Cedar DC-1 De-Clicker User manual

CEDAR
Professional Hardware Systems
DC-1 De-Clicker
Digital Audio Restoration System
OWNER'S MANUAL
© 1993 CEDAR Audio Ltd. Written by Gordon Reid

TABLE OF CONTENTS
TABLE OF CONTENTS 2
INTRODUCTION 3
THE BACKGROUND TO SCRATCH REMOVAL 4
SAFETY INSTRUCTIONS 5
SETUP 7
1. Unpacking and Inspection 7
2. Installation site 7
3. Rack Mounting 7
CONNECTIONS 8
1. Before Connection 8
2. Power Connections 8
3. Signal Lead Connections 9
4. Other Connections 10
SAMPLE INSTALLATION IDEAS 11
LOCATION AND FUNCTION OF FRONT PANEL INDICATORS AND
CONTROLS 12
QUICK TOUR 14
WARMSTART AND COLDSTART
15
OPERATING THE CEDAR DC-l 16
Dedicated Controls 17
Threshold Control Page 19
Input/ Outpu t Control Page (II 0 control) 21
Remote Control 23
MIDI 23
RS-232 23
NOTES AND HINTS TO USERS 24
RS-232 PROTOCOL 25
MIDI PROTOCOL 26
SELF TEST MODE 27
Button testing routine 27
Attenuation knob test 27
LED test 28
Spin wheel test 28
DSP memory test board 1 28
DSP memory test board2 28
Test Competed 29

INTRODUCTION
Thank you for purchasing the CEDAR DC-1 De-clicker. This is the world's first
dedicated digital de-clicking device, and offers processing power and performance
that could only previously be obtained using digital signal processors (DSPs)
installed in desk-top (or larger) computer systems such
as the CEDAR Production
Systems. The system is designed for professional use, although
it will work perfectly
well
in a domestic environment, and its features include the following:
Digital Audio interfaces conforming to the AES/EBU and SP-DIF standards.
24-bit input and output resolution when using AES/EBU interfaces
Three digital sampling rates supported: 32kHz,
44.1 kHz and 48kHz
2 analogue sampling rates supported:
44.1 kHz and 48kHz
Balanced (nominal) +4dBm analogue inputs and outputs for connection to
professional analogue equipment.
Unbalanced (nominal) -10dBm analogue inputs and outputs for connection to
domestic analogue equipment.
AID and D/A converters using the latest 64x over-sampling b. -I (Delta-Sigma)
technology.
Mountable
in a 19" EIA rack.
Remote control via MIDI and RS-232 interfaces.
Input and output LED bar-graph
VU meters.
Twin 40-bit floating point DSP processors delivering 50MFIops to handle the
most complex audio processing requirements.
High levels of artificial intelligence designed into the
DC-1 program algorithms
make
it extremely simple to use.

THE BACKGROUND TO SCRATCH REMOVAL
The term 'scratch' is often used to describe many different audio phenomena -ticks,
pops, clicks, crackle and thumps -as well as genuine scratch-like artefacts.
However, when analysed carefully, each of these degradations displays different
sonic characteristics. Therefore, a single process attempting to remove all of these
impulses would be
an unacceptable compromise, incapable of total repair of any
single category.
These degradations can be separated into three categories: thumps (which includes
loud pops), scratches (including ticks and clicks), and crackle. The
DC-1 has been
designed to perform real-time scratch removal.
The operation of the
DC-1 is totally digital, and any signal presented to the analogue
inputs is internally converted to a suitable digital format by the analogue-to-digital
converter (ADC). Following click removal the processed signal is then converted
back from digital format to analogue by the internal digital-to-analogue converter
(DAC).

SAFETY INSTRUCTIONS
CAUTION:
1. Read all of these instructions
All safety and operating instructions should be read before the DC-1 is
operated.
2. Save these instructions for future reference.
3. Follow all warnings and instructions.
4. Water and Moisture
The DC-1 should not be used near water, and must not be exposed to rain or
moisture. If the DC-1 is brought directly from a cold environment into a warm
one, moisture may condense inside the unit. This,
in itself, will not damage
the DC-1, but may cause hazardous electrical shorting to occur. This could
severely damage the DC-1, and even cause danger to life. ALWAYS allow
time for the DC-1 to naturally reach ambient temperatures before connecting
the mains power.
5. Mounting
The DC-1 should be carefully mounted in a 19" EIA rack, or placed on a flat,
stable surface.
If used on a cart or free stand, care should be taken when
moved: uneven surfaces
or excessive force may cause cart and DC-1 to
overturn. Do not position the
DC-1 in a place subject to strong sunlight,
excessive dust, mechanical vibration or periodic shocks.
6. Wall or Ceiling Mounting
The DC-1 has not been designed for mounting directly to walls or ceilings.
7. Ventilation
Good air circulation is essential to prevent internal heat built-up within the DC-
1. The DC-1 should be situated so that its position does not interfere with its
proper ventilation. The DC-1 should not be placed
in any situation which
impedes the flow of air through the fan at the rear. Do not place the DC-1 on a
soft surface.
8. External Heat Sources
The DC-1 should be installed away from significant heat sources such as
radiators, and (if possible) away from other audio devices such as amplifiers
that produce large amounts of heat. Installation in racks with devices such as
signal processors or tape machines should not be a problem.
9. Power Sources
The voltage selector switch must be set to the correct voltage before the
DC-1 is connected to any power supply.
Suitable supplies are 11 Ov and 220/240v, 50Hz or 60Hz AC only.

10 . Grounding or Polarisation
The
DC-1 should always be grounded (or 'earthed').
11 . Power Cord Protection
Power connectors should
be routed so that they will not be walked on or
pinched.
12. Extended Periods of Non-Use
The
DC-1 is not disconnected from the mains power as long as it is
connected to the wall outlet, even
if the unit itself has been switched off.
Therefore, if the
DC-1 is not to be used for an extended period of time, unplug
the unit from the wall. Pull the connector out by the plug, never by the cord
itself.
13 . Cleaning
Clean only with a dry cloth. I\lEVER use liquid cleaners such as alcohol or
benzene
on the DC-1. NEVER use abrasive pads on the DC-1.
14. Damage Requiring Service
The
DC-1 should be returned to qualified service personnel when:
objects have fallen into the unit
liquid has been spilled into the unit
the unit has been exposed to rain
the unit fails to function or appears to operate abnormally
the unit has been dropped, or the case damaged.
15. Servicing
The user should not attempt
to service the DC-1 beyond the instructions
contained
in the User's Manual. All other servicing should be referred to
qualified service personnel.

SET UP
1. UNPACKING AND INSPECTION
Be careful not to damage the DC-1 during unpacking. Save the carton and all
packing materials since you may need them to transport the
DC-1 in the
future.
In addition to the packaging, the carton should contain the following:
mains connection lead
this manual
2. INSTALLATION SITE
The DC-1 may be used in most areas, but to maintain reliability and prolong
operating life observe the following environmental considerations:
Nominal temperature should be maintained between 5° and 35°
Centigrade
(41 ° and 95° Fahrenheit).
Relative humidity should be
in the range 30% to 60% non-condensing.
Strong magnetic fields should not exist nearby.
3. RACK MOUNTING
The DC-1 can be mounted in a standard 19" EIA rack.

CONNECTIONS
The DC-1 may be connected to most domestic and professional audio equipment
currently available. Four types of input and output are provided (two analogue and
two digital) and these will satisfy most users' interconnection requirements. Full
descriptions of these connectors will be found later
in the manual.
1. BEFORE CONNECTION
Before making any connection ensure that the voltage selector on
the back of the
DC-1 is set to the voltage of the local mains
supply. Failure to do so may result
in severe damage to the DC-1
and other equipment connected to it.
Acceptable mains frequencies are 50Hz and 60Hz.
To prevent problems and possible equipment damage, turn off all
power to all equipment before making connections.
Be sure to insert plugs firmly into sockets. Loose connections may
cause hum and noise.
When unplugging any lead, do
so by grasping the plug, not the lead.
2. POWER CONNECTIONS
Before making any connection ensure that the voltage selector on the
back of the DC-1 is set to the voltage of the local mains supply. Failure
to do so may result
in severe damage to the DC-1 and other equipment
connected to
it.
Acceptable mains frequencies are 50Hz and 60Hz.
Ensure that the
DC-1 is switched OFF on the front panel before inserting the
mains lead.
NOTE: Users with 2-pin mains supplies:
When the
DC-1 is connected to other audio components, the AC hum of the
unit may
be increased or decreased by reversing the direction of the power
connector
in the socket. Check that the cord is in the favourable position ('in-
phase') with respect to other audio devices
in the chain. This will ensure that
the best sound quality is obtained from your DC-1.
For further information on grounding and polarity consult a person familiar
with studio grounding techniques.

3. SIGNAL LEAD CONNECTIONS
Refer to the Rear Panel diagram:
The
OC-1 offers four audio connection standards:two analogue and two
digital. These are:
unbalanced analogue audio I/O
balanced analogue audio I/O
digital SP-OIF format audio data
digital AES/EBU format audio data
Note that the OC-1 passes its output
to all four signal outputs irrespective of
the input used.
(i) Unbalanced analogue audio va (See 1, 2 & 8)
This standard is used on domestic and semi-professional audio
equipment such as turntables,
CO players, and cassette decks.
Connect the output from your source
to the unbalanced analogue input
using standard RCA (phono) plugs.
You will require two connectors:
one for each channel.
The unbalanced audio output may be used to connect the
OC-1 to
audio equipment such as amplifiers, cassette recorders, and reel-to-
reel recorders.
It is also possible to connect powered, or 'active'
speakers to this output. Use caution
if you attempt this. The OC-1 has
no volume control in the conventional sense, and speaker (or ear)
damage may occur
if a high amplitude signal is passed through the
OC-1 to the speaker inputs. If in doubt, contact your dealer for advice.
(ii) Balanced analogue audio va (See 1, 2 & 8)
This standard is used in professional audio equipment. Connect the
output from your source to the balanced analogue inputs of the
OC-1
using standard XLR plugs. Note that you will require two such
connections: one for each channel.
The balanced audio output may be used to connect the
OC-1 directly
to audio equipment such as mixing desks and professional recorders
featuring balanced
XLR inputs.
(iii) Digital SP-DIF format audio data (See 3 &4)
The digital SP-OIF format is used by domestic and semi-professional
digital audio devices including
OAT machines, some AOCs, and some
CD players. Both channels of audio are carried along a single cable, so
you may connect the SP-OIF output from your source to the SP-OIF
input of the
OC-1 using a single cable terminated with RCA (or 'phono')
plugs.
The SP-OIF output of the
OC-1 may be connected to the SP-OIF input
of your recording device or external
OAC .

(iv) Digital AESIEBU format audio data (See 4 & 5)
The digital AES/EBU format is used by professional digital audio
devices including mastering systems, DASH recorders, and high
quality
ADCs & DACs. Both channels of audio are carried along a
single cable, so you may connect the AES/EBU output from
your
source to the AESIEBU input of the DC-1 using a single cable
terminated with XLR plugs.
The AES/EBU output of the DC-1 may be connected to the AES/EBU
input of
your digital mixer, recording device or external DAC.
24-bit Digital data resolution:
The DC-1 features 24-bit input and output resolution whenever the
AES/EBU digital inputs and outputs are utilised.
4. OTHER CONNECTIONS
(i) SMPTE (See 6)
An optional SMPTE interface is planned for the DC-1 . The standard
DC-1
does not feature a SMPTE interface, and these connectors have
no function.
(ii) MIDI INlOUTrrHRU (See 9)
The operation of the DC-1 may be controlled using the Musical
Instrument Digital Interface (MIDI). Refer to the chapter on MIDI for
further instructions.
(iii) RS-232 (See 10)
The DC-1 may be controlled using the standard RS-232 computer
communications serial protocol. Refer to
the chapter on RS-232 for
further instructions.

SAMPLE INSTALLATION IDEAS
analogue or
digital in
analogue or analogue or
line out ogital in
digital out
I
TURNTABLE OR
TAPE MACHINE
J I
DC-l
I I
RECORDER
line in
I
AMP
I
1
-
1. OC-1 used in-line for transcription or broadcast purposes.
analogue or
analogue or
analogue or
line out
DC-l
digital in
digital out digital in
SOURCE MIXER
eNects return
fine in
AMP
2. OC-1 used on the effects loop within a studio environment.
analogue or
analogue or analogue or analogue or
analogue or
line out digrtal in
dgtalo ut
digrtal in
digital out
dignal in
SOURCE
DC-1
... ...
CEDAR
RECORDER
or other workstation/editor
....
....
....
....
.....
IiiiiiI IiiiiI
line in
AMP
-
IoiiiiiI
-
3. OC-1 used in-line prior to an editor or audio workstation.

LOCATION AND FUNCTION OF FRONT PANEL
INDICATORS AND CONTROLS
Refer to the Front Panel diagram:
1. Power Switch
2. Input Signal Meters (Left and Right)
Calibrated signal meters display the RMS value of incoming analogue signals.
These meters do not respond to digital signals.
The peak meters will light
if the incoming signal approaches a level likely to
cause clipping
in the digital processing stages.
3. Output Signal Meters (Left and Right)
Calibrated signal meters display the RMS value of all output signals.
The peak meters will light
if the amplitude of the digital signal approaches the
clipping level.
4. LCD Screen
Provides you with a variety of information and messages, keeping you aware
of what
is currently happening in the DC-1.
All the control screens of the DC-1 are displayed on the LCD screen. Please
refer to the following chapters for full instructions.
5. Status Indicators
Indicate the status of the analogue and digital inputs, and whether the DC-1 is
in idle or processing modes.
6. Defined Function Keys.
Certain functions are fundamental to operating the DC-1, and these are
controlled by the defined function keys: Bypass, Page, Pre/Post, and Enter.
7. a-dial
The a-dial enables you to increase and decrease control values. Please refer
to the following chapters for full instructions.
8. Headphone Socket
For use with stereo headphones only, takes a standard 1/4" stereo jack plug.
DO NOT use 2-conductor mono headphones with the
DC-1 .
9. Headphone Level Control
Use this to adjust for a satisfactory listening level. This level control will not
alter the signal level
at any of the rear panel outputs.
10. Input Level Control
This control acts upon the analogue inputs only. Use it to adjust the volume of
incoming signals to the desired level. We recommend a peak level of
approximately 0 to -3dB as shown on the Input Signal Meters.

11. Output Attenuation Control
On occasion, the DC-1 will restore a signal that would, had it not been
damaged by clicks and scratches, have exceeded the digital
1/0 maximum
amplitude. This restoration of the full amplitude can lead to digital clipping.
Avoid clipping using the Output Attenuation Control. This will 'fit' the signal
within digital limits. This Control is not a compressor or limiter.
It acts purely
as a digital gain control.
12. Function Keys
Use along with the LCD screen. Please refer to the following chapters for full
instructions.
13. Contrast Control
The LCD screen may be adjusted for optimum visibility. Use a fine
screwdriver to make such adjustments.

QUICK TOUR
If you are impatient to hear some immediate results using your DC-1 the following
instructions should have you
up and running within a few minutes:
1. Connect the DC-1 to the mains supply, and check that the voltage selected on
the unit corresponds to that of the mains supply.
2. Connect your input and output devices to the DC-1 using the appropriate
input and output sockets. (If
in doubt, please refer to the section
'CONNECTING THE
DC-1 and the manuals of your other equipment).
3. Switch
on the DC-1.
4. If you are using analogue inputs press PAGE once. Press B to select
'analogue'. Then press PAGE twice more.
[If you are using digital inputs ignore this instruction and proceed directly to 5.]
5. If you are using digital inputs press PAGE once. If outputting to a consumer
format machine such as a low-cost
OAT recorder press A to select
CONSUMER format.
[The
DC-1 defaults to PROFESSIONAL format, so do not press A if
connected to a system such as the Sony PCM1630.]
6. Play your material.
7. Press PRE/POST to hear
an immediate difference between the processed
and unprocessed signals (assuming, of course, that your original material
suffers from clicks and scratches).
This section should have whetted your appetite,
so you should now proceed to the
rest of the manual to ensure that you can obtain the best results from your CEDAR
DC-1 .

WARMSTART AND COLDSTART
The DC-1 features Warmstart and Coldstart options. Warmstart has been added so
that the unit can be configured once, and these parameters are then automatically
recalled on every power-up. This is ideal for applications where time-consuming set-
ups at the start of each session are not practical.
Coldstart
If the DC-1 has not been used for some time the system will automatically Coldstart.
This processes initialises all parameters to their factory default values, and
automatically enters at Page 1.
On start-up the message 'Coldstart' will be displayed at the top right of the start-up
screen
on the LCD display. The screen will then enter PAGE 1, which will show the
default Scratch Parameters:
The default values are: Threshold = 10
Mode = Small
Other default values are: Input = Digital
Output = Post processing
MIDI = OFF (Channel
1)
Bypass = OFF
Output format = Professional
A to 0 frequency =
44 .1kHz
Warmstart
The DC-1 remembers the latest parameters used, and the page that was active at
the time that the system was last switched off.
On start-up the
DC-1 will display the message 'Warmstart' on the screen, and then
re-enter at the appropriate page, with all user parameters set to their previous
values.
User Coldstart
If you wish to force the DC-1 to Coldstart, hold down Function Key F1 while
switching on the system. Release
F1 when the message Coldstart is seen on the
LCD display.

OPERATING THE CEDAR DC-1
The DC-1 has three 'pages' which control all aspects of its operation. Each page is
displayed on the LCD screen, and may be controlled using the Function Keys and
the a-dial.
Switch the
DC-1 on. (Refer first to the safety instructions.)
The screen will immediately enter PAGE
1, which will initially show the default
Scratch Parameters.
All the controls for the DC-1 are contained in three 'PAGES', each of which is
selected by pressing the dedicated PAGE function key. The Pages are cycled, and
will appear
in the following order:
Threshold Control Page
I/O Control Page
Remote Control Page
These, and a description of the Dedicated Controls, are now covered in turn:

DEDICATED CONTROLS
The OC-1 features a number of dedicated controls to speed operation. These are:
Dedicated Function Keys:
Bypass
Page
Pre/Post
Enter
va Level Controls
Input Level
Output Attenuation
These are now explained
in turn:
Bypass
It may be desired to completely bypass the operation of the OC-1. Press BYPASS to
do this. The current status will be indicated on the Status LED.
NoteL The Bypass is implemented in software. There is a 1.3mS (analogue to
analogue) or O.15mS (digital to digital) delay in anysignal passed through
the OC-1
in Bypass mode.
All delays are 'group delays'
(i. e. are constant at all frequencies) and are
measured at a sample rate
of 44.1kHz.
Note2: The Bypass does not 'hard-wire' the input
to the output. Analogue signals
still pass through the A
toO and otoA stages.
Page
Use this Function Key to move between Control Pages.
PreIPost
It will often be useful to compare the original signal with the post-processing output
of the OC-1. This Function Key toggles between output modes. The current status
will be indicated on the Status
LEOs.
Enter
The ENTER Key functions as a 'set' command, disabling the a-dial to stop accidental
adjustment of scratch parameters. Press the ENTER Key once to lock out the a-dial.
To re-enable the system, select whichever parameters you wish to adjust using the
appropriate Function Keys under the LCD screen.

Input Level
This control acts upon the analogue inputs only. Use it to adjust the volume of
incoming signals to the desired level. We recommend a peak level of approximately
oto -3dB as shown on the Input Signal Meters.
Output Attenuation
On occasion, the DC-1 will restore a signal that would, had it not been damaged by
clicks and scratches, have exceeded the digital I/O maximum amplitude. This
restoration of the full amplitude can lead to digital clipping.
Avoid clipping using the Output Attenuation Control. These will 'fit' the signal within
digital limits. This Control is not a compressor
or limiter. It acts purelyas a digital
gain control. The Gain is variable from
OdB to -10dB in 1dB steps.

PAGE 1: THRESHOLD CONTROL PAGE
Access this page by pressing the Defined Function Key 'PAGE'.
Threshold Level
This determines the size of scratch removed by the DC-1. A high threshold tells the
system to remove only the largest clicks and scratches, while a lower threshold also
removes fine ticks and clicks.
WARNING: If the threshold for a given piece of music is too low, distortion of
the genuine signal may result.
Typical thresholds to use are as follows:
Large scratch removal:
Large click removal:
Smaller click removal:
Very small tick removal:
20+
15
8
5
Increase or decrease the threshold by turning the a-dial clockwise or anticlockwise
(respectively).
To adjust the Channels individually:
At tile bottom of the screen you will find three items of information. These are:
the Left Threshold (numeric value)
the Mode
the Right Threshold (numeric value)
You will note that both thresholds are surrounded by boxes. This shows that they are
SELECTED, and that the action of the a-dial applies to both channels.
To de-select a channel (and to re-select
it as desired) press the Function Key
immediately below the read-out. The box will disappear, showing that the channel is
now DE-SELECTED.
If both channels are de-selected the a-dial will have no effect.
Mode
The CEDAR DC-1 can optimise its scratch removal depending on whether the
material being processed suffers predominantly from large scratches, or from
smaller ticks and clicks. The Scratch Mode parameter enables you to select the most
appropriate setting for each restoration:

Small : Use this setting when the damage is predominantly small clicks and
ticks.
Medium: This
is a compromise setting lying between the 'small' and 'large'
settings.
Large: Use this setting when the material suffers from larger 'thump'-like
scratches.
Press the Function Key under the word MODE
to toggle between the Scratch Mode
settings.
WARNING: Signal degradation may occur if an inappropriate Scratch Mode setting
is used.