Studio Technologies 212 2013 - Manual (Page 29)

Model 212 User Guide Issue 5, May 2013
Studio Technologies, Inc. Page 29
A qualified technician can easily revise the
LED colors to meet an application’s exact
needs. The process would begin by disas-
sembling the Model 212’s enclosure and
detaching the pushbutton/LED printed cir-
cuit board assembly. The LEDs would then
be unsoldered, removed, and reinstalled (or
replaced) in the desired locations. To control
the LED current and set the brightness, a
825 ohm 1206-size surface-mount resistor
is electrically in series with each LED.
For additional information about changing
the LED colors, please contact Studio
Technologies’ technical support.
Travel Case
For portable applications it may be desir-
able to store and transport each Model
212 in a protective case. After much travel
with prototype announcer console units,
Studio Technologies’ personnel learned to
appreciate the Pelican Model 1450 case.
Purchased with the foam interior option, it
does an excellent job of holding one Model
212, its associated 24 volt DC power sup-
ply, and documentation. Some applications
may benefit from selecting a larger case that
would also hold a related headset, cables,
etc. A larger case could also be selected
that would hold multiple Model 212 units.
Pelican sells their products through a dealer
network, many of which can be located via
a web search.
Connecting Analog Inputs
The Model 212 is designed to directly
connect with digital audio signals. However,
there may be applications where it would
be useful to also be able to connect analog
line-level audio sources. To facilitate this
one or two line input cards can be installed.
They are mounted into the spare connec-
tor locations that are provided on the Model
212’s back panel. Two types of line input
cards are available from Studio Technolo-
gies and are purchased separately. One
card contains passive circuitry, including
a 3-pin female XLR connector and a
10 k ohm to 10 k ohm isolation transformer.
Once installed, balanced or unbalanced
line-level audio sources can be directly
connected. The second type of card con-
tains an identical connector and isolation
transformer circuit, followed by a sophisti-
cated VCA-based limiter circuit. This
arrangement helps prevent abnormally
large signal levels from reaching the
headphone output channels.
Each line input card kit contains a printed
circuit board assembly, the required inter-
connecting cables, and hardware. To install
the kit is very simple. The XLR connector
is mounted into one of the spare connector
locations on the Model 212’s back panel.
This secures the connector and associated
printed circuit board to the enclosure. The
interconnecting cables are then used to link
the card with the Model 212’s auxiliary input
headers on the main printed circuit board
assembly.
For balanced audio sources the mating
connector (3-pin male XLR) should be
wired so that signal high (+ or hot) is con-
nected to pin 2, signal low (– or cold) is
connected to pin 3, and shield is connected
to pin 1. Unbalanced sources should be
wired so that signal high is on pin 2, and
signal low/shield is connected to both pins
1 and 3. If this results in hum on the input,
try connecting signal high to pin 2, signal
low/shield to pin 3, and pin 1 left untermi-
nated (“floating”).
Several things are worth mentioning when
it comes time to actually using a line input
card. The input is transformer coupled with