GENx192 Studio Master Clock
User’s Guide
Safety
User’s Guide
6408 216th Street SW | Mountlake Terrace, WA 98043 USA
T +1.425.778.7728 F +1.425.778.7727 | www.SymetrixAudio.com
2
GENx192 Studio Master Clock
AVIS:
NE PAS OUVRIR
Il ne se trouve a l’interieur aucune piece pourvant entre reparée l’usager.
SEE OWNERS MANUAL. VOIR CAHIER D’INSTRUCTIONS.
S’adresser a un reparateur compétent.
RISQUE DE CHOC ELECTRIQUE
No user serviceable parts inside. Refer servicing to qualified service personnel.
CAUTION
WARNING:
TO REDUCE THE RISK OF FIRE OR
ELECTRIC SHOCK DO NOT EXPOSE
THIS EQUIPMENT TO RAIN OR MOISTURE
DO NOT OPEN
RISK OF ELECTRIC SHOCK
Safety
What Ships in the Box
• AGENx192hardwaredevice.
• Onedetachablepowercord.
• ThisUser’sGuide.
Getting Help
Voice Processor 2x, the Windows
application that controls the hardware,
includes a help module which acts as a
complete User’s Guide for both hardware
and software.
If you have questions beyond the scope
of this Quick Start Guide or the help
module, contact our Customer Support
Group in the following ways:
Tel: +1.425.778.7728
8:00 am to 4:30 pm
Monday through Friday,
Pacific Time
Web: http://www.SymetrixAudio.com
This device complies with part 15 of
the FCC Rules. Operation is subject
to the following two conditions: (1)
This device may not cause harmful
interference, and (2) this device must
accept any interference received,
including interference that may cause
undesired operation.
This Class B Digital apparatus meets
all requirements of the Canadian
Interference-Causing Equipment
Regulations
Cet appariel numerique de la classe
B respecte toutes les Exigences du
Reglement sur le materiel brouilleur
du Canada.
Important Safety
Instructions
! Read these instructions.
@ Keep these instructions.
# Heed all warnings.
$ Follow all instructions.
% Do not use this apparatus near water.
This apparatus shall not be exposed to
dripping or splashing and no objects
filled with liquids, such as vases, shall
be placed on the apparatus.
^ Clean only with dry cloth.
& Do not block any ventilation openings.
Install only in accordance with the
manufacturer’s instructions.
* Do not install near any heat sources
such as radiators, heat registers,
stoves, or other apparatus (including
amplifiers) that produce heat.
( This apparatus shall be connected to
a mains socket outlet with a protective
earthing connection. 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.
BL Protect the power cord from being
walked on or pinched particularly at
plugs, convenience receptacles, and
the point where they exit from the
apparatus.
BM Only use attachments/accessories
specified by the manufacturer.
BN Use only with 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.
BO Unplug this apparatus during lightning
storms or when unused for long
periods of time.
BP Refer all servicing to qualified service
personnel. Servicing is required when
the apparatus has been damaged in
any way, such as power-supply cord
or plug cord is 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.
3
G The lightning flash with arrowhead
symbol within an equilateral triangle
is intended to alert the user of the
presence of uninsulated “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 of the presence of
important operating and maintenance
(servicing) instructions in the literature
accompanying the product (i.e. this
Quick Start Guide).
G CAUTION: To prevent electric shock,
do not use the polarized plug supplied
with the unit with any extension cord,
receptacle, or other outlet unless the
prongs can be fully inserted.
G Power Source: This Symetrix
hardware uses a switching power
supply that automatically adjusts
to the applied voltage. Ensure that
your AC mains voltage is somewhere
between 100-240 VAC, 50-60
Hz. Use only the power cord and
connector specified for the product
and your operating locale. A protective
ground connection, by way of the
grounding conductor in the power
cord, is essential for safe operation.
The appliance inlet and coupler shall
remain readily operable once the
apparatus has been installed.
G User Serviceable Parts: There are
no user serviceable parts inside this
Symetrix product. In case of failure,
customers inside the U.S. should refer
all servicing to the Symetrix factory.
Customers outside the U.S. should
refer all servicing to an authorized
Symetrix distributor. Distributor
contact information is available online
at: http://www.SymetrixAudio.com.
Introduction and Data
Introduction
Every piece of digital audio equipment has an internal sample clock
that controls the timing of the A/D and D/A converters and the transfer
of audio through its digital audio interfaces. For optimal converter
performance, the clock must be stable and free of timing irregularities
known as ‘jitter’ which can induce harmonic distortion and degrade
stereo imaging. Additionally, to transfer digital audio between various
devices the clocks must be synchronized to a common ‘master’ timing
reference, without which clicks, pops and/or low-level noise will occur.
Because most digital audio devices support only a single clock input or
output, many users resort to chaining clock signals from the output of
one device to the input of another. Chaining clocks can lead to clock
phase differences and increased jitter as the signal proceeds down
the chain.
Mechanical Data
Item DESCRIPTION DETAILS
The Lucid GENx192 Ultra Low Jitter Studio Master clock provides
the ideal solution to most common clocking issues found in today’s
recording, post-production, and broadcast environments by providing
a low-jitter clock reference that can be distributed to a large number
of devices simultaneously in multiple industry-standard formats and
sample rates. The GENx192 features eight (8) word clock, four (4) AES
clock, and two (2) S/PDIF clock outputs capable of operating at sample
rates of up to 192 kHz. The outputs are divided into two groups, each
having independent control over sample rate. The GENx192 can also
synchronize to and re-distribute external word clock or AES signals
ranging from 28 to 216 kHz. Finally, it can also function as a 1x4 AES-3
(audio) distribution amplifier.
User’s Guide
Rack Space Required 1U (WDH: 48.02 cm x 22. 15 cm x 4.37 cm / 18.91 in x 8.7 2 in x 1.72 in).
(Depth is specified from front panel to back of connectors.)
Electrical 100-240 VAC, 50-60 Hz, 25 Watts maximum. Universal power input - no line voltage switching
Ventilation Maximum recommended ambient operating temperature is 30 C / 86 F. Ventilation should not be impeded b y covering the
Shipping Weight 3.70 kg / 8.15 lbs.
Allow at least 1 inch a dditional clearance for
rear panel connections. Additional depth m ay be
required depending upon your specific wiring and
connections.
required.
unit with items such as newspapers, tablecloths,
curtains, etc.
Performance Data
Item DESCRIPTION
INPUTS:
Recommended Input Level Word Clock: 2.0 to 5.0 Vpp (nominal); 1.0 to 7.0 Vpp (lock range)
Input Impedance Word Clock: 75Ω / 10kΩ switchable (Green “TERM” LED beneath the switch on rear panel indicates proper Word
AES: 2.0 to 7.0 Vpp (nominal)
Clock input termination)
AES: 110Ω
OUTPUTS:
Output Level Word Clock: 5.2 Vpp, unterminated; 4.0 Vpp, 75Ω termination
AES: > 3.6 Vpp, 110Ω termination
S/PDIF: >0.3 Vpp, 75Ω termination
Output Impedance Word Clock: 24Ω
AES: 110Ω
S/PDIF: 75Ω
Maximum Cable Length Word clock: 5 m / 16.5 ft (with 75Ω RG-59 or better coaxial cable)
AES: 30.5 m / 100 ft (with 110Ω shielded twisted pair cable)
S/PDIF: 10.0 m / 33 ft (with 75Ω RG-59 or better coaxial cable)
6408 216th Street SW | Mountlake Terrace, WA 98043 USA
T +1.425.778.7728 F +1.425.778.7727 | www.SymetrixAudio.com
4
GENx192 Studio Master Clock
Data and Front Panel
Performance Data... continued
Item DESCRIPTION
SYSTEM:
Internal Sample Rates 44.1 kHz and 48 kHz base rates, multiplied by 2x and 4x to 88.2 kHz, 96 kHz, 176.4 kHz, 192 kHz
External Frequency Range 28 kHz to 216 kHz
Clock Skew -- Any Output to Any
Output
TS-75 Word Clock Terminat ion Sensing LEDs indicate condition of clock signals based on known and expected signal voltages and source and load termina-
Clock Divisor Ranges When an external clock falls within the frequency ranges prescribed below, the clock is divided down in order to create
< 1.00%, 28 kHz to 216 kHz, any output to any output
tion conditions
Output Sense: Amber > 4.3 Vpp
4.3 Vpp ≥ Green ≥ 3.5 Vpp
Red < 3.5 Vpp
Input Sense: Amber > 4.4Vpp
4.4 Vpp ≥ Green ≥ 1.4 Vpp
Red < 1.4 Vpp
the base rate for the unit
÷1, 28kHz to 56 kHz
÷2, 56kHz to 112 kHz
÷4, 112kHz to 216 kHz
FRONT PANEL
ITEM DESCRIPTION DETAILS
RATE 8 Green LEDs Displays the current sample clock rate as well as lock status. When SYNC SOURCE is set
to INTERNAL, both the LOCK LED and the corresponding base sample RATE LED (44.1
kHz or 48 kHz) will be lit. When SYNC SOURCE is set to EXTERNAL (AES or WORD), the
LOCK LED be lit when a valid clock signal ranging from 28 kHz to 216 kHz is present; if
no signal is present or the clock is out of range, the LOCK LED will flash to indicate that
the GENx192 is not synchronized to the clock source.
When the external clock rate falls within ± 6.0% of a nominal sample rate, the corresponding RATE LED will flash. When the external clock rate falls within ± 0.2% of a
nominal sample rate, th e corresponding RATE LED will light soli d.
SYNC SOURCE 4 position rotary switch Selects either an internal oscillator (44.1 kHz or 48 kHz) or an external clock source (AES
A OUTPUTS 3 position rotary switch Sets th e sample rate for the A OUTPUTS. When an internal clock is used, the switch
B OUTPUTS 3 position rotary switch Sets the sample rate for the B OUTPUTS. Functions identically to the A OUTPUTS switch.
POWER SWITCH Rocker switch Turns the unit off and on.
or word clock).
multiplies the base rate (set by SYNC SOURCE) by either 1x, 2x, or 4x. However, when an
external clock is used, the switch c an act as either a multiplier or divider, depending on
the rate of the external clock. For example, with an external 96 kHz clock, the GENx192
generates 96 kHz when the A OUTPUT switch is set to 96, 192 kHz when set to 192 (x2),
and 48 kHz when set to 48 (÷2). See CLOCK DIVISOR RANGES for more information.
5
Rear Panel
REAR PANEL
ITEM DESCRIPTION DETAILS
User’s Guide
POWER INPUT IEC 3 prong jack Accepts power from detachable IEC power cable (100-240 VAC, 50-60 Hz, 25 Watts max).
S/PDIF OUT 2 x Female RCA Transmits either AES-3 (audio) or AES-11 (sync) data formatted for unbalanced S/PDIF
AES OUT 4 x Male XLRs Transmits either AES-3 (audio) or AES-11 (sync). When the SYNC SOURCE is set to AES
WORD CLOCK OUT 8 x Female BNCs Transmits phase-aligned CMOS-level word clock signals.
AES IN Female XLR Accepts single-wire AES-3 or AES-11 signals at sample rates between 28 and 216 kHz.
WORD CLOCK IN Female BNC Accepts TTL or CMOS-level word clock signals from 28 to 216 kHz.
TERM (Switch) Push Button Toggle Switch Enables or defeats Word Clock input termination. (Green “TERM” LED beneath the switch
TERM 9 x Bi-color LEDs Displays the condition of the word clock input or output signal using voltage level sensing
Connect only to a grounded power outlet.
operating levels. Functionally identical to AES OUT.
and the OUTPUT switch matches the rate of the incoming AES source, then the AES output
format follows the input format and the GENx192 acts as a 1x2 or 1x4 AES distributor.
indicates proper Word Clock input termination.)
to determine whether or not the signal is present, is operating at the correct levels, and is
terminated properly. An amber LED indicates an overvoltage or underterminated condition;
for outputs, it can also indicate that no connection to a receiving device has been made.
A red LED indicates an undervoltage or overterminated condition; for the input, it can also
indicate that no connection to a source device has been made.
A green LED indicates optimal signal conditions with proper voltage and termination.
However, because less is known about the word clock input signal than the output (due to
variances in standards and methods employed for generating word clock amongst the various equipment manufacturers) the tolerance range for the input is much less restrictive for
the input than the outp ut to accommodate all possible v alid conditions.
6408 216th Street SW | Mountlake Terrace, WA 98043 USA
T +1.425.778.7728 F +1.425.778.7727 | www.SymetrixAudio.com
6
GENx192 Studio Master Clock
Hardware and Connections
POWER:
Connect the IEC connector side of the supplied AC cord to the receptacle on the
rear of the GENx192. Connect the other side of the AC cable to an AC power
source that is of the correct voltage and frequency (100-240 VAC, 50-60 Hz). Use
only the power cord and connector specified for the product and your operating
locale.
INPUTS (optional):
If the GENx192 is being used to distribute an existing clock source, connect
that clock source to either the WORD CLOCK or AES input. Both inputs may be
connected simultaneously but only one input may be selected at a time using the
SYNC SOURCE selection knob on the front panel.
WORD CLOCK:
Using a 75Ω coaxial cable (RG-59 or better) terminated with male BNC
connectors, connect one end to any of the eight GENx192 WORD
CLOCK outputs, and the other end into your destination device’s word
clock input. Repeat as necessary to connect additional devices.
AES CLOCK:
Using a 110Ω shielded, twisted pair cable terminated with one male and one
female XLR connector, connect the female end to any of the four GENx192 AES
outputs and the male end into your destination device’s AES input. Repeat as
necessary to connect additional devices.
NOTE : Be sure that the designated AES input of your destination device can be
configured as an AES sync source for that device.
S/PDIF CLOCK:
Using a 75Ω coaxial cable (RG-59 or better) terminated with male RCA connectors,
connect one end to either GENx192 S/PDIF output and the other end into your
destination device’s S/PDIF input.
NOTE 1: Many consumer and “pro-sumer” devices do not offer Word or AES clock inputs.
However, of those devices, many do have S/PDIF digital audio inputs, such as the
Digidesign 001 and 002 workstations. These devices typically allow the S/PDIF input to be
a sync source while allowing concurrent audio throughput from both the S/PDIF and other
ports (such as ADAT Optical). If your device fits this profile, the GENx192’s S/PDIF output
will allow that device to finally sync to the outside world!
NOTE 3: There is no clock-only specification for S/PDIF digital audio, as there is within
the AES specification. Therefore, the S/PDIF output of the GENx192 is simply an
unbalanced, transformer-coupled copy of the AES outputs. Most S/PDIF inputs will
accept the AES-formatted data, but compatilbility is not always guaranteed.
7
Basic Setup: Front Panel
A/D D/A Converter
WORD IN
WORD IN
Digital Recorder
WORD IN
Digital Mixer
WORD IN
Digital Effects
Device
AES OUT
House Sync
(optional)
A/D D/A Converter
WORD IN
WORD IN
Digital Recorder
WORD IN
Digital Mixer
WORD IN
Digital Effects
Device
AES OUT
House Sync
(optional)
User’s Guide
!
Lock and Rate Indicator LEDs
@
Sync Source Selector
#
A Outputs Sample Rate Multiplier
$
B Outputs Sample Rate Multiplier
%
Power On/Off
Basic Setup - Illustration
This illustration details the connections of a typical master clock setup
in a visual format. In this setup, analog audio is handled by an external
A/D and D/A converter such as a Lucid 88192. After the converter,
all audio is digital between a digital multitrack recording device and a
digital mixer. All devices sync to a dedicated word clock provided by
the GENx192.
The GENx192’s user interface consists of three simple multi-position
selector knobs. Follow the guidelines below to setup the GENx192 for
use in the example shown above.
A. Power on.
B. Select the SYNC SOURCE and set the SYNC RATE:
1. Turn the SYNC SOURCE knob to select the internal base rate of either
44.1 kHz or 48 kHz based upon the desired final output rate. For
example, select 48 if you want 48 kHz, 96 kHz, or 192 kHz. Select
44.1 if you want 44.1 kHz, 88.2 kHz or 176.4 kHz. Both the green
LOCK LED and the 44.1 or 48 green RATE LED rate will light.
2. Turn the A OUTPUTS knob to select the desired final output rate. This
is a multiple (1x, 2x or 4x) of the base selected in step one.
3. Repeat step 2 for B OUTPUTS if necessary.
If you’re connecting the GENx192 to an external sync source then
6408 216th Street SW | Mountlake Terrace, WA 98043 USA
T +1.425.778.7728 F +1.425.778.7727 | www.SymetrixAudio.com
proceed as follows:
A. Power on.
B. Select the SYNC SOURCE and set the SYNC RATE:
1. Turn the SYNC SOURCE knob to AES or WORD. If a valid AES or WORD
2. Turn the A OUTPUTS knob to select the desired final output rate.
3. Repeat step 2 for B OUTPUTS if necessary.
Note: Should the external sync source become disconnected or
interrupted in some way, the GENx192 will switch to an internal clock
that is closest to the exter nal clock rate. The GENx192 will continue to
output sync at the closest inter nal rate until it is once again able to lock
to a valid external source.
8
input is present then the LOCK LED will light. A flashing LOCK LED
indicates that the selected SYNC SOURCE is either not present, out of
range, or unusable. A RATE LED will flash when the external clock rate
falls within ± 6.0% of the indicated RATE. A RATE LED will light solid
when the external clock rate falls within ± 0.2% of the
indicated RATE.
GENx192 Studio Master Clock
Clocks, Cables and Termination
Sample Clocks
Within each piece of digital audio equipment are one or more clocks
that control signal and timing relationships between various internal
components and exter nal devices. The sample clock controls the A/D
and D/A conversion rate and timing of audio signal transfers through
digital interfaces such as AES, TDIF, and ADAT optical. The rate at
which this clock runs is known as the Sample Rate. The most common
‘standard’ sample rates used in professional audio are 44.1 kHz and 48
kHz, from which many other less common rates are derived.
To properly receive a digital signal transmitted from another device, the
sample clocks of both sending and receiving devices must precisely
match each other. To use an analogy, imagine a machine placing parts
onto a conveyor belt, while another machine picks the parts off the
other end of the belt and packages them. If both the first machine and
the belt are running at a constant rate, then the packaging machine
must also take the parts off the line at precisely the same rate. Not
only must the packaging macine run at the identical rate, it must also
pick the part off the belt at the exact moment the part passes it. If the
alignment is out of whack, then even though the packaging macine
runs at the correct speed, it will miss every part.
As everyone knows, if you take two wristwatches, set them to the exact
same time and start them at the same moment, a week later they will
not read the same time. The crystal oscillators used to generate the
sample clock inside each digital audio device are no different - no two
crystal oscillators run at exactly the same rate. Therefore they must
be synchronized externally using a common ‘master’ clock signal that
provides both frequency (rate) and position (alignment) information.
This master clock can be either any digital device in the system, or a
dedicated clock generator such as the GENx192. Most professional
audio equipment, including DAT machines, digital consoles, A/D and
D/A converters, and DAWs can slave their internal sample clock to
an exter nal sample clock, unlike most consumer audio devices which
cannot (such as CD players with digital outputs).
Common Clocking Problems
Insuring proper system synchronization requires not only paying
attention to the software and/or hardware configuration of each device
in the system, but also using the correct interconnection hardware
(cabling, connectors, termination) and employing the appropriate
interconnection topology. Failing to do so may result in any one of a
number of common synchronization problems, some of which are not
readily perceptible or easy to diagnose.
Jitter: Jitter refers to the amount of aperiodicity in a clock signal, and
is generally measured in ‘nanoseconds’ (ns or 10-9 s). For
example, a jitter-free 50 kHz clock has exactly one clock cycle
every 20µs (10-6 s). If the period of this clock changes from
19.997 µs to 20.001 µs from one moment to the next, then the
clock is said to have 4 ns of jitter because the period varies by
4ns.
Jitter degrades the quality of the analog-to-digital and
digital-to-analog conversion process by inducing harmonic
distortion into the signal, and therefore is hard to notice
without comparing it to an ideal (extremely low jitter) signal
within the same listening environment. Jitter can also ‘smear’
the sharpness of a stereo image created with phase-coherent
micing techniques (e.g. stereo-mic’d acoustic guitar). Because
jitter can be considered as a signal that modulates an ideal
clock, it also has a frequency spectrum which affects the
character of the distortion.
Jitter is the cumulative effect of numerous causes, ranging from
poor grounding to the characteristics of the internal circuitry
of the equipment itself (noisy power supplies, signal crosstalk,
circuit components, etc). While some of these factors cannot
be controlled, external factors such as cabling, termination, and
clock distribution method can play a significant contributing
role.
Drift: Drift occurs when two or more audiovisual record/playback
systems (DAW, digital tape, video, etc.) do not share a common
master clock. The problem is a direct consequence of the
wristwatch illustration used above: when two DAWs are both
set to inter nal clocks at the same sample rate, and if they
contain identical audio material and are started at exactly the
same time, then over time one DAW will begin to play back
behind the other. Whereas it may take hours or days for two
wristwatches to drift from each other appreciably, in the digital
world it typically takes only seconds or minutes for noticeable
drift to accumulate. Drift is invariably caused by a failure to set
up the operating parameters of the equipment correctly or to
make the correct synchronization connections.
Pops, Clicks, Hash, and Distortion: Pops and clicks occur when the
clocks between two digitally interconnected devices running at
different clock rates (for reasons stated above) move into and
out of alignment with each other. As misalignment occurs audio
data is ‘dropped’, creating a discontinuity in the audio data.
Similar to the beating of two closely tuned strings, these pops
and clicks occur at the same rate as the difference in speed
between the two clocks. If the clock rate difference is very
slight, then the clocks will undergo a protracted period wherein
data will be dropped, causing a long burst of noise or ‘hash’
instead. In its most extreme forms (when jitter becomes > 5 to
10% of the clock period), jitter can induce the same problems
except that the period and rate of popping and distortion will
be random.
9
Clocks, Cables and Termination
CLOCK OUT 1
MASTER
CLOCK OUT 2
CLOCK IN
SLAVE #1
CLOCK OUT
CLOCK IN
SLAVE #N
CLOCK OUT
CLOCK OUT 1
MASTER
CLOCK OUT 2
CLOCK IN
SLAVE #1
CLOCK OUT
CLOCK IN
SLAVE #N
CLOCK OUT
User’s Guide
In most cases such problems are immediately noticeable, and with
a little listening and a bit of deductive reasoning the source of the
problem can be quickly found. Some problems are less apparent.
Program material, listening levels and monitor systems as well as
certain types of digital interfaces can tend to mask the problem,
which although present, tends to be present at much lower levels in
the material. When the clock rate difference is dramatic (for example
when a system running at 44.1 kHz is interfaced to another running at
48 kHz), then discrete pops and clicks cannot be heard. Instead, the
‘resampled’ signal results in aliasing and severe harmonic distortion
that sounds grainy and ‘digital’, particularly in the high frequencies.
Skew – Skew is a misalignment of two clocks whose rates are
otherwise synchronized. Skew is almost always caused when devices
are synchronized by chaining synchronization signals serially from
one device to the other, instead of to all devices from a single device.
Skew can cause pops and clicks if the receiving device cannot receive
data from the transmitting device because of the particular phase
relationship of the clocks. Skew can also cause timing differences in
the A/D and D/A conversion processes which can cause slight highfrequency phase cancellation and image smearing if phase coherent
material is distributed across the various sources. Skew should
not be a problem in properly designed equipment when the proper
interconnection topology is used.
Malfunction: At worst, some devices cease to pass audio altogether
when they cannot lock to an external clock. In other cases their PLLs
(Phase Locked Loops) may drift to invalid sample rates quite far from
the target sample rate and create all varieties of audible havoc both
internally and with other interconnected audio devices.
Fortunately, employing a low jitter, low skew, centralized master clock
/ distributor like the Lucid GENx192 can solve most, if not all, of the
above mentioned potential problems.
Clock Distribution: Three Common
Approaches
There are several types of sample clock signals commonly used today:
word clock, AES-3, AES-11, S/PDIF, and ADAT Optical. The GENx192
provides all of these except for ADAT Optical. AES-3, S/PDIF, and
ADAT Optical are known as self-clocking interfaces because they
carry both audio signals and clock data which receiving devices can
slave their sample clocks to. Word clock and AES-11 carry no audio
information – they are synchronization signals only.
There are three ways to distribute clock signals: in a serial chain, in a
parallel chain, or in a star configuration. Often times a setup may be a
combination of two or three distribution methods.
Clock Distribution: Star
In a star configuration, a single ‘master’ generator distributes a clock
signal to each device that requires it.
Without exception Star distribution should be used for every device
that has a word clock or AES-11 (i.e. non self-clocking) input. For
Cabling
Always use the correct cabling recommended for each type of clock
signal. Improper cabling can lead to several of the problems described
previously, such as clock signal degradation and jitter. The longer the
cable run, the more critical it is to use the correct cable.
Word Clock: Use 75Ω video coax (RG-59 or RG-6) with properly
matched 75Ω BNC connectors. In a pinch you may substitute 50Ω
coax (RG-58) for very short runs. Any use of 50Ω coaxial cable with a
properly terminated word clock input will cause signal reflections at the
connector that can induce clock jitter.
AES: Use 110Ω shielded, twisted pair digital audio cable. Because
of the extremely high bandwidth of AES signals (up to 25 MHz),
microphone cable should never be used for AES signals, even for very
short runs.
S/PDIF: Use 75Ω video coax (RG-59 or or RG-6) with RCA male
connectors designed for attachment to coaxial cable. Unlike word
clock, 50 Ω coax should not be used.
Belden, Canare, and Mogami all make excellent coaxial and digital
audio cables that work well in these applications.
this reason the GENx192 was designed with a large number of clock
outputs to facilitate a proper star distribution within all but the
most demanding production environments. If at all possible, this is the
way to go!
6408 216th Street SW | Mountlake Terrace, WA 98043 USA
T +1.425.778.7728 F +1.425.778.7727 | www.SymetrixAudio.com
10
GENx192 Studio Master Clock
CLOCK IN
MASTER
CLOCK OUT
CLOCK IN
SLAVE #1
CLOCK OUT
CLOCK IN
SLAVE #N
CLOCK OUT
BNC 75 Ohm
Terminator
CLOCK IN
MASTER
CLOCK OUT
CLOCK IN
SLAVE #1
CLOCK OUT
CLOCK IN
SLAVE #N
CLOCK OUT
BNC 75 Ohm
Terminator
CLOCK IN
MASTER
CLOCK OUT
CLOCK IN
SLAVE #1
CLOCK OUT
CLOCK IN
SLAVE #N
CLOCK OUT
CLOCK IN
MASTER
CLOCK OUT
CLOCK IN
SLAVE #1
CLOCK OUT
CLOCK IN
SLAVE #N
CLOCK OUT
Clocks, Cables and Termination
Clock Distribution: Parallel
In parallel clock distribution (word clock only), the clocks of multiple
devices are connected to the same signal in parallel using “T”
connectors. In a proper parallel setup, the device at the end of the
chain is terminated (low-impedance), and all devices in between are
unterminated (high-impedance) so as not to adversely load the
signal down.
Clock Distribution: Serial
In serial clock distribution, clocks are chained from the output of one
device to the input of another. Serial distribution has several drawbacks
and should be used only for devices that have self-clocking interfaces
(e.g. certain DAT machines and stand-alone CD burners, digital effects
processors, etc.) These drawbacks include:
Signal Degradation: As the signal is passed from one device to
another, the signal quality can become degraded the farther down the
chain it gets.
Clock Skew: Devices may add a small amount of delay to the output
signal causing the clock edge to become progressively misaligned
between each device in the chain.
Added Jitter: Each device has an inherent amount of jitter in its
internal clocks. If the device regenerates the clock rather than passing
it through then the inherent jitter of the device will get added to the jitter
contributed by all previous devices. Any signal quality degradation will
only exacerbate the jitter problem.
Parallel distribution can be used effectively,
but it also has drawbacks:
Termination Problems: Some manufacturers do not clearly mark
the termination (input) impedance of their word clock inputs. Thus
it is quite easy to have two or more devices in the chain which are
both terminated, causing a sharp drop in clock signal level leading
to synchronization failure in one or more devices. The GENx192
termination sensing LEDs are designed to aid in diagnosing problems
with multiple terminated inputs.
Reliability: Having multiple cables and multiple BNC-T connectors in
the chain can lead to a higher incidence of mechanical failure.
Lack of Flexibility: Many devices cannot be unterminated, and
therefore cannot be connected together in the same parallel chain.
11
Clocks, Cables and Termination
User’s Guide
Termination and Word Clock Drive Levels
Unlike AES-3, AES-11, and S/PDIF, there are no published standards
for word clock. While over the years certain common word clock circuit
design practices have emerged, compatibility between manufacturers
is not guaranteed in all cases. Some devices do not have sufficient
output voltage to drive a properly terminated word clock input, while
others require an unusually high input signal voltage to work properly.
When two such devices are mated the result is that the receiving device
may intermittently lose lock or simply not lock at all. The GENx192 was
designed to be compatible with all equipment on the market today.
For ideal word clock transmission conditions to exist, the end of
the cable must be ‘terminated’ with a load impedance that exactly
matches the cable impedance (75Ω.) “Ringing” occurs at the clock
input when there is an impedance mismatch, adding jitter to the signal.
Many devices are by default inter nally terminated with a 75Ω resistor;
others are either user selectable (through a switch or jumper), or are
completely unterminated. Consult the operator’s manual for each piece
of equipment to determine the word clock input impedance. AES and
S/PDIF do not have these termination issues – properly designed AES
and S/PDIF circuits should be correctly terminated already.
For point to point connections (such as in a star configuration), the
word clock input should always be terminated. If the device at the end
of the cable cannot be internally terminated, then an external 75Ω BNC
terminator and BNC-T connector must be installed.
In a parallel configuration only the device at the end of the cable should
be terminated, and all devices in the middle must be unterminated
(high-impedance). A ‘double-termination’ condition results when two
devices on the same clock leg are terminated. This results in drastically
lower clock voltage, and one or more of the units may fail to lock to the
clock.
Interfacing to Analog Systems
Even today where the significant majority of recording and playback
systems are digital, it is still necessary in certain production
environments to synchronize the playback of analog systems such as
VTR and multitrack tape machines to digital systems that require clock
synchronization. In the digital domain, word clock and AES-3/11 are
used as timing references, whereas in the analog domain video signals
are commonly used.
To synchronize a VTR or analog multitrack to a digital system it is
necessary to use a video blackburst signal as the master timing
reference. Blackburst is typically distributed from a single ‘house sync’
or stand-alone blackburst generator. Most digital systems do not have
video sync inputs. It is therefore necessary to use a second clocking
device that can receive a video signal and output a ‘resolved’ digital
sample clock that can be distributed through a device such as the
GENx192 to all the digital equipment that requires it; a few generators
can output both blackburst and resolved sample clock signals. These
resolvers work as synchronization ‘gearboxes’ by mathematically
relating the video signal to the sample clock. For example, a resolver
can generate a 48 kHz sample clock from a 30 Hz video signal by
outputting (48,000/30) = 1600 samples for every video frame.
Some DAWs and MDMs have video sync inputs as well as clock inputs.
It is acceptable to use the video sync inputs on these devices in lieu
of clock ONLY when using analog inputs and outputs exclusively, AND
when phase-coherent audio is NOT distributed between the video
synchronized devices(s) and other devices in the system. In all other
cases, a valid clock system must be used, particularly when using
digital inputs and outputs. The reason for this is that in most video
resolving circuits, although the video frame rate can be adequately
resolved to the sample clock rate, the phase alignment between
the video and clock signals is arbitrary. Therefore, if two devices are
interconnected digitally but both resolved to black burst, the clock
alignment will be arbitrary and may cause misclocking.
6408 216th Street SW | Mountlake Terrace, WA 98043 USA
T +1.425.778.7728 F +1.425.778.7727 | www.SymetrixAudio.com
12
GENx192 Studio Master Clock
6408 216th St. SW, Mountlake Terrace, Washington, USA,
Safety requirements for mains operated electronic and related
Electromagnetic compatibility - Generic emission standard
Part 1: Residential, commercial, and light industry.
Electromagnetic compatibility - Generic immunity standard
Part 1: Residential, commercial, and light industry.
Declaration of Conformity
Declaration of Conformity
We, Symetrix Inc.,
declare under our sole responsibility that the product:
GENx192 Ultra Low Jitter Studio Master Clock
to which this declaration relates,
is in conformity with the following standards:
EN 60065
apparatus for household and similar general use.
EN 55103-1
EN 55103-2
The technical construction file is maintained at:
Symetrix, Inc.
6408 216th St. SW
Mountlake Terrace, WA, 98043
USA
The authorized representative located within the European Community is:
World Marketing Associates
P.O. Box 100
St. Austell, Cornwall, PL26 6YU, U.K.
Date of issue: January 06, 2006
Place of issue: Mountlake Terrace, Washington, USA
Authorized signature:
Dane Butcher, President, Symetrix Incorporated.
13
Warranty and Service
User’s Guide
The Symetrix Limited Warranty
Symetrix, Inc. expressly warrants that the product will be free from
defects in material and workmanship for two (2) years from the date the
product is shipped from the factory. Symetrix’s obligations under this
warranty will be limited to repairing or replacing, at Symetrix’s option,
the part or parts of the product which prove defective in material or
workmanship within two (2) years from the date the product is shipped
from the factory, provided that the Buyer gives Symetrix prompt notice
of any defect or failure and satisfactory proof thereof. Products may be
retur ned by Buyer only after a Return Authorization number (RA) has
been obtained from Symetrix. Buyer will prepay all freight charges to
retur n the product to the Symetrix factory. Symetrix reserves the right
to inspect any products which may be the subject of any warranty claim
before repair or replacement is carried out. Symetrix may, at its option,
require proof of the original date of purchase (dated copy of original
retail dealer’s invoice). Final determination of warranty coverage lies
solely with Symetrix. Products repaired under warranty will be returned
freight prepaid via United Parcel Service by Symetrix, to any location
within the Continental United States. Outside the Continental United
States, products will be returned freight collect.
The foregoing warranties are in lieu of all other warranties,
whether oral, written, express, implied or statutory. Symetrix, Inc.
expressly disclaims any IMPLIED warranties, including fitness
for a particular purpose or merchantability. Symetrix’s warranty
obligation and buyer’s remedies hereunder are SOLELY and
exclusively as stated herein.
This Symetrix product is designed and manufactured for use in
professional and studio audio systems and is not intended for
other usage. With respect to products purchased by consumers for
personal, family, or household use, Symetrix expressly disclaims
all implied warranties, including but not limited to warranties of
merchantability and fitness for a particular purpose.
This limited warranty, with all terms, conditions and disclaimers set forth
herein, shall extend to the original purchaser and anyone who purchases
the product within the specified warranty period.
Symetrix does not authorize any third party, including any dealer or
sales representative, to assume any liability or make any additional
warranties or representation regarding this product information on behalf
of Symetrix.
This limited warranty gives the buyer certain rights. You may have
additional rights provided by applicable law.
Note: Some Symetrix products contain embedded software and may
also be accompanied by control software intended to be run on a
personal computer. Said software is specifically excluded from
this warranty.
Servicing Your Symetrix Product
If you have determined that your Symetrix product requires repair
services and you live outside of the United States please contact your
local Symetrix dealer or distributor for instructions on how to obtain
service. If you reside in the U.S. then proceed as follows:
Return Authorization
At the Symetrix factory, Symetrix will perform in-warranty or out-ofwarranty service on any product it has manufactured for a period of
three (3) years from date of discontinued manufacture.
Before sending anything to Symetrix, please contact our Customer
Service Department for a Return Authorization (RA) number. The
telephone number is +1.425.778.7728. Additionally, support is available
via the web site: http://support.SymetrixAudio.com.
In-warranty Repairs
To get your Symetrix product repaired under the terms of the warranty:
1. Call us for an RA number (have the serial number, shipping and contact
information and description of the problem ready).
2. Pack the unit in its original packaging materials.
3. Include your name, address, daytime telephone number, and a brief
statement of the problem.
4. Write the RA number on the outside of the box.
5. Ship the unit to Symetrix, freight prepaid. We do not accept freight
collect shipments.
Just do these five things, and repairs made in-warranty will cost you only
one way freight charges. We’ll pay the return freight.
If you don’t have the factory packaging materials, we recommend using
an oversize box. Wrap the unit in a plastic bag, surround it with bubblewrap, and place it in the box surrounded by Styrofoam peanuts. Be sure
there is enough clearance in the box to protect the rack ears. We won’t
retur n the unit in anything but Symetrix packaging for which we will have
to charge you. If the problem is due to operator misuse or error, you will
have to pay for both parts and labor. In any event, if there are charges
for the repair, you will pay for the return freight. All charges will be COD
unless you have made other arrangements (prepaid, Visa or Mastercard).
Out-of-warranty Repairs
If the warranty period has passed, you’ll be billed for all necessary parts,
labor, packaging materials, and freight charges. Please remember, you
must call for an RA number before sending the unit to Symetrix.
Limitation of Liability
The total liability of Symetrix on any claim, whether in contract, tort
(including negligence) or otherwise arising out of, connected with, or
resulting from the manufacture, sale, delivery, resale, repair, replacement
or use of any product will not exceed the price allocatable to the
product or any part thereof which gives rise to the claim. In no event will
Symetrix be liable for any incidental or consequential damages including
but not limited to damage for loss of revenue, cost of capital, claims of
customers for service interruptions or failure to supply, and costs and
expenses incurred in connection with labor, overhead, transportation,
installation or removal of products, substitute facilities or supply houses.
6408 216th Street SW | Mountlake Terrace, WA 98043 USA
T +1.425.778.7728 F +1.425.778.7727 | www.SymetrixAudio.com
14
GENx192 Studio Master Clock
15
Item No. 53-0023
GENx192 Studio Master Clock User’s Guide
© 2008 Symetrix, Inc. All rights reserved. Printed in the United States of America. The information in this document is subject to change without notice.
Symetrix, Inc. shall not be liable for technical or editorial errors or omissions contained herein; nor is it liable for incidental or consequential damages
resulting from the furnishing, performance, or use of this material. Mention of third-party products is for informational purposes only and constitutes
neither an endorsement nor a recommendation. Symetrix assumes no responsibility with regard to the performance or use of these products. Under
copyright laws, no part of this brochure may be reproduced or transmitted in any form or by any means, electronic or mechanical, without permission
in writing from Symetrix, Inc. If, however, your only means of access is electronic, permission to print one copy is hereby granted. The following are
either Trademarks or Registered Trademarks of Symetrix, Inc.: Symetrix, SymNet, SymNet Designer, SymLink and CobraLink. Windows is a Registered
Trademark of Microsoft, Inc.. Other product names mentioned herein may be trademarks and/or registered trademarks of other companies and are
property of their respective owners.
6408 216th Street SW | Mountlake Terrace, WA 98043 USA
T +1.425.778.7728 F +1.425.778.7727 | www.SymetrixAudio.com
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