Tuning Solutions Mercedes Benz MOST-25 Digital Pre-Amp EW-BZMO-V721 V1 Single Output

Eway Tech Tuning Solutions MOST25 Fibre Optic Audio System Interface for Mercedes-Benz (EW-BZMO-V721-V1) with Single Output

Modern Mercedes-Benz vehicles are equipped with sophisticated factory head units (COMAND / Audio 20) that control critical vehicle settings, navigation, ambient lighting, climate displays, and safety chimes. Upgrading the factory sound system used to mean choosing between poor sound quality or sacrificing your vehicle's integrated dashboard features. The Eway Tech EW-BZMO-V721-S solves this completely by allowing you to keep your original dash unit intact while tapping directly into the uncompressed digital audio stream.

A clean, quiet power supply and direct digital signal integration are essential for true hi-fi audio performance. Built around core Microchip and Texas Instruments (TI) processing architectures with Elna audio-grade capacitors, the EW-BZMO-V721-S delivers pure SPDIF optical and coaxial signals directly to your aftermarket DSP or power amplifier without generating switching harshness or distortion.

Key Benefits of Retaining the OEM Head Unit:

• 100% Original Dash Appearance & Functionality: Maintain your Mercedes-Benz factory interior aesthetic, complete dashboard screen displays, steering wheel controls, and central controller dial interaction without installing an aftermarket head unit.
• Pure High-Fidelity Audio Extraction: Instead of tapping into degraded high-level speaker signals, the module extracts pristine, uncompressed digital audio straight from the MOST25 optical bus before any factory equalisation or distortion occurs.
• Full Factory Safety & Alert Retention: Seamlessly preserves essential vehicle safety overlays, including reverse parking sensor chimes, blind-spot warning alerts, Bluetooth hands-free phone calls, and navigation voice prompts.
• Clean Aftermarket DSP/Amplifier Integration: Feeds pristine digital optical or coaxial signals directly into your aftermarket Digital Signal Processors (DSPs) and high-performance amplifiers, giving you full control over your sound stage without modifying factory vehicle coding.

This single-zone interface module extracts raw digital audio directly from the factory optic bus and provides a single set of TOSLINK optical and coaxial SPDIF outputs. Designed for direct installation, it features direct screw terminal wiring on the unit chassis for hardwired power and trigger connections without needing a pre-built loom plug adapter. It delivers clean full-frequency stereo audio directly to your aftermarket DSP or amplifier while fully preserving your factory head unit controls, warning chimes, and reverse parking alerts.

Key Features & System Integration:

• MOST25 Fibre Optic Extraction: Taps directly into the high-speed MOST25 bus to deliver clean, uncompressed digital audio.
• Premium Hardware Architecture: Engineered with Microchip/TI core processing chips and Elna audio capacitors for full-frequency digital fidelity.
• Single-Zone Digital Output Set: Equipped with a single TOSLINK Optical output and single SPDIF Coaxial output for direct digital audio routing to downstream amplifiers or DSPs.
• Direct Screw Terminal Wiring: Integrated screw terminal block directly on the module chassis for secure, hardwired connections without requiring an external wiring loom.
• Status Diagnostic LEDs: Built-in LED indicators for MOST network activity (ACT) and Remote Turn-On (REM-OUT) power state for fast installation troubleshooting.
• Integrated DIP Switch Attenuation: On-board DIP switch configuration allowing precise output gain and media/alarm attenuation tuning.
• Automatic Power Management: Operates directly via fibre optic signal control - following the factory head unit sleep and wake cycles with low-voltage protection, requiring no external ignition (ACC) wiring.
• Full OEM System Retention: Preserves factory steering wheel volume controls, hands-free phone audio, navigation voice cues, and safety reverse parking sensor chime overlays.

Vehicle Compatibility (if in any doubt, please check with us):

Technical Specifications:

• Model Part Number: EW-BZMO-V721-S
• Core Processing: Microchip / Texas Instruments (TI) with Elna audio capacitors
• Input Signal: MOST25 automotive fibre optic bus
• Output Signals: 1x TOSLINK Fibre Optic / 1x SPDIF Coaxial (Full Frequency Output)
• Wiring Interface: Direct screw terminals integrated into chassis (No external loom plug required)
• Operating Voltage: DC 10V to 18V (Fibre signal control, no ACC ignition wire needed)
• Protection: Low-voltage protection with automatic sleep cycle synchronisation

Kit Includes:

• 1x Eway Tech EW-BZMO-V721-S MOST25 Converter Module (Single Output / Terminal Block)
• 1x MOST fibre optic patch cable and inline connector coupler

Installation, Wiring & Panel Connection Guide:

1. Direct Screw Terminal Connections

• +12V Terminal: Connect directly to a fused continuous +12V battery power supply source.
• GND Terminal: Connect directly to a clean, solid metal chassis ground wire.
• REM Output Terminal: Remote turn-on trigger output. Connect directly to the remote input of your downstream DSP or power amplifier to control system power-up. Verify activation via the REM-OUT Power Indicator LED.

2. Panel Layout & Port Connections

• MOST Optical Port: Connects into the vehicle's MOST25 fibre optic ring. Verify activity via the ACT/Network Activity LED.
• Digital Optical Output: Single TOSLINK digital optical output for master audio signal to DSP or amplifier.
• Digital Coaxial Output: Single SPDIF digital coaxial output for master audio signal to DSP or amplifier.
• Configuration DIP Switch Bank: Module setup switches.

3. DIP Switch Configuration Setup (Pins 3 & 4 Media/Alarm Volume Attenuation)

Note: You MUST power off the unit before altering DIP switch settings for changes to take effect.

• 0 dB Attenuation: Pin 3 UP / Pin 4 UP
• -5 dB Attenuation: Pin 3 DOWN / Pin 4 UP
• -10 dB Attenuation: Pin 3 UP / Pin 4 DOWN
• -15 dB Attenuation: Pin 3 DOWN / Pin 4 DOWN

4. MOST25 Optical Loop Integration

• High-Spec Systems (Benz / Harman Kardon / Bose / Logic7): The high-spec audio interface is natively supported - no additional vehicle activation or software coding is required.
• Vehicles with OEM Factory Amplifier: Disconnect the factory optical plug from the OEM amplifier (located in the boot or under the seat) and insert it directly into the MOST optical input port on the converter module.
• Vehicles without OEM Factory Amplifier: Connect the supplied MOST optical patch cable into the back of the factory head unit (COMAND system) and route to the converter module.
• Optical Loop Continuity: The MOST network operates in a continuous ring. If removing an OEM factory amplifier entirely, install an optical loop bypass coupler on any disconnected factory fibre connectors to keep the remaining vehicle electronics communicating properly.

5. Initial Settings & Post-Installation Setup

• LED Diagnostic Status Check: Turn the vehicle ignition on and verify module operation:
  • ACT (Network Activity) LED: Confirms active data communication on the MOST optical network ring.
  • REM-OUT (Remote Output) LED: Confirms the remote turn-on trigger is active and supplying power to your aftermarket DSP or amplifiers.
• Factory Head Unit Audio Adjustments: Access the OEM Mercedes audio menu and set Bass, Treble, and Equaliser controls to flat (0) to ensure a clean, uncoloured digital signal is delivered to your aftermarket processors.

Professional Installation Recommended:

Integration with fibre optic vehicle networks requires careful handling of optical cables, proper DC power connections, and correct DIP switch setup. Professional installation by a qualified car audio technician is recommended to prevent damage to the optical loop or vehicle electrical system.

Technical & Safety Disclaimer: Always disconnect vehicle power before altering wiring or changing DIP switch configurations. Verify signal routing, battery polarity, and terminal connections prior to powering up the system. Incorrect wiring or forced bends in fibre optic cables can lead to system malfunction or loss of network communication.