ZESTECH 4CH × 75W DSP Amplifier

BOX03 — User Manual & Specification

1. Product Overview

The BOX03 DSP amplifier is built around an automotive-grade digital amplifier chip, delivering a maximum output of 4CH × 75W into 4Ω speakers. It accepts a DC 9V–16V input and runs on an internally regulated DC 24V rail. It uses a universal 16-pin power harness with a maximum operating current of 10A @ 14.4V, and can be connected in series between the vehicle's multimedia head unit and the factory wiring harness to amplify the head unit's audio output. Bluetooth and optical (SPDIF) audio inputs are also supported.

2. Input Modes & Fast Charging

The BOX03 offers three audio input modes and a USB Type-C port with 27W fast charging (9V/3A output under the PD 3.0 protocol). It powers up in Line Input mode by default, amplifying the audio signal from the head unit. In Line Input mode, volume and EQ control on this unit are disabled — please use the volume and EQ controls on the head unit.

3. Switching Input Modes

Long-press the BOX03 encoder button for 3 seconds to step through the input modes. The modes cycle in the following order, and an English voice prompt announces the selection each time the button is pressed:

1. Line Input (default on power-up) — amplifies the audio signal from the head unit.

2. Optical Input (SPDIF) — supports standard digital audio signals at 96kHz–192kHz.

3. Bluetooth Music — supports Bluetooth V3.2–V5.2.

Long-pressing a third time returns the unit to Line Input mode. Repeat the same action to cycle continuously through the input modes.

4. Sound Presets, EQ & Volume

In Optical Input and Bluetooth Music modes, briefly pressing the encoder button cycles through the sound presets: Classical, Jazz, Heavy, Normal, Pop and Rock. Under the Normal preset, the 10-band EQ is fully customizable: 50Hz, 100Hz, 200Hz, 500Hz, 1kHz, 2kHz, 4kHz, 8kHz, 12kHz and 15kHz, with an adjustment range of ±7dB per band. Turn the encoder clockwise to increase the volume and counterclockwise to decrease it.

5. LED Indicators

Mode LED — Solid on in Bluetooth mode; off in Optical mode; blinking once per second in LINE IN mode.

SYS LED — Solid on when a fault is detected; slow blinking (once per second) during normal operation; lights up for 50ms when the button is pressed.

6. Line Input Specifications

Line Input mode accepts an input impedance of 2Ω–16Ω, an audio input frequency range of 20Hz–20kHz, and a signal level of 0mV to +10V.

7. Output Power

Maximum output power: 75W × 4CH (4Ω speakers); output power at 1% THD: 10W × 4CH (4Ω); output power at 10% THD: 50W × 4CH (4Ω). Power conversion efficiency: ≥90%.

8. Protection Functions

In addition to the above, this product provides comprehensive protection:

● If the input voltage drops below 9V or rises above 16V, the unit shuts down immediately to prevent damage.

● If a speaker or output line is short-circuited or left open, the corresponding channel group stops output, while the unaffected channels continue to operate normally.

● If the internal temperature of the amplifier chip exceeds 100°C, audio output is shut down to protect the product from damage.

● If the product's power supply fails and short-circuits, the 15A fuse blows, protecting the vehicle's power system from being affected.

9. Important Note

In Line Input mode, do not connect the unit directly to the output terminals of a digital amplifier, as this may cause noise or result in no audio output.

10. Specification

4CH Car Audio Power Amplifier

Parameter

Value

Operating voltage

DC 12V (9V–16V)

Operating current

1A–10A (dynamic)

Standby current

≤0.1mA @ 12V

Signal-to-noise ratio

96dB

Channel separation

85dB

Distortion (THD)

≤0.01% @ 1W

Audio frequency range

20Hz–20kHz

Rated output power

4CH × 45W @ 4Ω / 12V

Maximum output power

4CH × 75W @ 4Ω / 14.4V

Speaker output impedance

4–8Ω

Head unit audio input impedance

2–16Ω

Optical input (SPDIF)

Supports standard digital audio signals at 96kHz–192kHz

Bluetooth music

Supports SBC/BLE, V3.2–V5.2

Sound presets (±7dB)

Classical, Jazz, Heavy, Normal, Pop, Rock

EQ bands

50Hz, 100Hz, 200Hz, 500Hz, 1kHz, 2kHz, 4kHz, 8kHz, 12kHz, 15kHz

USB Type-C

27W, up to 9V/3A output under the PD 3.0 charging protocol

Accessories

1 × user manual, 1 × power cable

11. Precautions

● For use only in vehicles with a nominal DC 12V power supply.

● Operating temperature: -20°C to +80°C; relative humidity: -20% to +80%*.

● Speaker impedance must not be lower than 4Ω, otherwise the product may be damaged.

Note: The relative humidity range quoted in the source specification has a negative lower limit, which appears to be a typographical error (the conventional figure would be 20%–80% RH). Please confirm with the engineering team before finalising.