NAD 906 - User Manual

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Summary

Front and Rear Panel Overview

Front Panel Controls and Indicators

Details the front panel controls and indicators like power button and LED.

Rear Panel Connections and Settings

Identifies rear panel terminals, level adjustments, and other connections.

NAD 906 Specifications

Technical Performance Data

Lists detailed technical specifications including power, distortion, and frequency response.

Wiring Diagram

Amplifier Internal Wiring

Illustrates the electrical connections between different PCBs and components.

Schematic Diagram

Amplifier Circuit Schematics

Provides the detailed circuit schematics for the amplifier modules.

PCB Layout

Component Placement on Circuit Boards

Displays the physical arrangement of components on the main circuit boards.

Amplifier Adjustment Procedures

Idle Current Calibration

Procedure for setting the idle current for amplifier modules.

Final Adjustment and Calibration

Steps to perform after initial idle current adjustments.

Exploded Parts List

Component Breakdown and Part Numbers

Detailed list of all components with part numbers and quantities.

Parts List

Comprehensive Component Inventory

Detailed inventory of all parts, including specifications and quantities.

Packing Diagram

Amplifier Packaging and Contents

Illustrates the components and method of packing the amplifier for shipment.

Notes

Proprietary Information and Usage Restrictions

Contains proprietary information and usage restrictions for the manual.

Summary

Front and Rear Panel Overview

Front Panel Controls and Indicators

Details the front panel controls and indicators like power button and LED.

Rear Panel Connections and Settings

Identifies rear panel terminals, level adjustments, and other connections.

NAD 906 Specifications

Technical Performance Data

Lists detailed technical specifications including power, distortion, and frequency response.

Wiring Diagram

Amplifier Internal Wiring

Illustrates the electrical connections between different PCBs and components.

Schematic Diagram

Amplifier Circuit Schematics

Provides the detailed circuit schematics for the amplifier modules.

PCB Layout

Component Placement on Circuit Boards

Displays the physical arrangement of components on the main circuit boards.

Amplifier Adjustment Procedures

Idle Current Calibration

Procedure for setting the idle current for amplifier modules.

Final Adjustment and Calibration

Steps to perform after initial idle current adjustments.

Exploded Parts List

Component Breakdown and Part Numbers

Detailed list of all components with part numbers and quantities.

Parts List

Comprehensive Component Inventory

Detailed inventory of all parts, including specifications and quantities.

Packing Diagram

Amplifier Packaging and Contents

Illustrates the components and method of packing the amplifier for shipment.

Notes

Proprietary Information and Usage Restrictions

Contains proprietary information and usage restrictions for the manual.

The NAD 906 Multi-Channel Amplifier is a robust audio device designed for delivering high-quality sound across multiple channels. It functions primarily as a power amplifier, capable of driving various speaker configurations with significant power output.

Function Description:

The NAD 906 is a multi-channel power amplifier, meaning it takes a low-level audio signal and amplifies it to a level sufficient to drive loudspeakers. It features six independent channels, which can be used to power multiple speakers in a home theater setup, for multi-room audio, or in a bridged mode for higher power output to fewer speakers. Each channel includes input level adjustment, allowing for fine-tuning of the signal gain. The amplifier also incorporates "Soft Clipping" technology, which is designed to prevent harsh distortion when the amplifier is driven beyond its rated power, providing a more musical and less fatiguing sound experience. Bridging functionality allows two channels to be combined to deliver a single, more powerful output, useful for driving demanding speakers or subwoofers.

Important Technical Specifications:

The NAD 906 boasts impressive specifications, indicating its capability for high-fidelity audio reproduction:

Continuous RMS Power Output (8/4 ohms load, Both channels driven): > 30/35 W. This indicates that each channel can deliver at least 30 watts into an 8-ohm load or 35 watts into a 4-ohm load simultaneously across all active channels without significant distortion.
Continuous RMS Power Output (8 ohms load, BRIDGED mode): > 90 W. When channels are bridged, the amplifier can deliver over 90 watts into an 8-ohm load, demonstrating its flexibility for higher power demands.
Rated Distortion (THD. 20Hz - 20kHz): < 0.04%. A very low Total Harmonic Distortion figure across the audible frequency range signifies excellent audio purity and minimal unwanted artifacts.
Slew Factor: > 50. A high slew factor indicates the amplifier's ability to accurately reproduce fast-changing transient signals without distortion.
Slew Rate: 35V / µSEC. This specification further supports the amplifier's excellent transient response, showing how quickly the output voltage can change.
Damping Factor (ref. 8 ohm, 1kHz): > 100. A high damping factor suggests excellent control over speaker cone movement, leading to tighter bass response and improved overall sound clarity.
Input Impedance: 10k ohm // 220 pf. This ensures compatibility with a wide range of preamplifiers and audio sources.
Input Sensitivity (for 1W output): 185 mV. This indicates the voltage required at the input to produce 1 watt of output power.
Input Sensitivity (for rated power): 1000mV. This is the input voltage needed to achieve the amplifier's full rated power output.
Voltage Gain: 24.5 dB. The amount by which the input signal is amplified.
Frequency Response (-3 dB): < 10 Hz / 100kHz. An extremely wide frequency response, extending well beyond the human hearing range, ensures that all nuances of the audio signal are reproduced.
S/N Ratio (A-weighted): > 100 dB. A very high signal-to-noise ratio means that the amplifier produces very little background noise, resulting in a clean and clear audio output.
S/N Ratio (un-weighted): > 90 dB. Even without A-weighting, the signal-to-noise ratio remains excellent.
THD (ref. 250mW output): < 0.04%. Low distortion even at low power levels.
SMPTE IMP (ref. 250mW output): < 0.04%. Low intermodulation distortion, indicating excellent clarity and detail.
Physical Specifications (Width * Height * Depth): 435 * 108 * 381 mm. These dimensions provide an idea of the unit's size for placement.
Net Weight: 13 kg.
Shipping Weight: 14 kg. The substantial weight suggests robust construction and a powerful internal power supply.

Usage Features:

The NAD 906 is designed for flexible and user-friendly operation:

Front Panel: Features a simple power button and a power LED for basic control and status indication.
Rear Panel Connections: Provides comprehensive connectivity for its multi-channel capabilities. Each pair of channels (CH 1/2, CH 3/4, CH 5/6) has dedicated speaker terminals, input level adjustments, line outputs, and inputs.
Bridging On/Off Switches: Allows users to easily configure channels for higher power output when needed.
Soft Clipping On/Off Switches: Provides the option to engage NAD's Soft Clipping feature, which gently limits the waveform when the amplifier is overdriven, preventing harsh distortion and protecting speakers. This is particularly useful for maintaining sound quality during dynamic peaks.
AC Line Cord: Standard power input.
Multi-Channel Configuration: The six channels can be used independently for surround sound systems (e.g., 5.1 or 6.1 configurations), or in various stereo setups, or bridged for more powerful 3-channel, 4-channel, or even a single high-power mono configuration. The line outputs for each channel pair allow for daisy-chaining to other amplifiers or audio equipment.

Maintenance Features:

The service manual outlines specific adjustment procedures for optimal performance:

Idle Current Adjustment: This critical adjustment ensures that the output transistors are biased correctly, minimizing crossover distortion and maintaining optimal operating temperature. The procedure involves connecting a Digital Multimeter (DMM) across specific test points (P-401/P-403 and P-402/P-404) and adjusting potentiometers (VR-447 and VR-448) to achieve a precise DC voltage reading (5mV +/- 0.5mV) without a load across the output terminals. This process must be repeated for each amplifier module.
Final Adjustment: After initial adjustments, the amplifier should be left powered on for a minimum of 5 minutes to stabilize, and then the idle current adjustments should be re-checked to ensure long-term stability and performance.
Exploded View and Parts List: The manual includes detailed diagrams and lists of all internal components, which are invaluable for technicians performing repairs or component replacements. This facilitates easy identification of parts like transistors, capacitors, resistors, and mechanical components.
PCB Layout and Schematic Diagram: These provide a comprehensive understanding of the amplifier's internal circuitry, component placement, and signal paths, essential for troubleshooting and repair.
Service Contact Information: Provided for professional support and inquiries.

Overall, the NAD 906 Multi-Channel Amplifier is a versatile and high-performance audio component, designed for audiophiles and home theater enthusiasts who demand clean, powerful, and flexible amplification. Its robust design and detailed service documentation ensure both excellent performance and ease of maintenance.