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Cambridge Audio 651A Service Manual

Cambridge Audio 651A
70 pages
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Service Manual
651A
Amended Aug 2013 to include APD variant model
Technical specications
Specications
Power output 75 watts (into 8Ω)
THD (unweighted) <0.002% @ 1kHz, 80% of rated power
<0.03% 20Hz - 20kHz, 80% of rated
power <0.02% 20Hz - 20kHz @ 10W
Frequency response (-1dB) 5Hz - 50kHz
S/N ratio (ref 1W) >92dB (unweighted)
Input impedances 47kohms
Power Amp damping factor >100
Max. power consumption 600W
Standby power consumption <0.5W @ rated mains
Bass/Treble controls Shelving, ultimate boost/cut
+/- 7.5dB @ 20Hz and 20kHz
USB input USB Audio 1.0
16 bit 32kHz, 44.1kHz, 48kHz.
USB maximum current rating 500mA
Dimensions (H x W x D) 120 x 430 x 350mm
(4.7 x 16.9 x 13.8”)
Weight 8.4kg (18.5lbs)
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Cambridge Audio 651A Specifications

General IconGeneral
S/N Ratio>92dB (unweighted)
Input Impedance47k ohms
Power Consumption600W
Damping Factor>100
Power Output75W RMS into 8 Ohms
THD (unweighted, 20Hz-20kHz)<0.02%
Frequency Response5Hz - 50kHz (+/-1dB)
Inputs1 x 3.5mm (Front Aux)

Summary

Specifications

Important Safety Instructions

Safety Precautions

Detailed safety instructions for proper and safe operation of the unit.

Compliance and Symbols

Information on regulatory compliance, symbols, and warnings.

Limited Warranty

Front Panel Controls

Rear Panel Connections

Exploded Diagram and Spares

Exploded Diagram

Visual representation of the unit's components for identification.

Spares Table

List of replacement parts with part numbers and descriptions.

Front Panel PCB Information

Schematic

Circuit diagram for the front panel control board.

Layout

Physical layout of components and traces on the front panel PCB.

BOM

Bill of Materials for the front panel control PCB.

Input PCB Information

Schematic

Circuit diagram for the input signal processing board.

Layout

Physical layout of components and traces on the input PCB.

BOM

Bill of Materials for the input signal processing PCB.

Preamp PCB Information

Schematic

Circuit diagram for the pre-amplifier and control circuitry.

Schematic (Continued)

Continuation of the pre-amplifier and control circuitry schematic.

Layout

Physical layout of components and traces on the pre-amplifier PCB.

BOM

Bill of Materials for the pre-amplifier and control PCB.

Protection PCB Information

Schematic

Circuit diagram for the unit's protection circuitry.

Layout

Physical layout of components and traces on the protection PCB.

BOM

Bill of Materials for the protection circuitry PCB.

Speaker PCB Information

Schematic

Circuit diagram for the speaker output stage and protection.

Layout

Physical layout of components and traces on the speaker output PCB.

BOM

Bill of Materials for the speaker output PCB.

Power Amp PCB Information

Schematic (Left Channel)

Circuit diagram for the left channel power amplifier stage.

Schematic (Right Channel)

Circuit diagram for the right channel power amplifier stage.

Schematic (Continued)

Continuation of the power amplifier stage schematic.

Layout

Physical layout of components and traces on the power amplifier PCB.

BOM

Bill of Materials for the power amplifier stage PCB.

Power Supply Schematics

Assembly Details

Wire Harnessing

Instructions for routing and securing internal wires during assembly.

Component Mounting Hardware

Details on transistor mounting hardware and bracket screws.

Mains PCB Information

EU Schematic and BOM

Circuit diagram and BOM for the EU mains input and power filtering.

CU Schematic and BOM

Circuit diagram and BOM for the CU (115V) mains input and power filtering.

Mains PCB Layout

USB Input Audio PCB Information

Schematic

Circuit diagram for the USB audio interface board.

Layout

Physical layout of components and traces on the USB audio PCB.

BOM

Bill of Materials for the USB audio interface PCB.

Integrated Circuit Pin Layouts

Input PCB Pinouts

Pin configuration for ICs used on the Input PCB.

Preamp PCB Pinouts

Pin configuration for ICs used on the Preamp PCB.

Power Amp PCB Pinouts

Pin configuration for ICs used on the Power Amp PCB.

Mains PCB Pinouts

Pin configuration for ICs used on the Mains PCB.

Speaker PCB Pinouts

Pin configuration for ICs used on the Speaker PCB.

Volume and Protection PCB Pinouts

Pin configuration for ICs used on Volume and Protection PCBs.

APD System Information

Part Table and APD Changes

Details on part revisions and modifications for Auto Power Down (APD) functionality.

Input PCB Schematic with APD

Schematic of the Input PCB showing APD integration.

Preamp PCB Schematic with APD

Schematic of the Preamp PCB showing APD integration.

Auto Power Down Trigger Board Schematic

Circuit diagram for the APD trigger signal generation board.

APD Trigger Cable

Specification for the cable connecting APD components.

Specific Circuit Descriptions

Headphone Driver and Pre Out Mute Circuit

Description of the headphone output driver and mute functionality.

VI Protection Schematic

Circuit diagram for the voltage and current protection system.

Switched Mode Power Supply Schematic

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