Bose 402C System Controller User Manual

The Bose 402C System Controller is a professional-grade audio control unit designed for integration with Bose 402 Series loudspeakers. It provides precise tonal shaping, system protection, and input/output management for commercial sound installations. Key features include input level controls, equalization, priority muting, and system status monitoring. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting Devices 7. Operation Modes 8. System Protection 9. Care & Maintenance 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: Main control unit with rack-mount design, front panel controls, rear input/output terminals, status indicators, and protection circuitry.

Feature	Description
Input Level Controls	Adjustable gain for each input channel
3-Band Equalization	Precise bass, midrange, and treble adjustment
Priority Muting	Allows one input to override others (e.g., paging)
Output Limiter	Protects connected loudspeakers from overload
Status Indicators	LEDs for power, signal present, and limit activity
Rack-Mount Design	Standard 19-inch rack width (1U height)
Balanced Inputs/Outputs	XLR and 1/4" TRS connectors for professional audio
System Protection	Thermal and short-circuit protection
Power Requirement	100-240V AC, 50/60Hz universal power supply
Bypass Switch	Defeats processing for direct signal path

Installation

Unpack and inspect contents. Mount in standard 19-inch equipment rack.

Rack mounting: Use provided screws to secure unit in rack.
Connect audio sources: Use balanced XLR or 1/4" TRS cables to INPUT connectors.
Connect to amplifiers: Use OUTPUT connectors to feed power amplifiers.
Connect priority input: Use designated PRIORITY INPUT for paging/microphone.
Plug into AC power using included power cord.

WARNING! Ensure proper ventilation; do not block cooling vents. Use qualified installer for permanent installations.

First-Time Setup

Power on unit; verify status LEDs illuminate.

Set input levels: Adjust INPUT LEVEL controls until SIGNAL LEDs illuminate consistently.
Configure equalization: Set BASS, MID, TREBLE to neutral (12 o'clock position) initially.
Set priority level: Adjust PRIORITY LEVEL control for appropriate override volume.
Test limiters: Play loud program material and verify LIMIT LED activates occasionally.
System calibration: Use test tones to set final equalization for room acoustics.

CAUTION! Always power down system when making connections. Use proper cable strain relief.

Specifications

Dimensions: 19" W x 1.75" H x 8" D (rack mount).
Frequency Response: 20 Hz - 20 kHz, ±1 dB.
Total Harmonic Distortion: <0.05% @ 1 kHz.
Input Impedance: 10 kΩ balanced, 5 kΩ unbalanced.
Output Impedance: 100 Ω balanced.
Maximum Input Level: +20 dBu.
Signal-to-Noise Ratio: >90 dB, unweighted.
Equalization: ±12 dB @ 80 Hz, 1 kHz, 10 kHz.
Power Consumption: 15 watts maximum.
Operating Temperature: 0°C to 40°C (32°F to 104°F).

Controls and Settings

Front Panel: POWER switch, INPUT LEVEL controls, 3-BAND EQ, PRIORITY LEVEL, BYPASS switch, status LEDs.

Rear Panel: Balanced INPUT/OUTPUT connectors, PRIORITY INPUT, AC power inlet, ground lift switch.

Input Controls: Adjust gain for each channel. Equalization: BASS (80 Hz), MID (1 kHz), TREBLE (10 kHz). Priority System: Overrides all other inputs when activated. Output Limiter: Automatically controls peaks to protect speakers. Bypass: Removes all processing for direct signal path. Status Indicators: POWER (green), SIGNAL (yellow), LIMIT (red).

Connecting Devices

Audio Sources: Balanced outputs from mixers, media players. Amplifiers: Inputs to power amplifiers. Priority: Microphone or paging system.

Turn off all equipment before making connections.
Use balanced cables for noise rejection in long runs.
Connect priority input to microphone or paging system output.
Use ground lift switch if hum is present (breaks ground loop).

Tip: Label all cables for easy identification during troubleshooting.

Operation Modes

Supports normal operation, priority override, and bypass modes.

Normal operation: All inputs mixed according to level settings.
Priority activation: When priority input receives signal, other inputs are attenuated by preset amount.
Bypass mode: Engages true hardware bypass for critical listening or system testing.
Limit operation: Output limiter activates automatically during peaks; LIMIT LED illuminates.
Status monitoring: Observe LEDs for proper signal flow and system health.

WARNING! Do not operate with LIMIT LED constantly illuminated; reduce input levels to prevent distortion.

System Protection

Output Limiter: Prevents amplifier clipping and speaker damage. Thermal Protection: Automatically reduces output if overheating detected. Short-Circuit Protection: Current limiting on outputs. Priority Muting: Ensures emergency announcements are always audible.

Care & Maintenance

Unplug before cleaning. Use soft, dry cloth only; avoid liquids. Keep vents clear of dust.

CAUTION! Do not use compressed air directly on controls; may force dust into potentiometers.

Regulatory Information

FCC Part 15: Class A digital device; complies with limits for commercial use. CE marked for European compliance. Copyright © Bose Corporation. All trademarks property of Bose Corporation. For technical support, visit www.bose.com/pro or contact Bose Professional Support at 1-877-230-2637.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No output	Power/connections	Check power cord; verify POWER LED; check input/output connections.
Distorted sound	Overload	Reduce INPUT LEVEL; check if LIMIT LED is constantly lit.
Hum or buzz	Ground loop	Engage ground lift switch; ensure balanced cables are properly wired.
Priority not working	Settings/connections	Check PRIORITY LEVEL setting; verify priority input connection.
One channel silent	Cable/control	Swap cables to isolate issue; check INPUT LEVEL for affected channel.

Reset: Power cycle unit; set all controls to neutral positions.

Service: 1-877-230-2637; www.bose.com/pro