Studio Technologies 230 2014 - Manual (Page 44)

Issue 9, November 2014 Model 230 User Guide
Page 44 Studio Technologies, Inc.
to allow the output of the compressor to
serve as the source. With these simple
provisions a qualified technician can move
the surface-mount resistor and achieve the
desired audio-source change. As the pro-
cess does require soldering and “board
level” component work, electing to make
the change must be approached with
care. Contact the factory for additional
details.
Additional Line-Level Output
The two talkback buttons on the Model
230 allow talkback audio to be routed to
one line-level output and one or two
channels associated with an intercom line.
However, there may be applications where
it would be helpful to have a second line-
level output. The Model 230 has made
provision to accomplish this using an
optional line output card. This card, avail-
able from Studio Technologies and pur-
chased separately (part number 31086), is
mounted into a spare connector location
located on the Model 230’s back panel.
Audio “drive” for the card comes from the
circuitry associated with the talkback-to-
intercom functions. Due to this circuitry’s
design, the nominal output level of the line
output card is –10 dBu. Two 3-position
header connectors, located on the Model
230’s main printed circuit board assembly,
provide access to talkback-to-intercom
channel 1 and channel 2 audio signals.
The line output card contains passive
circuitry, including a 3-pin male XLR con-
nector and a 600 ohm to 600 ohm isola-
tion transformer. Capacitors in series with
the transformer’s output provide protec-
tion against damage in case DC power is
present on a connected cable. In series
with the output are 300 ohm resistors,
making the effective output impedance
approximately 600 ohms. These resistors
can be used to create a passive summing
network.
A line output card kit contains a printed
circuit board assembly, an interconnecting
cable, and hardware. Installing the kit is
very simple. The 3-pin male XLR connec-
tor is mounted in one of the spare con-
nector locations on the Model 230’s back
panel. This secures the connector and
associated printed circuit board to the en-
closure. The interconnecting cable is then
used to link the card and the Model 230’s
main printed circuit board assembly. One
end of the cable is plugged into the card’s
3-position “header” that is labeled IN. The
other end of the cable is plugged into the
desired 3-position header located on the
main printed circuit board assembly. The
header associated with talkback-to-inter-
com channel 1 is labeled P14. The header
associated with talkback-to-intercom
channel 2 is labeled P13.
Note that the unused header remaining on
the line output card has its pins “multed”
with the leads on the 3-pin male XLR con-
nector. It is provided for other applications
that may need it. Additional installation
details are provided in the Additional
Connectors section of the user guide.
A recommended connector labeling
method is also included.
Interface cables intended for connection
to balanced loads should be wired so that
signal high (+ or hot) is connected to pin
2, signal low (– or cold) is connected to
pin 3, and shield is connected to pin 1.
For unbalanced loads the connector
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
or noise, try connecting signal high to