Studio Technologies 230 2008 - Manual (Page 49)

Model 230 User Guide Issue 7, October 2008
Studio Technologies, Inc. Page 49
The line output card contains passive
circuitry, including a 3-pin male XLR-type
connector and a 600 ohm to 600 ohm
isolation transformer. Capacitors in series
with the transformer’s output provide pro-
tection 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 interconnect-
ing cable, and hardware. Installing the kit
is very simple. The 3-pin male XLR-type
connector is mounted in one of the spare
connector locations on the Model 230’s
back panel. This secures the connector
and associated printed circuit board to the
enclosure. 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 assem-
bly. The header associated with talkback-
to-intercom 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 “mult-
ed” with the leads on the 3-pin male XLR-
type connector. 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 label-
ing 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
pin 2, signal low/shield to pin 3, and
leave pin 1 left unterminated (“floating”).
Several things are worth mentioning. As
previously discussed, the nominal output
level of this additional line-level talkback
output is –10 dBu. This is significantly less
than the nominal level of the Model 230’s
line-level talkback output. The audio qual-
ity is similar, only the level is different. Also
note that if a line output card is installed
its output, as well as its associated talk-
back-to-intercom channel, will always
operate in tandem. Independent control
is not possible, nor should it be required.
Direct Microphone Output
The Model 230’s main output is intended
to be used as the on-air, stadium an-
nouncement, or other primary audio feed.
The path from the unit’s microphone input
connector to the main output connector is
by way of active circuitry. A low noise, low
distortion microphone preamplifier stage,
“clickless” audio switching, and a high-
quality transformer-coupled output circuit
work together in achieving excellent per-
formance. The nominal level of the main
output is –2 dBu, allowing interconnection
with related devices at a near-standard
“line” level. However, there may be appli-
cations where an output that directly
relates to the connected microphone
would be beneficial. The Model 230 has