiver: yes
• Bluetooth version: Bluetooth 5.0
• Bluetooth Level Adjustment: -3 / 0 / +3 dB
• Output power at 4 Ω: 2 x 52 watts RMS
• Output power at 2 Ω: 2 x 95 watts RMS
• Bridged output power at 4 Ω: 1 x 190 watts RMS
• Permissible speaker impedance in stereo mode: 2–8 Ω
• Frequency range: 10 Hz – 60,000 Hz
• High-pass filter: 80 Hz
• Low-pass filter: 80 Hz
• Filter slope according to the QS series: 12 dB/octave
• Crossover: HPF / FULL / LPF switchable
• Efficiency: up to 90%
• Total Harmonic Distortion plus Noise (THD+N) at 5 W: according to the current product page, <0.005%
• Measured THD+N at 5 W: approx. 0.005%
• Measured THD+N at half power: approx. 0.023%
• Measured signal-to-noise ratio: 94 dB(A)
• Input sensitivity during testing: approx. 0.2–5.0 V
• High-level inputs: yes
• EPS® Fault Protection System: Yes
• Low-level/RCA inputs: Yes, via cable connection
• Stereo RCA output: yes, for example, to connect an active subwoofer
• Auto-Turn-On: Yes
• Automatic Power-On: VOX / DC
• Start-stop capable: yes
• Start-stop operation, according to the test, up to approx.: 6.9 V
• Recommended external fuse rating for the QS platform: 20 A
• Heat sink: solid die-cast aluminum housing
• Dimensions (W x H x L): 90 x 35 x 70 mm
• EISA Award: In-Car Streaming Amplifier 2025–2026