Model 85 AES/EBU Digital
Audio Distribution Amplier
User Guide
Issue 4, June 2011
This User Guide is applicable for serial numbers:
Model 85 M85-00151 and later
Copyright © 2011 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50211-0611, Issue 4
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Table of Contents
Introduction ................................................................... 5
What This User Guide Covers ...................................... 5
System Overview.......................................................... 5
Installation .................................................................... 6
Conguration ................................................................ 8
Operation ...................................................................... 8
Troubleshooting ............................................................ 8
Specications ............................................................... 10
Block Diagram
Model 85 User Guide Issue 4, June 2011
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Issue 4, June 2011 Model 85 User Guide
Page 4 Studio Technologies, Inc.
Introduction
The Model 85 AES/EBU Digital Audio
Distribution Amplier is designed by Studio
Technologies as part of its Studio Tools
group of audio support products.
Designed for a wide variety of recording,
production, broadcast, and duplication
applications, the Model 85 has two AES/
EBU inputs and eight AES/EBU outputs.
All Model 85 functions meet or exceed the
performance of the most expensive “high
end” audio equipment.
What This User Guide Covers
This User Guide is designed to assist you
when installing, conguring, and using the
Model 85 AES/EBU Digital Audio Distribu-
tion Amplier.
System Overview
The Model 85 provides two AES/EBU
digital audio inputs and eight AES/EBU
outputs. Each of the eight outputs provides
a fully isolated reproduction of either input.
Output source selection is provided by
front-panel DIP switches. The Model 85
allows AES/EBU signals to be distributed
to multiple inputs (receivers) without incurring data transmission errors.
A typical application would use the Model
85 to distribute the AES/EBU output of a
digital audio workstation (DAW) to devices
such as DAT or CD recorders, audio/video
storage systems, tie lines to other facilities,
etc.
operation. Components and construction
standards make the Model 85 suitable
for continuous operation, even for on-air
broadcast applications.
AES/EBU Inputs
Each of the two inputs have transformer
coupling and DC voltage blocking. An LED
status indicator is associated with each
input, lighting whenever digital information
is present.
AES/EBU Outputs
The Model 85 contains eight independent
AES/EBU output sections. The rugged output circuits feature transformer coupling.
For exibility, each of the eight outputs
can individually select input A or B as its
source. This allows the Model 85 to act as
a single 1x8 distribution amplier (DA), or
two fully independent DAs. Example con-
gurations include creating a dual 1x4 DA,
or a combination 1x3 DA and 1x5 DA.
Technical Background
The original AES/EBU specication
(AES3-1985) called for a single transmitter
to drive up to three receivers. In practice
this proved to make data transmission
susceptible to errors as an impedance
mismatch is created whenever more than
one receiver is driven. The revised edition
of the specication (AES3-1992) advises
that a single transmitter should drive only
a single receiver. The Model 85 addresses
this requirement in a simple, reliable manner. Up to eight identical, but fully isolated,
“copies” of the original source are created.
Single rack space mounting, standard
XLR-type connectors, and status LEDs
make installation of the Model 85 a simple
job. The AC mains input power is factory
congured for 100, 120, or 220/240 V
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No Data Manipulation
The Model 85 performs minimal processing to the AES/EBU digital audio data. The
signal is received, converted to a standard
logic signal, then retransmitted using rugged driver circuits. No timing “correction” is
performed. No data is manipulated, added,
or changed. The Model 85 assumes that
your digital signals have been carefully
created and simply need to be distributed
to multiple inputs. In an age when every-
one wants to “x” your digital signals the
Model 85 takes a “hands off” approach.
With a nominal 60 nanosecond input to
output delay, the outputs are essentially
identical to the inputs.
Installation
In this section you will be installing the
Model 85 in an equipment rack. AES/EBU
input and output connections will be made
using the ten XLR-type connectors located
on the back panel. AC mains power will be
connected to the Model 85.
System Components
The shipping carton contains a Model 85,
User Guide, and warranty card. Units destined for North America are shipped with
an AC mains cord. Your dealer or distributor will provide an AC mains cord for nonNorth American destinations.
Mounting the Model 85
The Model 85 requires one space in a
standard 19-inch (48.3 cm) equipment
rack. It is desirable to locate the Model 85
to allow easy access to both the front and
the back panels. The back panel contains
the input and output connectors. The front
Model 85 Front Panel
Power
present LED
present LEDs
Model 85 Back Panel
AC mains
connection
Signal
AES/EBU
outputs
Output source select
conguration switches
AES/EBU
inputs
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panel is used to access the output-select
switches. The front panel also contains
several LED indicators. The Model 85 is
secured to the equipment rack using two
mounting screws per side.
AES/EBU Inputs
The Model 85 provides two AES/EBU
inputs. Physically the inputs are located
on the back panel and use standard 3-pin
XLR-type female connectors. The source
signals will need to terminate on cables
with XLR-type male plugs to connect with
the inputs.
While it’s a good idea to always maintain
consistent cable polarity, the AES/EBU
specication clearly states that signal
polarity is not an issue. With this in mind
understand that identifying one of the pins
as “hot” or “high” is not really relevant.
For consistency the Model 85 does maintain input-to-output polarity. A low-to-high
transition on pin 2 of the input results in a
low-to-high transition on an output.
For best performance you should consider
AES/EBU signals to always be a balanced
(differential) signal. Pins 2 and 3 of the
XLR-type connectors should carry signal
and pin 1 is appropriate for shield. Never
strap pin 2 or pin 3 to pin 1—this might be
appropriate for unbalanced analog signals
but not for this fast-movin’ digital cat!
Beyond containing a shield appropriate for
digital signals, the exact cable choice is
up to you. There is an inverse relationship
between cable capacitance and maximum
allowable cable length. The AES/EBU
specication calls for a 100 meter maximum, but high performance cable should
allow a longer run.
Part of the Model 85's exibility is the fact
that each of the eight outputs can select
as its source either input A or input B. If
you’re using the unit strictly as a 1-input/
8-output device, only a connection to input
A is required. If some outputs have input A
as their source, and others have input B as
their source, then you’ll need signals connected to both inputs.
AES/EBU Outputs
The Model 85 contains eight independent
AES/EBU outputs. The signals are accessible on the back panel by means of eight
3-pin XLR-type male connectors. Your
cables will need to terminate on XLR-type
female connectors. The recommendations
made for the inputs also apply for the outputs: maintain polarity, wire for balanced
operation, and select, if appropriate, a lowcapacitance cable.
AC Mains Power
The Model 85 is internally congured
to operate from either 100, 120, or 220/
240 V, 50/60 Hz. In most cases, units
shipped to North America are factory
selected for 120 V operation. Units bound
for Japan are selected for 100 V, while
our friends “down under” and in Europe
receive units set for 220/240 V. Before
connecting the Model 85 to AC mains
power, check that it is congured to match
the local mains voltage. Look on the back
panel, adjacent to the power entry connec-
tor, for the congured voltage(s). Note than
an incorrect conguration could seriously
damage the unit. Should it be necessary to
change the unit’s operating voltage it must
be performed only at the factory or by an
authorized service technician.
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The Model 85 uses an IEC standard connector to mate with the AC mains cord.
The wire colors in the AC mains cord
should conform to the internationally recognized CEE color code and must
be wired accordingly:
Connection Wire Color
Neutral (N) Light Blue
Line (L) Brown
Protective Earth (E) Green/Yellow
Safety Warning: The Model 85 does
not contain an AC mains disconnect
switch. As such the mains cord plug
serves as the disconnection device.
Safety consideration requires that
the plug and associated outlet be
easily accessible to allow rapid disconnection of mains power should it prove
necessary.
sets its associated output channel for a
source of input A. A switch in the down
position selects input B. A small at-blade
screwdriver may be of assistance when
setting the switches.
Operation
Now that you’ve installed and congured
the system, you’re ready to go. You should
nd operation very easy; there is almost
nothing to do on a day-to-day basis. For
peace of mind, the signal present LEDs
will give you a visual indication whenever
signals are present on the Model 85’s
inputs. Note that the signal present LEDs
are not intended to provide an indication
that valid AES/EBU signals are present. They are provided as a handy macro
method of determining if signals are active
on the inputs.
As soon as AC mains power is connected,
the Model 85’s power present LED will
light. If a digital signal is active on an input
its associated signal present LED will light.
The unit is now ready for years of trusty
service!
Conguration
Output Source Selection
Each of the eight AES/EBU outputs is
individually congurable to have input A
or input B as its source. Eight DIP-type
switches, located on the right side of the
front panel, are used to select the source
for each output. The legend on the switches corresponds to the output channel numbers. A switch that is set to the up position
Each of the eight outputs is fully independent. You can patch, reconnect, or even
short out an interconnecting cable without
effecting the other outputs. Using the frontpanel DIP switches you can change the
output source of any or all of the outputs
whenever you wish.
Troubleshooting
If you’re having problems getting the
Model 85 up and running, this section can
help. If you haven’t read the other sections of this guide, you should do so before
proceeding.
If the Model 85 Doesn’t Work At All
A source of AC mains power must be
connected to the Model 85. Depending
on the version you have purchased, 100,
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120, or 220/240 Vac, 50/60 Hz is required.
Conrm what mains voltage is required by
observing the selection boxes to the left
of the AC mains connector on the back
panel. Whenever mains power is connected the power present LED should be
lit. If the LED is not lit conrm that the main
power source is active (“hot”) and that the
connector on the cord is securely mated
with the plug on the back panel.
For safety in the event of a major internal
failure or the connection of incorrect AC
mains voltage, the Model 85 contains a
fuse inside the cabinet. The fuse will open
(“blow”) if the failure of an internal component causes excessive current to be
drawn from the internal power supply. The
fuse will also open should 220/240 Vac be
connected to a Model 85 that is congured
for 100 or 120 Vac operation. The fuse is
intended to be replaced only by a qualied
service technician. This person will have
the training to safely access the “guts” of
the Model 85 and identify where a problem
is located.
If Signal Doesn’t Seem to Be Present
on the Outputs
Valid outputs depend on a valid input
source. Ensure that the signal present
LEDs are lit in response to what you consider valid input signals. Should a signal
present LED not be lit conrm that the
source is operating and the cabling has
been correctly prepared. On the front
panel, check the output source selection
switches to conrm the correct settings.
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Specications
AES/EBU Inputs: 2
Type: capacitor isolated, transformer coupled
Receiver Equalization: none
Impedance: 110 ohms, nominal
Amplitude Range: 0.3 to 7 Vp-p
AES/EBU Outputs: 8
Type: transformer coupled
Impedance: 110 ohms, nominal
Level: 3.0 Vp-p, terminated, nominal
Input-Output Time Delay: 60 nSec, nominal
AES/EBU Performance Compatibility: designed
for compliance with AES3-1992 (ANSI S4.40-
1992), AES Recommended practice for digital
audio engineering—Serial transmission format for
two-channel linearly represented digital audio data
LED Indicators: 3
Function: 1 power present, 2 signal present
Fusing: 1
Type: 5 x 20 mm time lag (Littelfuse 218-series or
equivalent)
Rating: 0.400 A for 100 and 120 V mains power,
0.200 A for 220/240 V mains power
Connectors:
AES/EBU: 3-pin XLR-type, female (2), male (8)
AC Mains: standard 3-blade plug, meets IEC 320
specications
AC Mains Requirement: 100, 120, or 220/240 V,
±10%, factory congured, 50/60 Hz, 100-120 V
0.4 A maximum, 220/240 V 0.2 A maximum
Dimensions (Overall):
19.00 inches wide (48.3 cm)
1.72 inches high (4.4 cm)
6.65 inches deep (16.9 cm)
Mounting: one space (1U) in a standard 19-inch
rack
Weight: 7.0 pounds (3.2 kg)
Specications and information contained in this
User Guide subject to change without notice.
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