TOA A-903MK2 30W 8-Channel Modular Mixer/Amplifier

.The TOA A-903MK2 is a professional 30-watt modular mixer amplifier engineered for maximum flexibility and reliability in commercial audio installations. Featuring eight expansion module slots for complete customization with TOA's comprehensive range of plug-in modules, the A-903MK2 adapts to virtually any application—from paging and background music to foreground audio reinforcement and telephone integration.

TOA A-903MK2 Specifications

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TOA A-903MK2 Modular Mixer Amplifier – 30W Customizable Audio Solution

The TOA A-903MK2 is a professional 30-watt modular mixer amplifier engineered for maximum flexibility and reliability in commercial audio installations. Featuring eight expansion module slots for complete customization with TOA's comprehensive range of plug-in modules, the A-903MK2 adapts to virtually any application—from paging and background music to foreground audio reinforcement and telephone integration.

Designed for demanding commercial environments including retail stores, corporate offices, educational facilities, and houses of worship, the A-903MK2 delivers exceptional audio performance with wide frequency response, ultra-low distortion, and superior output regulation. Multiple output configurations (25V, 70V, 8Ω, and direct 4Ω) accommodate diverse speaker installations, while advanced features like dual mute bus for priority paging, remote volume control, and system expansion capabilities ensure professional-grade functionality.

Built on TOA's legendary platform of reliability and backed by a comprehensive 5-year warranty and UL/cUL safety certifications, the A-903MK2 provides a future-proof foundation for installations requiring scalability, customization, and unwavering performance.

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Key Features

• 30W power output – Clean, reliable amplification for small to medium installations
• Eight module slots – Complete customization with TOA's extensive plug-in module library
• Multiple output options – 25V, 70V, 8Ω transformer-isolated, plus direct 4Ω low-impedance
• Modular architecture – Configure inputs, outputs, and features to exact specifications
• Dual mute bus system – Priority paging with automatic background music ducking
• Remote volume control – External control via optional volume attenuators
• Pre-Out/Power-In jacks – Insert external signal processors or graphic equalizers
• Bridge In/Out connections – Link multiple units for expanded system capacity
• Music On Hold (MOH) output – Direct telephone system integration
• Wide frequency response – 50 Hz to 15 kHz for natural sound reproduction
• Ultra-low distortion – <1% THD at rated output for clean, accurate audio
• Excellent output regulation – Maintains consistent levels across varying loads
• Transformer-isolated outputs – Eliminates ground loops and noise issues
• UL and cUL listed – Meets North American safety standards
• 5-year warranty – TOA's industry-leading reliability assurance
• Professional construction – Heavy-duty steel chassis for long-term durability
• Proven TOA quality – Decades of commercial audio excellence

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Specifications

Power Output

• Rated Power: 30W
• Output Configurations:
  • 25V constant voltage (transformer-isolated)
  • 70V constant voltage (transformer-isolated)
  • 8Ω low impedance (transformer-isolated)
  • 4Ω direct low impedance
• THD: <1% at rated output (1 kHz)
• Frequency Response: 50 Hz – 15 kHz (±3 dB)
• Output Regulation: Excellent (minimal voltage drop under load)

Module Slots

• Total Slots: 8 expansion slots
• Compatible Modules: All TOA M-01 series plug-in modules
• Hot-Swappable: No (power off for module changes recommended)
• Module Types Supported:
  • Input modules (MIC, LINE, telephone)
  • Output modules (zone, MOH)
  • Control modules (mute, remote)
  • Interface modules (contact closure, relay)

Inputs (Via Plug-in Modules) Configuration depends on installed modules. Common options include:

• Microphone Inputs:
  • Balanced XLR or ¼" via M-01F module
  • Sensitivity: -60 dBV (1 mV) typical
  • Impedance: 600Ω balanced
  • Phantom power available (module-dependent)
• Line Inputs:
  • Unbalanced RCA or balanced via modules
  • Sensitivity: -10 dBV to +4 dBV (module-dependent)
  • Impedance: 10kΩ typical
• Telephone/Paging Inputs:
  • Via specialized paging modules
  • Auto-mute and priority control

Outputs

• Primary Speaker Outputs:
  • Screw terminals for 25V, 70V, 8Ω, 4Ω
  • Multiple taps for system flexibility
• Music On Hold (MOH) Output:
  • RCA jack (600Ω output impedance)
  • Level: -10 dBV nominal
• Pre-Out Jack:
  • RCA unbalanced output
  • For connection to external processors
• Bridge Out:
  • For system expansion to additional amplifiers

Control & Features

• Mute Bus:
  • Dual mute bus (Mute Bus 1 and 2)
  • Priority paging with automatic ducking
  • Activated via plug-in modules or external control
• Remote Volume Control:
  • Connection for TOA attenuators (AT-series)
  • Supports multiple remote locations
• Power-In Jack:
  • Returns processed signal from Pre-Out
  • Enables insertion of external EQ or processors
• Bridge In/Out:
  • Links multiple A-903MK2 units
  • Expands system capacity
  • Maintains synchronized muting and control

Front Panel

• Master volume control (rotary knob)
• Power ON/OFF switch with LED indicator
• Output level meter (LED or analog, model-dependent)
• Module slot access (behind removable panel)

Rear Panel

• Speaker output terminals (25V, 70V, 8Ω, 4Ω)
• Eight module slots (numbered for easy identification)
• Pre-Out/Power-In RCA jacks
• Bridge In/Out connections
• MOH output (RCA)
• Remote volume control connector
• Mute bus connections
• AC power input

Protection Features

• Output short circuit protection
• Thermal protection with auto shutdown
• Overload protection
• Transformer isolation (eliminates ground loops)
• Soft-start circuitry

Physical

• Dimensions: 16.9" × 4.1" × 12.6" (430 × 105 × 320 mm)
• Weight: Approx. 19.8 lbs (9 kg) without modules
• Mounting: Desktop/shelf mount or optional rack ears
• Construction: Heavy-duty steel chassis with ventilated design
• Finish: Black textured paint
• Cooling: Natural convection with ventilation slots

Power Requirements

• AC Input: 120V AC, 60 Hz (North American model)
• Power Consumption: 70W maximum
• Standby Power: Minimal (when in standby via mute control)

Operating Conditions

• Operating Temperature: 32°F – 104°F (0°C – 40°C)
• Storage Temperature: -4°F – 122°F (-20°C – 50°C)
• Humidity: 90% RH or less (non-condensing)

Certifications & Warranty

• UL Listed (USA)
• cUL Listed (Canada)
• FCC Part 15 Class A compliant
• 5-year manufacturer warranty

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Mute Bus Priority System

The A-903MK2's dual mute bus enables sophisticated priority control:

Mute Bus 1 (High Priority):

• Emergency paging
• Telephone paging
• Critical announcements
• Automatically mutes Bus 2 and background music

Mute Bus 2 (Medium Priority):

• General paging
• Staff announcements
• Automatically mutes background music only

Priority Hierarchy:

1. Mute Bus 1 (highest priority)
2. Mute Bus 2 (medium priority)
3. Background music (lowest priority)

Applications:

• Emergency notifications override all other audio
• Telephone paging interrupts background music
• Multiple priority levels for complex facilities

System Expansion with Bridge In/Out

Link multiple A-903MK2 units for expanded capacity:

Benefits:

• Increase total power output
• Add more zones while maintaining centralized control
• Distribute amplification closer to speakers (reduces line loss)
• Maintain synchronized muting across all units

Configuration:

• Connect Bridge Out from master unit to Bridge In of slave unit(s)
• All units respond to mute bus triggers simultaneously
• Master controls overall system operation
• Up to 4-6 units can typically be bridged (verify with TOA)

Applications

• Retail & Commercial:
  • Stores and shopping centers
  • Restaurants and cafés
  • Hotels and lobbies
  • Banks and credit unions
• Corporate & Office:
  • Office buildings and complexes
  • Conference rooms
  • Reception areas
  • Manufacturing facilities
• Education:
  • Schools and universities
  • Classrooms and hallways
  • Cafeterias and gymnasiums
  • Administrative offices
• Worship:
  • Churches and temples
  • Fellowship halls
  • Overflow and cry rooms
  • Multi-building campuses
• Healthcare:
  • Hospitals and clinics
  • Waiting rooms
  • Common areas
  • Nurse call integration
• Other Applications:
  • Museums and galleries
  • Transportation facilities
  • Government buildings
  • Background music systems
  • Paging and announcement systems

Why Choose the A-903MK2?

• Ultimate flexibility – Eight module slots allow precise customization
• Future-proof design – Add or change modules as needs evolve
• Cost-effective – Pay only for the modules you need now
• Proven reliability – TOA's decades of commercial audio excellence
• Industry-standard compatibility – Works with existing TOA modules
• Professional features – Priority paging, remote control, system expansion
• Long-term support – 5-year warranty and ongoing module availability
• Easy maintenance – Modular design simplifies service and upgrades

What's in the Box

• TOA A-903MK2 modular mixer amplifier (30W)
• AC power cord
• User manual
• Warranty registration card
• Module slot cover plates (if slots are empty)