Studio Technologies 220 2004 - Manual (Page 37)

Issue 2, August 2004 Model 220 User Guide
Page 38 Studio Technologies, Inc.
relay operates under software control,
following the configuration selected using
two of the DIP-type switches. Four operat-
ing modes are available: relay disabled,
relay follows main output status, relay
follows talkback output 1 button status,
and relay follows talkback output 2 but-
ton status. These choices were previously
discussed in this user guide and should
be reviewed.
The relay provides two “form-C” contacts,
each consisting of a common, normally
open (not shorted), and normally closed
(shorted) connection. Obviously the two
form-C contacts change state in unison;
two independent relay functions are
not provided. These relay contacts are
accessible on the Model 220’s main
printed circuit board assembly by way of
3-position header connectors. The con-
tacts are titled A and B, but there is no
significance between the two. The header
labeled P10 provides access to auxiliary
relay contact A. Header P9 provides ac-
cess to auxiliary relay contact B. With both
headers pin 1 is normally closed, pin 2 is
common, and pin 3 is normally open. For
additional details on connecting to the 3-
position headers please refer to the Addi-
tional Connectors section in the Technical
Notes area of this user guide.
Direct Microphone Output
The Model 220’s main output is intended
to be used as the on-air, stadium
announcement, or other primary audio
feed. The path from the unit’s microphone
input connector to the main output con-
nector is by way of active circuitry. A low
noise, low distortion microphone pream-
plifier stage, “clickless” audio switching,
and a high-quality transformer-coupled
output circuit work together in achieving
excellent performance. 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 applications where an output that
directly relates to the connected micro-
phone would be beneficial. The Model 220
has made provision to accomplish this by
using the optional direct microphone out-
put card. This card, available from Studio
Technologies and purchased separately
(part number 31058), is mounted in a
spare connector location available on the
Model 220’s back panel. With this addi-
tion both an “active” main output and a
“passive” direct microphone output will be
available. Of course, both outputs provide
quiet noise-free on/off (“muting”) control.
The primary application for the direct
microphone output is when the Model 220
is integrated into a system that includes
a high-performance microphone pream-
plifier. This preamplifier may be part of a
stand-alone voice-processor unit, or a
microphone input associated with an
audio console. Engineering personnel
may prefer the sonic characteristics of the
external microphone preamp over that of
the one integrated into the Model 220.
It’s important to note that the direct mi-
crophone output card provides a direct
“metallic” path from the microphone input
to the external preamplifier circuitry. It is
not simply an audio “pad” (attenuator) that
reduces the level of the main output from
“line” to “mic.” The Model 220’s auxiliary
relay contacts, along with circuitry on the
direct microphone output card, provide
click-free muting of the signal.
The direct microphone output card con-
tains only passive circuitry. A 3-pin male
XLR-type connector is provided for the
output signal. A resistor and large electro-
lytic capacitor form the muting circuit. This