Brax MX4 PRO – 4-channel Class AB high-end amplifier with digital inputs
Version: Silver
The MATRIX MX4 PRO is a 4-channel Class AB amplifier from the BRAX high-end range, made in Germany. Each unit is built to order and its serial number is recorded in a database. It delivers 300 W RMS per channel regardless of whether the load is 4, 2 or 1 ohm, and integrates into digital BRAX systems via SPDIF inputs.
Its power supply provides separate, stabilised voltages for each channel pair, using ultra-low-ESR electrolytic capacitors made specially for Audiotec Fischer and encapsulated toroidal transformers supplying more than 1,800 W. The power transistors are hand-selected for every amplifier with in-house developed measuring equipment, and the revised PCB has four heavy copper layers. With the BRAX DSP, the DiSAC system sets the volume in the analog domain just before the output stages.
Key Features
- Impedance-independent power: 4 × 300 W RMS into 4, 2 and 1 ohm; 2 × 600 W bridged.
- Digital inputs: Two stereo SPDIF inputs, optical and coaxial.
- DiSAC volume control: Volume of the digital inputs controlled via the BRAX DSP.
- 32 hand-selected MOSFETs: High-end output transistors selected for each amplifier.
- Stabilised power supply: Regulated switch-mode supply with separate voltages per channel pair and power supply synchronisation to improve SNR.
- Toroidal transformers: Encapsulated, with high-permeability cores; more than 1,800 W supply output.
- 40,000 µF capacitance: Eightfold-contacted low-ESR capacitors plus a 300 A suppressor choke to smooth peak currents.
- Clean signal path: No coupling capacitors; relay input switching with gold-plated contacts.
- Quad-layer PCB: Four copper layers for higher power and signal flow.
- Damping factor above 1,400: At 4 ohms.
- Speaker protection: High-current power relays.
- Thermal design: Temperature-controlled fan in the bottom plate, heatsink of special aluminium alloy.
Inputs & Outputs
- 4 × RCA inputs, sensitivity 1.0–8.0 V, input impedance 10 kOhm.
- 2 × optical SPDIF (32–96 kHz) and 2 × coaxial SPDIF (32–192 kHz) inputs; Burr-Brown 24-bit D/A conversion.
- 1 × Remote In, BRAX Power Stabilizer connector.
- 4 × speaker outputs.
Power & Amplifier Section
- Class AB; 4 × 300 W RMS at 4 / 2 / 1 ohm, 2 × 600 W RMS bridged at 4 and 2 ohms.
- Frequency response 10 Hz – 80 kHz.
- SNR above 116 dB (A-weighted) on both digital and analog inputs; THD below 0.0005 %.
- Damping factor above 1,400.
- Operating voltage 9–16 V (for max. 5 s down to 6 V), start-stop capable; idle current 8.5 A.
DSP & Sound Tuning
The MX4 PRO has no on-board crossovers or EQ. Its DSP link is DiSAC: the BRAX DSP embeds the volume information in the SPDIF stream, the MX4 PRO decodes it and sets lossless analog volume controllers (PGAs) placed after the D/A converters. Volume can be adjusted with the URC.3 cable remote or the DIRECTOR display remote. Full resolution at low volume is retained provided the source delivers a full-scale signal or has no volume control of its own.
Installation & Connectivity Notes
- Fusing: 6 × 25 A LP-Mini (APS).
- Colour Protection System and BRAX Power Stabilizer connector.
- Operating temperature -40 °C to +70 °C.
- Dimensions (H × W × D): 79 × 360 × 360 mm; net weight 12.0 kg.
- Serial number engraved on a stainless steel plate; hand-signed instruction manual included.
- Available in black and silver.
Technical Specifications
| Output power RMS | |
| – @ 4 Ohms | 4 x 300 Watts |
| – @ 2 Ohms | 4 x 300 Watts |
| – @ 1 Ohm | 4 x 300 Watts |
| – bridged @ 4 Ohms | 2 x 600 Watts |
| – bridged @ 2 Ohms | 2 x 600 Watts |
| Amplifier technology | Class AB |
| Inputs | 4 x Cinch 2 x Optical SPDIF (32 – 96 kHz) 2 x Coaxial SPDIF (32 – 192 kHz) 1 x Remote In |
| Input sensitivity | RCA / Cinch 1.0 – 8.0 Volts |
| Input impedance RCA / Cinch | 10 kOhms |
| Input impedance highlevel | – |
| Outputs | 4 x Speaker output |
| Output voltage RCA / Cinch | – |
| Signal converter for digital input | BurrBrown 24 Bit DA converter |
| Frequency response | 10 Hz – 80 kHz |
| Bass boost | – |
| Highpass | – |
| Lowpass | – |
| Bandpass | – |
| Subsonic | – |
| Phase | – |
| Slope high- / lowpass | – |
| Slope subsonic / lowpass | – |
| Signal-to-noise ratio digital input | > 116 dB (A-weighted) |
| Signal-to-noise ratio analog input | > 116 dB (A-weighted) |
| Distortion (THD) | < 0.0005 % |
| Damping factor | > 1400 |
| Operating voltage | 9 – 16 Volts (max. 5 sec. down to 6 Volts) |
| Idle current | 8.5 A |
| Operating temperature range | -40 °C to +70 °C |
| Fuse | 6 x 25 A LP-Mini-fuse (APS) |
| Additional features | Colour Protection System, BRAX Power Stabilizer connector, Start-Stop capability |
| Dimensions (H x W x D) | 79 x 360 x 360 mm / 3.11 x 14.17 x 14.17″ |
| Net weight | 12.0 kg |
Scope of Delivery
1 x High-End Amplifier BRAX MATRIX MX4 PRO
1 x BRAX MATRIX T-shirt
3 x Allen key
1 x Certificate
1 x Hand-signed instruction manual
