Studio Technologies 220 2008 - Manual (Page 39)

Model 220 User Guide Issue 4, October 2008
Studio Technologies, Inc. Page 39
printed circuit board assembly. One end
of the first interconnecting cable is
plugged into the card’s 3-position header
that is labeled IN. The other end of this
cable is plugged into the 3-position head-
er associated with the microphone input
connector, labeled P5, located on the
main printed circuit board assembly. One
end of the second interconnecting cable
is plugged into the card’s header that is
labeled RELAY. The other end of this cable
is plugged into the header associated with
the auxiliary relay, labeled P9, located on
the main printed circuit board. Additional
installation details are provided in the
Additional Connectors section of the user
guide. A recommended connector label-
ing method is also included.
After the direct microphone output card
has been installed, one configuration step
must also be performed. Using the con-
figuration switches, located on the bottom
of the Model 220’s enclosure, the auxiliary
relay control mode must be set to the
“follows main output status” position. This
provides the on/off (muting) control of the
direct microphone output signal. Should
the auxiliary relay’s configuration be left
in the “relay disabled” position, the direct
microphone output will always be in the
off (muted) state. It’s interesting to note
that the recommended auxiliary relay
configuration assumes that the direct
microphone output will be used in place
of the Model 220’s main output. However,
for other applications there is certainly no
reason why the direct microphone output
can’t be configured to follow the status of
one of the talkback buttons. Special situ-
ations may benefit from having a micro-
phone signal that is active only during
“talkback.”
Using the direct microphone output is
essentially the same as connecting di-
rectly to a microphone. An interface cable
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. When connecting a
condenser microphone it’s recommended
that the Model 220 provide the source of
phantom power. In this way the micro-
phone will stay active whenever the Model
220 is operating, even if the connection
made to the direct microphone output is
broken. By ensuring that the microphone
remains active, the talkback functions will
continue to operate correctly.
Several slight differences between con-
necting to a stand-alone microphone
and connecting to the Model 220’s direct
microphone output should be noted. The
first is that pin 1 on the direct microphone
output is electrically connected to pin 1 on
the Model 220’s microphone input con-
nector, as well as the Model 220’s signal
common/chassis connection. This is
required so that the Model 220’s phantom
power circuit can function and that proper
microphone-cable shielding can be pro-
vided. It’s not expected that this will cause
any problems.
Also, while the circuitry between the mi-
crophone input and direct microphone
output is entirely passive, it will still impact
the microphone signal. The impact is be-
nign but is still worthy of description. The
circuitry associated with the Model 220’s
microphone preamplifier and phantom
power supply is always connected across
(“bridged onto”) the microphone input.
This adds a 2 k ohm essentially resistive
load to the microphone, something that
should have no sonic impact. In some