Cambridge Audio Stereo Amplifier 651A User Manual

Integrated amplifier  
User’s manual  
2
azur  
651A  
Your music + our passion  
 
azur 651A  
Important safety instructions  
For your own safety please read the following important safety  
instructions carefully before attempting to connect this unit to the mains  
power supply. They will also enable you to get the best performance from  
and prolong the life of the unit:  
1. Read these instructions.  
2. Keep these instructions.  
3. Heed all warnings.  
The lightning flash with the arrowhead symbol within an equilateral  
triangle is intended to alert the user to the presence of un-insulated  
‘dangerous voltage’ within the product’s enclosure that may be of  
sufficient magnitude to constitute a risk of electric shock to persons.  
4. Follow all instructions.  
The exclamation point within an equilateral triangle is intended to alert  
the user to the presence of important operating and maintenance  
instructions in the service literature relevant to this appliance.  
5. Do not use this apparatus near water.  
6. Clean only with a dry cloth.  
WEEE symbol  
7. Do not block any ventilation openings. Install in accordance with the  
manufacturer's instructions.  
The crossed-out wheeled bin is the European Union symbol for  
indicating separate collection for electrical and electronic  
equipment. This product contains electrical and electronic  
equipment which should be reused, recycled or recovered and  
should not be disposed of with unsorted regular waste. Please return the  
unit or contact the authorised dealer from whom you purchased this  
product for more information.  
8. Do not install near any heat sources such as radiators, heat registers,  
stoves, or other apparatus (including other amplifiers) that produce  
heat.  
9. Do not defeat the safety purpose of the polarized or grounding-type  
plug. A polarized plug has two blades with one wider than the other.  
A grounding-type plug has two blades and a third grounding prong.  
The wide blade or the third prong are provided for your safety. If the  
provided plug does not fit into your outlet, consult an electrician for  
replacement of the obsolete outlet.  
CE mark  
This product complies with European Low Voltage  
(2006/95/EC), Electromagnetic Compatibility (2004/108/EC)  
and Environmentally-friendly design of Energy-related Products  
(2009/125/EC) Directives when used and installed according to this  
instruction manual. For continued compliance only Cambridge Audio  
accessories should be used with this product and servicing must be  
referred to qualified service personnel.  
10. Protect the power cord from being walked on or pinched, particularly  
at plugs, convenience receptacles and the point where they exit from  
the apparatus.  
11. Only use attachments/accessories specified by the manufacturer.  
12. Use with only the cart, stand, tripod, bracket, or table  
specified by the manufacturer, or sold with the apparatus.  
When a cart is used, use caution when moving the cart/  
apparatus combination to avoid injury from tip-over.  
C-Tick mark  
This product meets the Australian Communications Authority’s  
Radio communications and EMC requirements.  
13. Unplug this apparatus during lightning storms or when unused for  
long periods of time.  
Gost-R stamp  
14. Refer all servicing to qualified service personnel. Servicing is required  
when the apparatus has been damaged in any way, such as the  
power-supply cord or plug having been damaged, liquid has been  
spilled or objects have fallen into the apparatus, the apparatus has  
been exposed to rain or moisture, does not operate normally, or has  
been dropped.  
This product meets Russian electronic safety approvals.  
FCC regulations  
NOTE: THE MANUFACTURER IS NOT RESPONSIBLE FOR ANY RADIO OR  
TV INTERFERENCE CAUSED BY UNAUTHORIZED MODIFICATIONS TO THIS  
EQUIPMENT. SUCH MODIFICATIONS COULD VOID THE USER AUTHORITY  
TO OPERATE THE EQUIPMENT.  
WARNING  
This equipment has been tested and found to comply with the  
limits for a Class B digital device, pursuant to Part 15 of the  
FCC Rules. These limits are designed to provide reasonable  
– To reduce the risk of fire or electric shock, do not expose this unit to  
rain or moisture.  
protection against harmful interference in a residential installation. This  
equipment generates, uses and can radiate radio frequency energy and,  
if not installed and used in accordance with the instructions, may cause  
harmful interference to radio communications. However, there is no  
guarantee that interference will not occur in a particular installation.  
– Batteries (battery pack or batteries installed) shall not be exposed to  
excessive heat such as sunshine, fire or the like.  
The unit is of Class 1 construction and must be connected to a mains  
socket outlet with a protective earthing connection.  
If this equipment does cause harmful interference to radio or television  
reception, which can be determined by turning the equipment off and on,  
the user is encouraged to try to correct the interference by one or more  
of the following measures:  
The unit must be installed in a manner that makes disconnection of the  
mains plug from the mains socket outlet (or appliance connector from  
the rear of the unit) possible. Where the mains plug is used as the  
disconnect device, the disconnect device shall remain readily operable.  
Only use the mains cord supplied with this unit.  
– Re-orient or relocate the receiving antenna.  
Please ensure there is ample ventilation. We recommend that you do not  
place the unit in an enclosed space; if you wish to place the unit on a  
shelf, use the top shelf to allow maximum ventilation. Do not put any  
objects on top of this unit. Do not situate it on a rug or other soft surface  
and do not obstruct any air inlets or outlet grilles. Do not cover the  
ventilation grilles with items such as newspapers, tablecloths, curtains,  
etc.  
– Increase the separation between the equipment and receiver.  
– Connect the equipment into an outlet on a circuit different from that to  
which the receiver is connected.  
– Consult the dealer or an experienced radio/TV technician for help.  
This unit must not be used near water or exposed to dripping or splashing  
water or other liquids. No objects filled with liquid, such as vases, shall be  
placed on the unit.  
3
 
Limited warranty  
Cambridge Audio warrants this product to be free from defects in  
materials and workmanship (subject to the terms set forth below).  
Cambridge Audio will repair or replace (at Cambridge Audio's option) this  
product or any defective parts in this product. Warranty periods may vary  
from country to country. If in doubt consult your dealer and ensure that  
you retain proof of purchase.  
Ventilation  
IMPORTANT – The unit will become hot when in use. Do not place anything  
on top of the unit. Do not place in an enclosed area such as a bookcase  
or in a cabinet without sufficient ventilation.  
Ensure that small objects do not fall through any ventilation grille. If this  
happens, switch off immediately, disconnect from the mains supply and  
contact your dealer for advice.  
To obtain warranty service, please contact the Cambridge Audio  
authorised dealer from which you purchased this product. If your dealer  
is not equipped to perform the repair of your Cambridge Audio product,  
it can be returned by your dealer to Cambridge Audio or an authorised  
Cambridge Audio service agent. You will need to ship this product in either  
its original packaging or packaging affording an equal degree of  
protection.  
Positioning  
Choose the installation location carefully. Avoid placing it in direct sunlight  
or close to a source of heat. No naked flame sources, such as lighted  
candles, should be placed on the unit. Also avoid locations subject to  
vibration and excessive dust, cold or moisture. The unit can be used in a  
moderate climate.  
Proof of purchase in the form of a bill of sale or receipted invoice, which  
is evidence that this product is within the warranty period, must be  
presented to obtain warranty service.  
This unit must be installed on a sturdy, level surface. Do not place in a  
sealed area such as a bookcase or in a cabinet. Do not place the unit on  
an unstable surface or shelf. The unit may fall, causing serious injury to  
a child or adult as well as serious damage to the product. Do not place  
other equipment on top of the unit.  
This Warranty is invalid if (a) the factory-applied serial number has been  
altered or removed from this product or (b) this product was not  
purchased from a Cambridge Audio authorised dealer. You may call  
Cambridge Audio or your local country Cambridge Audio distributor to  
confirm that you have an unaltered serial number and/or you made a  
purchase from a Cambridge Audio authorised dealer.  
Due to stray magnetic fields, turntables or CRT TVs should not be located  
nearby due to possible interference.  
This Warranty does not cover cosmetic damage or damage due to acts of  
God, accident, misuse, abuse, negligence, commercial use, or  
modification of, or to any part of, the product. This Warranty does not  
cover damage due to improper operation, maintenance or installation, or  
attempted repair by anyone other than Cambridge Audio or a Cambridge  
Audio dealer, or authorised service agent which is authorised to do  
Cambridge Audio warranty work. Any unauthorised repairs will void this  
Warranty. This Warranty does not cover products sold AS IS or WITH ALL  
FAULTS.  
Electronic audio components have a running in period of around a week  
(if used several hours per day). This will allow the new components to  
settle down and the sonic properties will improve over this time.  
Power sources  
The unit should be operated only from the type of power source indicated  
on the marking label. If you are not sure of the type of power-supply to  
your home, consult your product dealer or local power company.  
REPAIRS OR REPLACEMENTS AS PROVIDED UNDER THIS WARRANTY ARE  
THE EXCLUSIVE REMEDY OF THE CONSUMER. CAMBRIDGE AUDIO SHALL  
NOT BE LIABLE FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES FOR  
BREACH OF ANY EXPRESS OR IMPLIED WARRANTY IN THIS PRODUCT.  
EXCEPT TO THE EXTENT PROHIBITED BY LAW, THIS WARRANTY IS  
EXCLUSIVE AND IN LIEU OF ALL OTHER EXPRESS AND IMPLIED  
WARRANTIES WHATSOEVER INCLUDING, BUT NOT LIMITED TO, THE  
WARRANTY OF MERCHANTABILITY AND FITNESS FOR A PRACTICAL  
PURPOSE.  
This unit can be left in Standby mode when not in use and will draw <1W  
in this state. To turn the unit off, switch off at the rear panel. If you do not  
intend to use this unit for a long period of time, unplug it from the mains  
socket.  
Overloading  
Do not overload wall outlets or extension cords as this can result in a risk  
of fire or electric shock. Overloaded AC outlets, extension cords, frayed  
power cords, damaged or cracked wire insulation and broken plugs are  
dangerous. They may result in a shock or fire hazard.  
Some countries and US states do not allow the exclusion or limitation of  
incidental or consequential damages or implied warranties so the above  
exclusions may not apply to you. This Warranty gives you specific legal  
rights, and you may have other statutory rights, which vary from state to  
state or country to country.  
Be sure to insert each power cord securely. To prevent hum and noise, do  
not bundle the interconnect leads with the power cord or speaker leads.  
Cleaning  
For any service, in or out of warranty, please contact your dealer.  
To clean the unit, wipe its case with a dry, lint-free cloth. Do not use any  
cleaning fluids containing alcohol, ammonia or abrasives. Do not spray an  
aerosol at or near the unit.  
Plug-fitting Instructions (UK only)  
Battery disposal  
The cord supplied with this appliance is factory-fitted with a UK mains plug fitted with  
a 5-amp fuse inside. If it is necessary to change the fuse, it is important that a  
5-amp fuse is used. If the plug needs to be changed because it is not suitable for  
your socket, or becomes damaged, it should be cut off and an appropriate plug  
fitted following the wiring instructions below. The plug must then be disposed of  
safely, as insertion into a mains socket is likely to cause an electrical hazard. Should  
it be necessary to fit a 3-pin BS mains plug to the power cord, the wires should be  
fitted as shown in this diagram. The colours of the wires in the mains lead of this  
appliance may not correspond with the coloured markings identifying the terminals  
in your plug. Connect them as follows:  
Please dispose of any discharged batteries according to local  
environmental/electronic waste disposal guidelines.  
Loudspeakers  
Before making any connections to loudspeakers, make sure all power is  
turned off and only use suitable interconnects.  
Servicing  
The wire which is coloured BLUE must be  
connected to the terminal which is marked with  
the letter ‘N’ or coloured BLACK.  
These units are not user serviceable. Never attempt to repair,  
disassemble or reconstruct the unit if there seems to be a problem.  
A serious electric shock could result if this precautionary measure is  
ignored. In the event of a problem or failure, please contact your dealer.  
The wire which is coloured BROWN must be  
connected to the terminal which is marked with  
the letter ‘Lor coloured RED.  
The wire which is coloured GREEN/YELLOW must  
be connected to the terminal which is marked  
with the letter ‘E’ or coloured GREEN.  
If a standard 13-amp (BS 1363) plug is used, a 5-amp fuse must be fitted or, if any  
other type of plug is used, a 5-amp fuse must be fitted, either in the plug or adaptor,  
or on the distribution board.  
4
 
azur 651A  
Rear panel connections  
1
4
5
8
10  
9
3
2
6
7
1
7
Power On/Off  
Pre-Out  
Switches the unit on and off. This switch is a master on/off control that  
completely powers down the unit.  
These outputs can be used to connect to the inputs on an external power  
amplifier or an active subwoofer, etc.  
2
8
AC power socket  
Record Out 1/2  
Once you have completed all connections to the amplifier, plug the  
AC power cable into an appropriate mains socket and turn the unit on.  
Your amplifier is now ready for use.  
These two identical output sockets can be connected to a tape deck or  
to the analogue Record In sockets on a MiniDisc or CD recorder etc.  
9
S1-S5  
3
Loudspeaker terminals  
These inputs are suitable for any 'line level' source equipment such as  
BD/DVD players, DAB or FM/AM tuners, CD players, Netwok Players, iPod  
docks, MP3 players, etc.  
Two sets of loudspeaker terminals are available, A (main loudspeaker  
terminals, top row) and B (secondary switchable loudspeaker terminals,  
bottom row). Connect the wires from your left channel loudspeaker to the  
LEFT positive and negative terminals, and the wires from the right  
channel loudspeaker to the RIGHT positive and negative terminals.  
In each case, the red terminal is the positive output and the black  
terminal is the negative output.  
Note: These inputs are for analogue audio signals only. They should not  
be connected to the digital output of a CD player or any other digital  
device.  
Connecting a turntable  
Care should be taken to ensure no stray strands of wire are shorting  
speaker outputs together. Please ensure that the loudspeaker terminals  
have been tightened adequately to provide a good electrical connection.  
It is possible for the sound quality to be affected if the screw terminals are  
loose.  
If it is desired to connect a turntable without a built-in phono stage, an  
external phono stage such as our 551P or 651P models should be used.  
Contact your Cambridge Audio dealer for more details.  
Note: A very few turntables have built-in phono stages, in which case it is  
not necessary to use a separate phono stage amplifier. If you’re unsure,  
please consult your turntable user manual.  
The use of A and B speakers affords you an easy and inexpensive way to  
create a simple multi-room system.  
10  
Note: When using two pairs of speakers, use speakers with a minimum  
USB interface  
nominal impedance of 8 ohms.  
A USB B type socket is fitted to the 651A to enable the playback of audio  
from a personal computer running either Microsoft Windows or Apple Mac  
OS X operating systems. Some builds of Linux are also suitable.  
4
IR (Infrared) Emitter In  
Allows modulated IR commands from multi-room systems or IR repeater  
systems to be received by the amplifier. Commands received here are not  
looped out of the Control Bus. Refer to the ‘Custom Installation’ section  
for more information.  
Note: Always use a certified cable for USB Audio preferably one that  
displays an official mark. USB cable connections longer than 3m may  
result in inconsistent audio performance.  
5
Control Bus  
Always turn the Volume to minimum, or turn the  
651A off before plugging/unplugging cables to the  
USB input or whilst booting up your PC/Mac.  
In Allows un-modulated commands from multi-room systems or other  
components to be received by the unit.  
Out Loop out for control bus commands to another unit.  
6
Sub-Out  
This output can be used to connect to a subwoofer, if desired.  
5
 
Connections  
Note: Before making any connections, make sure that the 651A is turned  
off.  
Basic connection  
The diagram below shows the basic connection of your amplifier to a  
CD player and a pair of loudspeakers.  
When designing our amplifiers we include features that allow you to  
connect your system in various ways. The inclusion of features such as  
Pre-Out and Speaker B connections mean that you can flexibly configure  
your system depending on your requirements.  
Right  
speaker  
Left  
speaker  
Black  
Red  
Black  
Red  
Red Black Black Red  
Amplifier  
CD player  
Record out connection  
The diagram below shows how to connect the amplifier to a tape recorder  
or other component with a record function. Please note that either of the  
record outputs can be used (as they are both the same signal in parallel).  
Right  
speaker  
Left  
speaker  
Amplifier  
Tape/MD player  
6
 
azur 651A  
Speaker B connections  
The Speaker B connections on the back of the amplifier allow for a second  
set of speakers to be used (i.e. speakers located in another room).  
The Speaker A/B button on the remote control allows the two sets of  
speakers to be toggled on and off. Refer to the Remote Control section of  
this manual for more information on the Speaker A/B operation.  
Set either A or B, or both A and B may be selected for use.  
Note: When using two pairs of speakers, use speakers with a minimum  
nominal impedance of 8 ohms each.  
Speaker A  
Main Room  
Amplifier  
Speaker B  
Room Two  
Pre-Out connections  
The Pre-Out sockets are for connecting to the input sockets of a power  
amplifier, or active subwoofer. The diagram below shows how to connect  
the amplifier to an active subwoofer via either a mono Sub in or Stereo  
Line In inputs on the subwoofer.  
Right  
speaker  
Left  
speaker  
Amplifier  
Or  
Sub  
In  
Line  
In  
Subwoofer  
7
 
Connections cont.  
The 651A also works with most builds of Linux using the native Audio 1.0  
driver. Because Linux builds vary according to their creator’s choice of  
software components including drivers, it is not possible to guarantee  
operation and Audio drivers may need to be loaded.  
USB audio connections  
The diagram below shows how to connect the amplifier to a personal  
computer via USB connection. Connect a USB ‘B-A’ type lead from the  
651A USB input to one of the USB ports on the PC.  
‘Class drivers’ as they are called for generic support of Audio Class 1.0  
device may be available from the Linux community as we do not supply  
these drivers.  
The 651A is USB 1.1 (Full-speed) USB port compatible and support USB  
Audio 1.0, which works with nearly all common operating systems  
(Windows XP, Vista or 7 and Mac OS X 10.5 or higher) and computer types  
without drivers and allows 16 bit audio at 32kHz, 44.1kHz and 48kHz to  
be received.  
Right  
speaker  
Left  
speaker  
Amplifier  
Personal  
Computer  
Note: Always use a certified cable for USB Audio preferably one that  
displays an official mark. USB cable connections longer than 3m may  
result in inconsistent audio performance.  
Always turn the Volume to minimum, or turn the  
651A off before plugging/unplugging cables to the  
USB input or whilst booting up your PC/Mac.  
8
 
azur 651A  
Front panel controls  
4
5
1
2
3
6
7
8
9
10  
11  
12  
1
8
Standby/On  
Volume  
Switches the unit between Standby mode (indicated by dim power LED)  
and On (indicated by bright power LED). Standby is an eco power mode  
where the power consumption is less than one watt. The unit is designed  
so that it can be left safely in Standby mode when not in use.  
Use to increase or decrease the level of the sound from the outputs of the  
amplifier. This control affects the level of the loudspeaker output, the pre-  
amp output and the headphone output. It does not affect the Rec Out  
connections. It is advisable to turn the Volume control fully anti-clockwise  
before switching the amplifier on.  
2
Phones  
9
Balance  
Allows for the connection of headphones with a ¼" jack plug connector.  
Headphones with an impedance of between 32 and 600 ohms are  
recommended. When the headphones are connected, the output to the  
loudspeakers is switched off (both speakers A and B).  
This control allows you to adjust the relative output levels of the left and  
right channels. In the central position the output from each channel is  
equal. This control only modifies the sound through your loudspeakers  
and the Pre-Out sockets – it does not affect the signals sent through the  
Rec Out connections.  
3
Infrared sensor  
Receives IR commands from the supplied Azur remote control. A clear,  
unobstructed line of sight between the remote control and the sensor is  
required.  
10  
S1/MP3 input  
This source input allows you to connect a portable audio device such as  
an MP3 player, plugged into either the rear panel ‘S1’ Phono/RCA input  
pair or the front panel 3.5mm stereo-jack input (labelled ‘MP3 In’).  
4
Protection  
Press the S1 button on the front panel to select the input, or insert a  
device into the front panel socket which automatically selects the input  
and overrides the rear Phono/RCA sockets.  
LED flashes to indicate activation of CAP5 protection system. Refer to the  
CAP5 section of this manual for more information.  
5
Note: Whilst plugging a device into the front panel automatically selects  
the MP3 input, any other input can still be selected once this has been  
done. As a result you may, if desired, leave a device permanently plugged  
into the front panel.  
Speaker LEDs  
Indicator shows the speaker terminals that are selected. The speaker  
terminals selected are changed with the remote control.  
6
Direct  
11  
S2-S5 Source inputs  
This control gives the audio signal a more direct path to the power  
amplifier stage of your amplifier, bypassing the bass and treble control  
circuits for the purest possible sound quality.  
Push the appropriate input selection button to select the source  
component that you wish to listen to. The signal selected is also fed to the  
Rec Out sockets so that it may be recorded. The input should not be  
changed whilst recording.  
7
Bass and Treble  
These controls allow subtle adjustments to the tonal balance of the  
sound. In the central position these controls have no effect. They only  
modify the sound through your loudspeakers and the Pre-Out sockets,  
and do not affect the signals sent through the Rec Out connections.  
With well-produced source material and a good system, the tone controls  
are unnecessary and can be switched out by the ‘Direct’ switch. If the  
musical recording is of poor quality or other factors are affecting the  
sound quality, it may be necessary to adjust the tone controls to  
compensate.  
12  
USB  
This source input allows connection of a personal computer via USB.  
9
 
Remote control  
The 651A is supplied with an Azur Navigator remote control that operates  
both this amplifier and Cambridge Audio Azur range CD players. Insert  
the supplied AAA batteries to activate. The functions relevant to the  
amplifier are as follows:  
Play/  
Stop/  
Pause  
Press the relevant button to play, stop or pause the CD.  
Skip  
Right Skip Press to skip forward by one track on the CD.  
Left Skip Press to skip backward by one track on the CD.  
Standby/On  
Switches the amplifier between On  
and Standby mode.  
Scan  
Press and hold to scan within the selected track. Hold down for seven  
seconds to increase scan speed. Press the right button to fast forward,  
the left button to rewind.  
Source  
Cycles through the amplifier’s source  
inputs.  
Info  
Mute  
Used with CDs that support CD-text. In stop mode, press to toggle  
between album name and total time on the display. During playback,  
press to toggle between track name and track time.  
Mutes the audio on the amplifier. The  
mute mode is indicated by the  
source LED flashing. Press again to  
cancel mute.  
Bright  
Note: The speaker outputs, Pre-out  
and headphone outputs will all  
be muted. The Record outputs are  
unaffected.  
Alters the brightness of the display backlight. There are three levels of  
brightness: Bright, Dim and Off.  
,
,
,
Read the ‘Operating Instructions’ section of the Azur CD manual for  
information on the functions of these buttons.  
Speaker A/B  
Toggles the speaker terminals on the  
rear panel to output speaker A only,  
speaker B only, both speakers A and  
B or no speaker output at all. The  
speaker indicators on the front panel  
of the amplifier show which speaker  
terminals are selected.  
Note: these buttons will function only when the display backlight is in  
either ‘Bright’ or ‘Dim’ modes. If it is set to ‘Off’, the functions do not  
respond.  
Note: The ‘no speaker output’ option  
allows the 651A to be used as a  
preamplifier only.  
Apple device compatibility  
The Azur 651AC Navigator remote control can control the basic functions  
of Apple devices such as Apple TV and Apple’s iPod/iPhone/iPad range  
when docked in a Cambridge Audio or Apple dock.  
Volume controls  
Increases or decreases the volume  
of the amplifier output.  
Press and hold the source button that corresponds to the input that the  
Apple product is connected to whilst also pressing one of the buttons  
below.  
,
,
,
,
,
The six source select buttons are  
used to directly select the input  
source to the amplifier.  
The functions are slightly different depending on the Apple product.  
Select  
Play/pause  
Stop or Menu  
The remaining buttons are reserved  
for use with Cambridge Audio Azur  
CD players.  
Press briefly to skip or navigate left or right. Press and hold to  
scan forwards or backwards.  
Used to control volume and/or navigate menus.  
Open/Close  
Opens and closes the disc tray  
Used to navigate menus.  
Numerical track select  
Press the number of the desired  
track. The track will then play  
automatically from the start of the  
track.  
In addition, the Azur remote can be paired with up to six specific Apple  
devices using any of the six source buttons. This can be useful if you have  
more than one Apple product.  
For more information on pairing refer to your Apple device’s instruction  
manual.  
Track select  
To select a track number greater  
than nine, press -/-- followed by the  
track number. Playback of the  
chosen track starts automatically.  
Pairing – To pair with an Apple device, press and hold the required source  
button along with the button for six seconds. Some devices like Apple  
TV have visual indication once pairing is achieved.  
Un-pairing – To un-pair an Apple device, press and hold any of the source  
buttons along with the button for six seconds.  
10  
 
azur 651A  
CAP5: Five-way protection system  
Cambridge Audio has developed a proprietary protection system to  
ensure reliability and long life of its amplifiers. This protection system  
comprises five main protection methods:  
5. Intelligent clipping detection  
Indicator – Volume is nudged down automatically.  
Description – CAP5 has the ability to detect when the amplifier starts to  
clip or overdrive at its output, which can damage loudspeakers and  
degrade the sound. Clipping distortion is caused at high volume levels  
when the output signal briefly goes outside the maximum voltage that  
the amplifier can provide, causing the tops of the signal to flatten off.  
When CAP5 detects clipping, the volume will be automatically nudged  
down until CAP5 detects an undistorted output.  
1. DC detection  
Indicator – Unit has switched off during operation, protection LED  
constantly flashes in single bursts.  
Description – CAP5 offers loudspeaker protection if the output of the  
amplifier goes to a high constant voltage (DC). This is a rare fault, although  
detecting it could just save those expensive loudspeakers.  
The clipping detection is disabled by default. However, to enable the  
clipping detection, hold down the Standby/On button during power up  
(whilst switching on the unit at the rear panel power switch). The unit will  
indicate this by flashing the protection LED for several seconds.  
Remedy – Due to the necessary sensitivity of the DC protection circuit,  
hard clipping of the amplifier may cause DC protection to be triggered.  
If this fault occurs please switch the unit off, power up again and check  
operation with a reduced volume level. If the DC fault occurs again please  
contact your dealer for service.  
2. Over temperature detection  
Indicator – Unit has switched off during operation, protection LED  
constantly flashes in bursts of two.  
Description – CAP5 includes temperature detection which constantly  
monitors the heat generated by the output transistors. If the monitored  
temperature reaches a high level (suitably within the limits of the output  
devices) the amplifier will automatically switch into a fault mode. If the  
loudspeaker impedance is low, the temperature of the amplifier may rise  
faster as the amplifier is working harder. If the amplifier is mounted in a  
cabinet or the ventilation slots are obstructed, the over-temperature  
detection may activate/reactivate after a short listening time.  
Custom installation (C.I.) use  
Remedy – The unit is not damaged, although it should be left for 15  
minutes to cool down before being switched out of Standby.  
The 651A feature a Control Bus input/output that allow un-modulated  
remote control commands (positive logic, TTL level) to be received  
electrically by the unit and looped to another unit if desired. These control  
commands are typically generated by custom installation (multi-room)  
systems or remote IR receiver systems. The Control Bus sockets are  
colour-coded orange.  
3. Overvoltage/overcurrent detection  
Indicator – Unit has switched off during operation, protection LED  
constantly flashes in bursts of three.  
Description – CAP5 offers V/I protection by constantly monitoring the  
output transistors to keep them working inside their Safe Operating  
Area (SOA). The SOA is a set of limits given by the output transistor  
manufacturer to ensure reliability. V/I also protects the amplifier against  
short-circuits on the speaker terminals during use.  
An IR Emitter Input is also provided that allows modulated IR remote  
control commands to be received electrically by the unit. Commands on  
this input operate the unit only and are not looped out demodulated on  
the Control Bus Output.  
Remedy – The amplifier is being used outside its performance envelope.  
Reduce the volume. Also check to see if there is a short- or partial short-  
circuit between the loudspeaker terminals.  
In addition the units feature 'direct' IR/Control codes as well as toggle  
codes for some of their features to simplify programming custom  
installation systems. Special direct On/Off and Mute commands can be  
accessed on the supplied remote control for teaching into C.I. systems  
as follows:  
Note: If the indication remains the same and multiple loudspeakers are  
being used on each loudspeaker output, then please remove a pair and  
retry. If too many loudspeakers are connected to any amplifier, causing  
the load resistance to drop too low, the amplifier will be overdriven. CAP5  
will detect this situation. If the indication remains the same with only one  
set of loudspeakers connected, there may be a fault with one or both of  
the loudspeakers.  
1. Press and hold the Standby button. The remote first generates its  
standby (toggle) command. Keep holding the button down and after  
12 seconds an amplifier “On” command will be generated. If the  
button is held down for a further 12 seconds, an amplifier “Off”  
command is generated.  
2. Press and hold the Mute button. The remote first generates its  
mute (toggle) command. Keep holding the button down and after  
12 seconds a “Mute On” command will be generated. If the button is  
held down for a further 12 seconds, a “Mute Off” command is  
generated.  
4. Short-circuit detection  
Indicator – As the unit attempts to come out of Standby mode, the  
protection LED flashes in bursts of four.  
Description – During power up from Standby, CAP5 performs a check on  
the loudspeaker terminals to see if a short across the terminals has  
been accidentally introduced. If the resistance measured across the  
loudspeaker terminals is too low, the unit will remain in Standby mode  
until the fault has been removed and power up is re-attempted.  
A full code table for this product is available on the Cambridge Audio  
Remedy – User-related fault. There may be a short-circuit between the  
loudspeaker terminals. Check all loudspeaker connections before  
attempting to switch the unit out of Standby.  
11  
 
Technical specifications  
Troubleshooting  
651A  
Power output  
There is no power  
Ensure the AC power cord is connected securely.  
75 watts (into 8Ω)  
THD (unweighted)  
<0.002% @ 1kHz, 80% of rated power  
<0.03% 20Hz - 20kHz, 80% of rated  
power  
Ensure the plug is fully inserted into the wall socket and is switched on.  
Check the unit is switched on at the rear panel.  
<0.02% 20Hz - 20kHz @ 10W  
Check fuse in the mains plug or adaptor.  
Frequency response (-1dB)  
S/N ratio (ref 1W)  
5Hz - 50kHz  
>92dB (unweighted)  
47kohms  
There is no sound  
Make sure the unit is not in Standby mode.  
Input impedances  
Check that the source component is properly connected.  
Check that your speakers are properly connected.  
Power Amp damping factor  
Max. power consumption  
Standby power consumption  
Bass/Treble controls  
>100  
600W  
Check that the correct speaker outputs are switched on (‘Speaker A/B’  
button on the remote control).  
<1W @ rated mains  
Shelving, ultimate boost/cut  
+/- 7.5dB @ 20Hz and 20kHz  
If source LED is flashing, turn ‘Mute’ off.  
USB input  
USB Audio 1.0  
16 bit 32kHz, 44.1kHz, 48kHz.  
There is no sound on one channel  
Ensure that balance control is in the correct position.  
Dimensions (H x W x D)  
Weight  
120 x 430 x 350mm  
(4.7 x 16.9 x 13.8”)  
Check speaker connections.  
Check interconnects.  
8.4kg (18.5lbs)  
There is a loud buzz or hum  
Check turntable or tone arm for ground and connection lead fault.  
Ensure no interconnects are loose or defective.  
Ensure that your tape deck or turntable is not too close to the amplifier.  
Unable to make tape recordings  
Check that ‘Rec Out’ has been connected correctly.  
There is weak bass or diffused stereo imaging  
Ensure that speakers are not wired out of phase.  
The sound is distorted  
Check that the volume or tone controls are not set too high.  
Protection LED flashing  
See section on CAP5 protection system.  
The remote handset will not function  
Check that the batteries have not expired.  
Ensure that nothing is blocking the remote sensor.  
In the event that the above solutions do not remedy your problem, please  
consult our frequently asked questions (FAQ) section on our website:  
For all servicing, in or out of warranty, please contact your dealer.  
12  
 
azur 651A  
13  
 
Cambridge Audio is a brand of Audio Partnership Plc  
Registered Office: Gallery Court, Hankey Place  
London SE1 4BB, United Kingdom  
Registered in England No. 2953313  
© 2011 Cambridge Audio Ltd  
 

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