Studio Technologies 220 2008 - Manual (Page 38)

Issue 4, October 2008 Model 220 User Guide
Page 38 Studio Technologies, Inc.
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 Additional 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
microphone 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 arrangement allows muting to take
place without disturbing phantom power
that may be enabled to support a con-
denser-type microphone. The direct mi-
crophone output card also contacts two
3-position header connectors. These
interface with “headers” on the Model
220’s main printed circuit board assembly,
providing access to the microphone input
connector and auxiliary relay contact.
The direct microphone output card kit
contains a printed circuit board assembly,
two interconnecting cables, and mounting
hardware. Installing the kit is very simple.
The card’s 3-pin male XLR-type connec-
tor is mounted into one of the three spare
connector locations on the Model 220’s
back panel. Specifically, the connector
location that is closest to the microphone
input connector should be used. The two
screws, with associated locking nuts, are
used to secure the connector and associ-
ated printed circuit board to the enclosure.
The interconnecting cables are then used
to link the card with the Model 220’s main