Your music + our passion
User’s manual
Important safety instructions......................................................................3
Limited warranty...........................................................................................4
Front panel controls.....................................................................................6
Remote control.............................................................................................7
Apple device compatibility...........................................................................7
Operating instructions.................................................................................8
Filters......................................................................................................... 12
Custom installation (C.I.) use................................................................... 14
Troubleshooting......................................................................................... 14
Technical specifications............................................................................ 15
Thank you for purchasing the Azur 851C Upsampling Compact Disc
Player / DAC / Digital Preamp. The 8 series range is fundamental to our
commitment to the continual development of the Azur range. We hope
that you will appreciate the results and enjoy many years of listening
pleasure from it. Like all Cambridge Audio products, the 851C adheres
to our three core principles – stunning performance, ease of use and
incredible value.
The 851C incorporates numerous advanced technologies and
features. Key to its abilities is ATF2™ (Adaptive Time Filtering) our
second generation up-sampling process - developed in conjunction
with Anagram Technologies of Switzerland. This process intelligently
interpolates all incoming audio data (such as 16-bit/44.1kHz from CD)
to 24bit/384kHz through the use of a 32-bit Analog Devices Black Fin
DSP (Digital Signal Processor). The ATF2 system applies polynomial
curve fitting interpolation, and incorporates a time domain model that
allows data buffering and re-clocking to almost completely eradicate
digital jitter, helping to ensure the best possible sound quality. Our new
ATF2 noise shaping algorithm now also provides enhanced linearity with
24-bit sources.
Two very high quality Analog Devices AD1955 24-bit DACs (Digital to
Analog Converters) are used in dual differential mode. Each channel
has its own DAC to process information and completely separate and
symmetrical analog filter circuitry is implemented. These allow both
left and right channel circuitry to operate identically, ensuring the
851C delivers fantastic sound-staging and stereo imaging properties.
All filtering from DACs to output is also fully differential in nature. This
fully balanced configuration largely rejects the already very low noise
and distortion products present in the DACs and filters and provides
an unprecedented level of performance. Balanced (XLR) outputs are
fitted as well as summed conventional unbalanced phono/RCA outputs.
Automatic DC servo circuits null all DC offsets allowing no capacitors in
the signal path.
For this new model two 24-bit capable digital inputs are fitted allowing
other digital sources to be brought into the 851C.
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This guide is designed to make installing and using this
product as easy as possible. Information in this document has
been carefully checked for accuracy at the time of printing;
however, Cambridge Audio’s policy is one of continuous
improvement, therefore design and specifications are
subject to change without prior notice.
This document contains proprietary information protected
by copyright. All rights are reserved. No part of this manual
may be reproduced by any mechanical, electronic or other
means, in any form, without prior written permission of the
manufacturer. All trademarks and registered trademarks are
the property of their respective owners.
© Copyright Cambridge Audio Ltd 2012
Cambridge Audio and the Cambridge Audio logo are
trademarks of Cambridge Audio.
Other brands mentioned are trademarks of their respective
owners and are used for reference purposes only.
Also a 24-bit isochronous USB audio interface is provided that enables
the 851C to play audio from a personal computer / laptop. This can
handle up to 24-bit/96kHz content from most Windows, Mac and Linux
builds. In certain circumstances up to 24-bit/192kHz material can
also be supported. See later section on Mac/PC/Linux setups and in
particular our own free Windows driver.
Digital volume and output mute functions are incorporated that enable
the 851C to operate as a combined CD player, DAC and digital preamplifier that can be connected directly to a separate power amplifier
if desired.
In addition to these audiophile features Control Bus Input/Output, IR
Emitter Input and RS232 control are provided to make it easy to integrate
this unit into Custom Installation systems if desired.
A new 8-series casework combines massive structural rigidity with
careful damping and control of acoustic resonance. An Azur Navigator
remote handset is also provided, giving full control of your CD player,
Azur amplifiers and our iD100 digital iPod/iPad/iPhone dock in an
attractive and easy to use handset.
Your 851C can only be as good as the system it is connected to. Please
do not compromise on your amplifier, speakers or cabling. Naturally we
particularly recommend amplification from the Cambridge Audio Azur
range, and in particular the 851A Integrated Amplifier which has been
designed to the same exacting standards as the 851C. Your dealer can
also supply excellent quality Cambridge Audio interconnects to ensure
your system realises its full potential.
Thanks for taking the time to read this manual; we do recommend you
keep it for future reference.
Matthew Bramble
Cambridge Audio Technical Director
and the 851C design team
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.
4. Follow all instructions.
5. Do not use this apparatus near water.
6. Clean only with a dry cloth.
7. Do not block any ventilation openings. Install in accordance with the
manufacturer’s instructions.
8. Do not install near any heat sources such as radiators, heat registers,
stoves, or other apparatus (including 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.
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.
13. Unplug this apparatus during lightning storms or when unused for
long periods of time.
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.
– To reduce the risk of fire or electric shock, do not expose this unit to
rain or moisture.
– 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.
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.
Please ensure there is ample ventilation (at least 10cm clearance all
round). 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.
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.
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.
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.
WEEE symbol
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.
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.
C-Tick mark
This product meets the Australian Communications
Authority’s Radio communications and EMC requirements.
Gost-R Mark
This product meets Russian electronic safety approvals.
FCC regulations
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
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.
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:
- Re-orient or relocate the receiving antenna.
- 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.
Limited warranty
IMPORTANT – The unit will become hot when in use. Do not stack
multiple units on top of each other. 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.
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.
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.
Due to stray magnetic fields, turntables or CRT TVs should not be located
nearby due to possible interference.
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.
This unit can be left in Standby mode when not in use and will draw
<0.5W 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.
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.
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
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.
Battery disposal
Batteries may contain substances harmful to the environment. Please
dispose of any discharged batteries with due consideration and in
accordance with local environmental/electronic recycling guidelines.
Before making any connections to loudspeakers, make sure all power is
turned off and only use suitable interconnects.
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.
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.
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
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 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.
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
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.
For any service, in or out of warranty, please contact your dealer.
Plug Fitting Instructions (UK only)
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:
The wire which is coloured BLUE must be
connected to the terminal which is marked
with the letter ‘N’ or coloured BLACK.
The wire which is coloured BROWN must
be connected to the terminal which is
marked with the letter ‘L’ or 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.
Rear panel connections
Power On/Off
Always turn the Volume to minimum, switch to another
input or turn the 851C off before plugging/unplugging
cables to the USB input or whilst booting up/shutting
down your PC/Mac.
Switches the 851C on and off.
Mains Voltage Selector Switch (CU version only)
Switches the 851C mains voltage between 100V and 115V.
Note: For use by Cambridge Audio service personnel only!
Power Socket
Once all other connections are made, connect the supplied power cable
to the 851C power socket and to an appropriate mains socket. The 851C
is now ready for use.
RS232C Interface
The RS232C interface enables external serial control of the 851C in
custom installation applications. A command set is available on the
Cambridge Audio website at The RS232
interface can also be used by Cambridge Audio service personnel for
software updates.
IR (Infra Red) Emitter In
A 3.5mm mini-jack socket that enables modulated IR commands from
multi-room or IR repeater systems to be received by the 851C.
Note: Commands received by the IR Emitter In socket are not looped out
of the Control Bus. Refer to the ‘Custom Installation’ section for more
Control Bus
In – An RCA phono socket that enables un-modulated commands from
multi-rooms systems or other components to be received by the 851C.
Out – An RCA phono socket that provides control bus output commands
for further downstream units.
Digital Outputs
The 851C digital outputs enable a separate DAC (digital to analogue
converter) or digital recording device to be connected. Refer to the
‘Operating instructions’ section for more information.
Three concurrent digital outputs are available. Note these outputs pass
through the currently selected audio source un-processed, i.e. no volume
control or up-sampling is performed on the digital outputs.
Balanced AES/EBU – For external devices incorporating a balanced
(AES/EBU) digital input.
Note: The acronym “AES/EBU” refers to the Audio Engineering Society
and the European Broadcast Union.
Coaxial – To obtain best results, use a high quality 75 ohm digital RCA
interconnect cable (not one designed for normal audio use).
Ground Lift Switch
The Ground Lift Switch enables the USB interface earth to be
disconnected from the 851C chassis earth. Disconnecting (lifting) the
earth can be useful if electronic hum is heard through the speakers
when the USB input is selected. The switch should otherwise be left in
the Ground position.
Digital Inputs 1 & 2
The 851C has three digital inputs in total. Inputs 1 and 2 feature both
S/PDIF co-axial and Toslink optical sockets.
For each input you can use whichever is most convenient, but not both
at the same time.
Coaxial – Use a high quality 75 ohm digital RCA Phono interconnect
cable (not one designed for normal audio use). This input is suitable for
16-24 bit content up to 192kHz.
Toslink Optical – Use a high quality TOSLINK fibre optic interconnect
cable designed specifically for audio use. This input is suitable for 16-24
bit content up to 96kHz (Toslink is not recommened at 192kHz sampling
AES/EBU Digital Input
For sources with a balanced (AES/EBU) digital output. This input is
suitable for 16-24 bit content up to 192kHz.
Unbalanced Audio Output
A conventional RCA phono stereo output for connection to the line-level
inputs of an amplifier. Use a high quality stereo RCA phono interconnect
cable intended for analogue audio signals.
Balanced Audio Output
The 851C features balanced outputs on two XLR sockets. Balanced
outputs provide slightly better audio performance and can reject
cable-borne noise and interference when used with equipment with
balanced inputs.
Note: XLR connectors should be wired as follows:
Pin 1: Ground
Pin 2: Hot (in-phase)
Pin 3: Cold (phase-inverted)
Toslink Optical – Use a high quality TOSLINK fibre optic interconnect
cable designed specifically for audio use.
USB Interface
A USB B type socket is fitted to the 851C 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.
Note: Always use a high quality USB connection cable certified as USB HiSpeed. USB cable connections longer than 3m may result in inconsistent
audio performance.
Front panel controls
Switches the 851C between Standby mode and On. Standby is a low
power mode where the consumption is less than 0.5W. The 851C can be
left in Standby mode when not in use.
Press to enter the 851C's setup menus. Various 851C operating
parameters can be configured. Menus are shown by the 851C display
and accessed through the front panel Select and   buttons. Refer to
the ‘Operating instructions’ section for more information.
A different filter setting is stored for each input and CD playback.
Note: The Filter indicator will flash if Mute is engaged via the remote
Infrared Receiver
Receives IR commands from the Azur handset. A clear unobstructed line
of sight between the remote handset and the receiver is required.
The display shows the currently selected source in addition to a variety
of 851C operational information.
Disc tray
Compact Disc tray. Use the Open/Close button to activate.
Press to Open or Close the disc loading drawer.
Note: Pressing Play when the drawer is open will also close the drawer.
Play/Pause (/)
Press to Play a loaded disc or to Pause playback if it is underway.
Note: Depending on the audio software installed on the host personal
computer, the Play and Pause buttons may also be able to control USB
audio file playback.
Stop 
Stops CD playback.
Skip/Scan ( )
Note: Depending on the audio software installed on the host personal
computer, the Skip/Scan buttons may also be able to control USB
playback from some applications. The scan function is not available
when playing USB audio files.
Display functions
Press to toggle through three alternative digital filter characteristics:
Linear Phase, Minimum Phase or Steep. Alternative digital filters can
offer subtly different sound quality characteristics. The currently selected
filter is displayed by the indicators just above the button.
Press to skip CD tracks. Pressing and holding the button will scan
forwards or backwards through the currently playing CD track. The Skip/
Scan buttons are also used for menu navigation.
Press to select between CD Playback, Digital Input 1, Digital Input 2,
AES/EBU or the USB digital input. Refer to the ‘Operating instructions’
section for more information.
Illuminated during disc playback.
Indicates that disc playback has been paused.
Alpha-numeric characters which display playback information. On
inserting a disc, the CD player will take a few seconds to read the Table
of Contents (TOC) information from the disc. The display will then show
the number of tracks on the CD and the total length of the CD.
If the CD incorporates CD-text, the name of the album will scroll once
(the number of tracks remains stationary throughout). Once playback of
an individual track begins, the track number, total number of tracks and
play-time will be displayed. On a CD containing CD-text, the track name
will scroll once. Pressing the i (Info) button on the remote control will
re-display the CD-text.
Indicates random playback mode.
Illuminated when displaying time remaining on track or disc.
Illuminated when program mode is selected.
Repeat All/Track
Illuminated when ‘Repeat Track’ or ‘Repeat All’ is selected.
The 851C is supplied with an Azur Navigator remote
control handset that duplicates the front panel control
functions and is also able to control Azur series amplifiers.
The supplied AAA batteries must be fitted before the
remore control can be used.
The following buttons are used to control Cambridge
Audio Azur range amplifiers only (such as the matching
851A) or when the 851C has been set to preamp mode
(Digital Volume Enabled).
The Azur handset buttons function as described in the
following paragraphs.
These buttons enable the amplifier volume adjustment for
suitable Cambridge Audio Azur range amplifiers.
Volume Up/Down
Note: If the 851C Digital Volume feature is enabled, the
handset volume buttons will affect the signal output level
from the 851C. Refer to section ‘Operating instructions’
for more information.
Press to toggle through the amplifier inputs.
Switches the 851C between On and Standby modes.
Opens and closes the CD drawer.
Enable direct CD track selection. Press the number of
the desired track to begin playback from the beginning.
To select a track number greater than ten, press the -/-button followed by the track number.
Press to toggle between amplifier volume and balance
control using the volume up
and down
Speaker A/B
Alters the brightness of the 851C display backlight. There
are two brightness levels and an option to switch-off the
Press to switch between the twin speaker outputs on
Cambridge Audio Azur amplifiers with this facility.
Press to mute the output on Cambridge Audio Azur
amplifiers. If the 851C Digital Volume feature is enabled,
this button will mute/unmute the output of the 851C
/ Stop
/ Pause
Press the relevant button to play, stop or pause a CD.
Note: Depending on the audio software installed on the
host personal computer, the Play and Pause buttons may
also be able to control USB audio playback.
Right Skip () – Press once to skip forward by one track
on the CD. Press and hold to skip forwards through tracks.
The Filter indicator will flash when mute is engaged. Press
Mute again to restore output.
Used to select sources on matching CA Azur amplifiers.
Left Skip () – Press once to skip backward by one track
on the CD. Press and hold to skip backwards through
Apple device compatibility
Note: Depending on the audio software installed on the
host personal computer, the Skip buttons may also be
able to control USB audio playback.
The Azur 851AC 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.
Scan Right
Press and hold to search while a CD is playing to search
Scan Left
Press and hold to search while a CD is playing to search
Press to toggle through the five 851C input options. Within
the Setup menus, press to accept the parameter or option
highlighted in the display menu.
Read the ‘Operating Instructions’ section of this manual
for information on the functions of these buttons.
Press to toggle through the three 851C digital filter options.
The functions are slightly different depending on the Apple
Press to enter 851C's setup menus. Various 851C
operating parameters can be configured.
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.
Press to display any additional 851C input signal information available.
Stop or Menu
ress briefly to skip or navigate left or right. Press
and hold to scan forwards or backwards.
Used to control volume and/or navigate menus.
Used to navigate menus.
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
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.
Remote control
Operating instructions
Once all the required input and output connections are made, the 851C
can be switched on using its rear panel Power switch and front panel
or handset Standby/On button. The amplifier to which the 851C is
connected should also be switched on, the appropriate input selected,
and its volume control set at the appropriate level.
Repeating discs and tracks
Either front panel or handset buttons can be used for the majority of the
851C control functions.
To use the 851C as a conventional CD player proceed as described in the
following paragraphs:
Loading and playing CDs
This unit has been designed to play compact discs,
recordable CDs (CD-R) and re-writable CDs (CD-RW)
bearing the identification logo shown here. No other
discs can be used. Any CD-R/CD-RW discs should
contain properly recorded TOC (Table of Contents) information so that
they can be played back. This unit can play only the discs recorded in the
CD-DA format designed for music reproduction. Do not attempt to play a
disc containing other data, such as a CD-ROM for PCs with MP3 or WMA
files, on this unit.
With the 851C switched on and a disc playing, either a specific track or
an entire disc can be set to repeat indefinitely. To repeat a specific track
press the handset Repeat button once while the track is playing. The
851C display will show “Repeat Track”. To repeat an entire disc simply
press the handset Repeat button twice in quick succession. The 851C
display will show “Repeat All”. Track or disc repeat can be cancelled
by a further press of the Repeat button, by pressing the front panel or
handset Stop () button or by opening the disc drawer.
Playing tracks randomly
1. Press the front panel or handset Open/Close button to open the
disc drawer. When the drawer is fully open, place a disc in the drawer
with its label side upwards.
2. To close the disc drawer, press the Open/Close button. When the
drawer, with a correctly loaded disc, is fully closed, the disc table of
contents will be automatically read by the player. The 851C display
will show the number of tracks on the disc and its total playback time.
Pressing the front panel or handset Play () button will also close the
drawer, and start the disc playing.
Note: If the 851C Auto Play setup feature is selected, the disc will always
begin playing as soon as the drawer is closed. Refer to Section 5 – 851C
Setup for more information.
3. If the disc does not begin to play immediately, press the front panel
Play/Pause or handset Play () button to begin playback. To pause
playback temporarily press the front panel Play/Pause or handset
Pause () button. To stop playback press the front panel or handset
Stop () button. While the disc is playing the 851C display will show
the current track name or number and its elapsed time. If the disc is
paused the display will show the elapsed time at which pause was
selected. If the disc is stopped the display will revert to showing the
number of tracks on the disc and its total playback time.
With the 851C switched on and a disc loaded, the tracks can be played
randomly. To select random play simply press the handset Random
button once and then the Play () button. Random play can be cancelled
by a further press of the Random button. The disc will then continue to
play the tracks in the “correct” order following the track that was playing
when random play was cancelled.
Using the Remain function
Note: The 851C should not be left in pause mode for long periods.
4. The disc drawer can be opened at any time by pressing the front panel
or handset Open/Close
button. Remove the disc only after the
drawer has fully opened.
With the 851C switched on and a disc playing, press the handset Remain
button once to display the remaining track time or twice to display the
remaining disc time.
– Do not put anything except a compatible disc into the disc drawer.
Foreign objects may damage the mechanism.
Programming disc play
– Do not force the drawer to open or close by hand.
– Keep the disc drawer closed when the player is not in use.
– If a disc is seriously scratched or dirty the player may not be able to
read or play it.
– Never load more than one disc at a time into the disc drawer.
Playing a specific CD track
With the 851C switched on and a disc loaded, specific tracks can be
selected for playback by pressing one of the front panel or handset
Skip ( ) buttons to step through the tracks on the disc forwards or
backwards. When the desired track is shown on the 851C display, press
the front panel or handset Play () button to begin playback. The disc
will then play from the selected track to the end.
Scanning within tracks
With the 851C switched on and a disc playing, a specific point in a
track can be found by pressing and holding one of the front panel or
handset Scan ( ) buttons to fast-forward or fast-reverse through the
track. When the desired point in the track is reached the button can be
released. The disc will then play from the selected point to the end.
The order in which CD tracks are played can be programmed with a
playlist. Tracks can also be suppressed from a playlist or programmed
to play more than once.
With the 851C switched on and a disc loaded, press the handset Prog
button. The 851C display will show the Program menu. Use the front
panel or handset Skip ( ) buttons to step through the disc to the
track you wish to be the first track in the playlist. Press the handset Play
button to confirm the first track. Repeat this procedure for all the tracks
required in the playlist and then press the front panel or handset Stop
() button to store the programmed playlist. When the playlist is stored,
use the front panel or handset Play (4) button to play the programmed
The front panel or handset Pause (), Skip ( ) and Scan ( )
functions can be used as normal while a programmed playlist is playing.
Press the front panel or handset Stop () button once to stop playback
without deleting the playlist, or press it twice both to stop playback and
delete the playlist.
Using digital inputs
The 851C is fitted with four digital inputs for the connection of external
digital sources. When a digital input is selected, digital audio from
external devices will be up-sampled and delivered to the 851C analogue
outputs. The digital outputs always output the incoming data without
any processing.
The digital input and interface formats are listed in the table below:
When a digital signal is playing through the 851C its display will show
the input stream sample rate and word length (also known as “bit
depth”) along with an indication that the stream is being up-sampled
to 24-bit/384kHz. If no source, or an incompatible data stream, is
connected to a digital input, the display will show UNLOCKED when the
input is selected.
Co-axial or Toslink
Note: Rather than display the exact word length, some sources report
data as either 20 bit maximum (displayed as < = 20) or 24 bit maximum
(displayed as < = 24).
Co-axial or Toslink
XLR balanced
AES/EBU (consumer)
USB Audio
B-type SocketUSB Audio profile 1.0
(default) or 2.0
Digital Input
The 851C digital inputs, and the 851C CD player, are selected
sequentially by pressing the front panel or the handset Select button. In
the case of digital inputs 1, 2 and the AES/EBU input, once the input is
selected, if a compatible data stream is present it will play through the
851C immediately.
The 851C USB input enables the playback of audio files or streamed
programme from Microsoft Windows or Apple Mac OS X personal
computers (and some Linux builds). When connected via USB the
personal computer will identify the 851C as an audio device. Specifying
the 851C in the computer’s audio control panel will enable it to play
audio data either stored locally on the computer or streamed to the
computer via a network or the internet.
USB 'B-A' type lead
Always turn the Volume to minimum, switch to another
input or turn the 851C off before plugging/unplugging
cables to the USB input or whilst booting up/shutting
down your PC/Mac.
Note: Always use a high quality USB connection cable certified as USB HiSpeed. USB cable connections longer than 3m may result in inconsistent
audio performance.
Operating instructions cont.
Advanced USB audio
The 851C is both USB 2.0 (Hi-Speed) and USB 1.1 (Full-speed) USB port
It should also work with the new USB 3.0 ports where the PC will simply
treat the 851C as if it were a USB 2.0 or 1.1 device.
The 851C also supports two USB Audio protocols (not the same as the
port types themselves) USB Audio 1.0 (which works over USB 1.1 ports
and supports up to 24-bit/96kHz) or USB Audio 2.0 (which requires a
USB 2.0 port and can support up to 24-bit/192kHz).
The default configuration is USB 1.1 and USB Audio 1.0 which works
with nearly all common operating systems and computer types without
drivers and supports up to 24-bit/96kHz audio, simply plug in and play.
In this configuration the 851C is able to work at up to 24-bit/96kHz
by declaring to your computer that it can handle any sample rate from
32kHz to 96kHz.
However in some Windows/Mac operating system variants the operating
system itself may restrict or fix the output sample rate or re-sample the
See our online guide at on
USB Audio for more details on this. With careful choice of playback
software and settings many pitfalls can be avoided.
In particular our free Windows USB Audio 2.0 driver (available from our
website) supports up to 24-bit/192kHz audio and WASAPI Exclusive or
ASIO modes that can give enhanced performance.
See the Setup section on how to switch between USB Audio 1.0 and
2.0 modes.
A brief explanation of your choices are below:
Use with PCs
With the 851C switched to USB Audio 1.0 (this is the default setting) the
851C will work with the native Windows XP, Vista or 7 Audio 1.0 driver
(no need to load any new driver) and accept audio up to 24-bit/96kHz.
With the 851C switched to USB Audio 2.0 the 851C needs the Cambridge
Audio USB Audio 2.0 Driver to be loaded and can then accept up to
24-bit/192kHz (and support ASIO and WASAPI Exclusive if required).
The driver is available from
Use with Macs
No extra drivers are required. With the 851C switched to USB Audio 1.0
the 851C will work with the native Mac OS-X 10.5 (Leopard) or above
Audio 1.0 driver and accept audio up to 24-bit/96kHz.
With the 851C switched to USB Audio 2.0 the 851C works with the native
Mac OS-X 10.5 (Leopard) or above Audio 2.0 driver and can accept audio
up to 24-bit/192kHz.
Use with Linux
For most builds of Linux with the 851C switched to USB Audio 1.0 the
851C will work with the native Audio 1.0 driver and accept audio up to
Some very new builds of Linux are now supporting USB Audio 2.0 for
which the 851C should be switched to Audio 2.0 to accept audio up to
For both cases because Linux builds vary according to their creators
choice of software components including drivers it is not possible to
guarantee operation and Audio drivers may need to be loaded.
‘Class drivers’ as they are called for generic support of Audio Class 1.0
or Audio Class 2.0 devices may be available from the Linux community,
we do not supply these.
Bit perfect transfer – ASIO and WASAPI Exclusive
The 851C USB interface hardware and software support bit perfect
Whether or not the audio sent to the 851C is bitperfect (i.e. not resampled
or mixed etc. by the PC) is actually a function of the playback application
and the operating systems audio engine.
By default the standard windows audio drivers (often called WDM
drivers) included in Windows XP support MME or DirectSound transfer,
both of which include a kernel mixer and re-sampler stage.
One way round this is to use ASIO to bypass this. Another is to use a
playback application that supports its own form of kernel streaming, i.e.
if has its own way of outputting the audio without invoking the kernel
For Windows Vista and Windows 7 a new method of audio transfer is
supported called WASAPI. This has two modes; Shared and Exclusive.
Shared mode is similar to MME or DirectSound but in Exclusive mode the
kernel mixer/re-sampler is bypassed and bit perfect transfer is possible
with only one audio playback program directed to the soundcard at a
time (for instance system sounds are not mixed in).
To ensure bit perfect transfer use a playback application that supports
ASIO, WASAPI in Exclusive mode (if you have Windows Vista or Windows
7) or some form of kernel streaming.
This is a fast moving area so we would encourage you to check the web
for the latest media players to support these more audiophile playback
To use ASIO you will need the Cambridge Audio Sound Driver installed and
the 851C switched to USB Audio 2.0.
No further settings are required as the driver automatically supports
ASIO transfer, all that is required is to load and setup suitable ASIO
enabled playback software.
ASIO (Audio Stream Input/Output) is a non Microsoft audio driver
protocol for Windows originally invented by Steinberg ltd ASIO bypasses
some of the normal audio path from the playback application through
the Windows audio system (including the Kernel Mixer) for a more direct
path to the 851C.
You will need to install and use a suitable playback application
that supports ASIO output either natively or via a plugin. One
example of such an application with a suitable plugin is Foobar, see for more details.
Digital Pre-amp Mode
The 851C can optionally be used as a digital pre-amp and connected
directly to a suitable power-amp.
The level at both the balanced XLR and single-ended Phono/RCA outputs
is affected and either connection type can be used, see diagram below.
Before making this connection access the 851C's Digital Volume menu
by pressing the Menu button then using the  and  buttons to move
to the Digital Volume item.
Be careful not to turn Digital Volume off when connected to a power
amplifier in this way as this returns the output level to an un-adjustable
maximum level for use only into an integrated amplifier or pre-amplifier
with its own volume control.
Press the Select button to enter this submenu and use the  and 
buttons to select On.
Finally confirm this setting by pressing the Select button again.
See next section for a full listing of the Menu structure.
Once Digital Volume is enabled, the handset Volume Up and Down
buttons will affect the signal output level from the 851C.
When Digital Volume is enable, a Ch. Balance (Channel Balance) option
is also available in the menu structure.
This allows adjustment of the relative level between left and right
channels for circumstances where one speaker is further away than the
other or the source material itself has a channel imbalance.
XLR cable
Use with an iD100 Digital iPod/iPhone/iPad dock
The 851C can optionally be used with a Cambridge Audio iD100 digital
iPod/iPhone/iPad dock.
Connect the iD100 to a suitable digital input, Digital Input1, Digital
Input2 or AES/EBU Balanced In can be used, we recommend using the
AES/EBU Balanced input for best sound quality.
To operate the iPod/iPhone/iPad in the dock, first select the appropriate
input and then press and hold that same button whilst using the Apple
compatible buttons on the remote.
See the 'Remote Control' section for details.
Operating instructions cont.
Menu structure
Auto Off
Off 5m 10m 15m
On Off
Audio 2 Audio 1
Front IR
On Off
Off On
(Note Only available
if Digital Volume is
Digital 1 Digital 2 AES/EBU
The 851C menu structure has a variety of setup parameters that can
be adjusted to suit both specific installation requirements and personal
preferences. The setup parameters are accessed and modified through
a menu driven interface that uses the 851C display along with its front
panel or handset Menu, Select, Skip ( ) and Stop () buttons.
To enter the 851C setup menu, first press the front panel or handset
Menu button. The first setup parameter (Auto Off), will be shown on the
display. To select further parameters for adjustment press the one of the
front panel or handset Skip ( ) buttons.
With the required parameter selected, press the front panel or handset
Select button. Pressing one of the Skip ( ) buttons will now scroll
through the options available for that parameter. When the required
option is displayed, press the front panel or handset Select button.
The setup option is now stored. To exit from the setup menu interface
press the front panel or handset Menu button to step back through the
The 851C DSP has three different Filter functions: Linear Phase,
Minimum Phase and Steep. All three filters are highly sophisticated
audiophile topologies, optimised specifically for audio playback. In our
opinion, these filters offer excellent sound quality but differ subtly in
optimisation, hence we’ve made all three available to you.
Note: For clarity, all diagrams show the theoretical response of the DSP
itself, excluding any analogue filtering at the DAC output or the antialiasing filter applied during recording and/or mastering of the digital
Linear Phase Filter
Frequency response
Magnitude (dB)
Input Naming – Input Naming enables the display name of the Digital 1,
Digital 2 and AES/EBU inputs to be changed. Use the Skip ( ) and
Select button to select the input name to be changed. Once selected
a flashing cursor will appear beneath the first character to the existing
name. The Play/Pause and Stop () buttons can then be used to scroll
through the available characters. When each desired character is
displayed, use the Skip ( ) buttons to move on to the next character.
Press the Select button to store the new name.
S/W Version – Selecting S/W Version displays the player’s internal
operating software version number and some additional build
information. This information is primarily provided for service personnel.
Front IR – Selecting Front IR enables the 851C front panel infrared
receiver to be switched on or off (if you are using an external IR system
and the IR emitter Input or Control Bus. In the majority of installations
the infrared receiver should be left switched on.
Digital Vol – Digital Volume enables the 851C to operate as a digital
preamplifier and be connected directly to a power amplifier. With Digital
Volume engaged, the remote handset volume buttons (symbols) will
control the 851C analogue output level. Digital Volume is disengaged
(Off) by default and should remain off in most 851C installations. It
should only be engaged (On) if the 851C is installed in an appropriately
configured audio system without a further downstream volume control.
Ch. Balance – Only enabled when Digital Volume is used. A balanced
control is implemented.
Frequency response
The Linear Phase filter is a highly regarded audio filter offering low ripple
in both the pass and stop bands, and what is known as constant group
delay. Constant group delay means that audio signals of all frequencies
are always delayed by the same amount when passing through the filter.
All audio is therefore fully time-coherent at the output.
The trade-off with this type of filter is that due to internal feed-forward
in the DSP, its impulse response will exhibit some pre-ringing. In other
words, when excited with a theoretical impulse, the output has both
a small amount of pre- and post-spike amplitude ringing (albeit well
Frequency response
USB Class – USB Class options enable 851C compatibility with both USB
Audio 1.0 and USB Audio 2.0 interface formats. The default setting is
USB Audio 1.0 which will work driverlessly with most operating systems
for 16-24 bit content at 32-96kHz. Note USB Audio 2.0 requires a driver
to be loaded for Windows. Without this selecting USB Audio 2.0 will
normally give no output . See section on USB Audio for advanced users.
Each setup parameter and its options is described following paragraphs.
Auto Play – WIth Auto Play engaged a CD will begin to play as soon as the
disc drawer is closed. The Auto Play options are Off and On.
Note: The 851C will automatically return to normal play mode if it is left
inactive in setup menu mode for more than a minute.
Auto Off – When Auto Off is engaged the 851C will switch to standby
after a preset time if no audio is playing. The Auto Off options are Off, 5
minutes, 10 minutes and 15 minutes.
Frequency response
Minimum Phase Filter
Steep Filter
Frequency response
Frequency response
Magnitude (dB)
Magnitude (dB)
Linear phase filter
Steep fi ter
frequency/FS (input sampling rate)
frequency/FS (input sampling rate)
The Minimum Phase filter is another highly regarded audio filter that
offers even lower ripple in the pass and stop bands. Unlike the Linear
Phase filter, group delay is not constant; however, phase shift is low and
the particular benefit with this filter is that the impulse response exhibits
no pre-ringing.
Impulse response
Our Steep filter is a linear phase filter that has been optimised for stop
band attenuation of close-in aliasing images. Here we have traded a
little attenuation of the very highest frequency response (-2dB at 20kHz
for 44.1kHz material) and a little more pre- and post-ringing for a very
steep attenuation just outside the pass band. The Steep filter is able
to attenuate aliasing at 22kHz by some 80dB for 44.1kHz material for
Impulse response
Time (samples)
Time (samples)
Note: All filters exhibit the same ultimate roll-off of approximately 140dB.
The following table shows the filter stop band attenuation for 44.1kHz
Linear Phase
Minimum Phase
Roll-off at
Roll-off at
Ultimate roll-off
We encourage you to experiment with the filters to determine which
sound best to your ears and using your source equipment/programme
material. The 851C remembers and recalls the selected filter type for
each input individually, making it possible, for example, to select Steep
for the USB input and Linear Phase for Digital Input 1, and so on.
Operating instructions cont.
Custom installation (C.I.) use
The 851C incorporates a Control Bus input and output that enables unmodulated handset 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 (multiroom) systems or remote IR receiver systems. The Control Bus sockets
are colour-coded orange.
The 851C is a complex product but even so, should things seem not
quite right, the answer is very often a simple one.
An IR Emitter Input is also provided that enables modulated IR handset
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. This feature is useful for multi-room systems (such as
the Cambridge Audio Incognito multi-room system) which feature routed
I.R. emitter outputs. Instead of using window emitters stuck over the
CD players front panel IR receiver, a mono 3.5mm mini- jack to 3.5mm
mini-jack lead can be used for a more reliable electrical connection. An
RS232 port is also featured which allows the 851C to be controlled by
C.I. systems.
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 handset for teaching into C.I. systems as
1. Press and hold the Standby/On button. The remote first generates
it’s standby (toggle) command. Keep the button held down, after 12
seconds a CD player “On” command will be generated. If the button is
kept held down for a further 12 seconds, a CD player “Off” command
is generated.
A full code table and RS232 protocol for this product is available on the
Cambridge Audio website at:
Player will not switch on
Ensure the AC power cord is connected securely.
Ensure the plug is fully inserted into the wall socket and that the socket
is switched on.
Check the fuse in the mains plug or adaptor.
The player will not read the disc
Check the disc is not loaded upside down.
Check that the disc is not scratched or dirty.
There is no sound
Ensure that the amplifier is configured correctly.
Check that the interconnects are inserted correctly.
The disc is skipping
Check that the disc is not scratched or dirty.
Ensure the player is on a firm surface and not subject to vibrations.
There is a hum coming from the speaker
Ensure that all cable connections are secure.
If USB playback, set the USB Ground Lift Switch to “Lift”.
The remote handset will not function
Check that the batteries have not expired.
Ensure that nothing is blocking the remote sensor.
Technical specifications
All measurements are for 24-bit signals via the digital inputs so as not to
be source material limited unless stated.
D/A convertersDual Analog Devices
AD1955 24-bit DACs
Digital filterAnalog Devices Black Fin
ADSP-BF532 32-bit DSP
performing 2nd Generation ATF2
up-sampling to 24-bit 384kHz
Linear Phase, Minimum phase or
Steep modes.
Analog filter2 Pole Fully Differential
Linear Phase Bessel filter
Frequency response
20Hz to 20kHz (+/-0.1dB)
THD @ 1Khz 0dBFs
< 0.0004%
THD @ 1Khz -10dBFs
< 0.0004%
THD @ 20Khz 0dBFs
< 0.0007%
IMD (19/20kHz) 0dBFs
< 0.0002%
Linearity @ -90dBFs
+/- 0.2dB
Linearity @ -120dBF
+/- 0.4dB
Stop-band rejection (>24kHz) > 120dB
S/N ratio, A weighted
> 113dB
Total correlated jitter< 60pS for all digital inputs, CD
playback and USB 2.0
< 180pS for USB 1.0
Crosstalk @1kHz
< -130dB
Crosstalk @20kHz
< -114dB
Output impedance
< 50 ohms
0dB Fs Output2.2Vrms (2.2Vrms each phase for the
balanced output)
Digital Input 1
S/PDIF 75 ohms or TOSLink optical
Digital Input 2
S/PDIF 75 ohms or TOSLink optical
XLR balanced 110 ohms per phase
USB Audio InputUSB Type B conforming to Audio profile
1.0 or USB Audio profile 2.0 (user
USB Maximum Current Rating 500mA.
CompatibilityUSB 1.0:
24-bit 44.1kHz, 48kHz, 96kHz
USB 2.0:
16/24-bit 44.1kHz, 48kHz, 88.2kHz,
96kHz, 192kHz
16/24-bit 32-96kHz
16/24-bit 32-192kHz
CD playback is intrinsically limited to
16-bit 44.1kHz
Dimensions - H x W x D115 x 430 x 360 mm
(4.5 x 16.9 x 14.7”)
Max power consumption
40W (CD playing)
Idle consumption
8W approx
Standby power consumption
10kg (22lbs)
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
© 2012 Cambridge Audio Ltd
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