Studio Technologies 85 - Manual (Page 7)

Model 85 User Guide Issue 4, June 2011
Studio Technologies, Inc. Page 7
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
specification 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 main-
tain 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
specification calls for a 100 meter maxi-
mum, but high performance cable should
allow a longer run.
Part of the Model 85's flexibility 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 con-
nected to both inputs.
AES/EBU Outputs
The Model 85 contains eight independent
AES/EBU outputs. The signals are acces-
sible 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 out-
puts: maintain polarity, wire for balanced
operation, and select, if appropriate, a low-
capacitance cable.
AC Mains Power
The Model 85 is internally configured
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 configured to match
the local mains voltage. Look on the back
panel, adjacent to the power entry connec-
tor, for the configured voltage(s). Note than
an incorrect configuration 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.