Studio Technologies 230 2008 - Manual (Page 51)

Model 230 User Guide Issue 7, October 2008
Studio Technologies, Inc. Page 51
“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 230’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 230 provide the source of
phantom power. In this way the micro-
phone will stay active whenever the Model
230 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 230’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 230’s microphone input
connector, as well as the Model 230’s sig-
nal common/chassis connection. This is
required so that the Model 230’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
microphone input and direct microphone
output is entirely passive, it will still impact
the microphone signal. The impact is
benign but is still worthy of description.
The circuitry associated with the Model
230’s microphone preamplifier and phan-
tom power supply is always connected
across (“bridged onto”) the microphone
input. This adds a 2 k ohm essentially
resistive load to the microphone, some-
thing that should have no sonic impact.
In some case it may possibly reduce the
microphone signal level by less than one
dB. Two 150 ohm resistors are electrically
connected in series between the micro-
phone input connector and the direct
microphone output connector. These
resistors provide isolation, allowing the
direct microphone output to be muted
while still maintaining microphone audio
on the Model 230’s preamplifier input. This
audio is necessary so that the talkback
functions can continue to operate. The
series resistors will have minimal impact,
simply raising the microphone’s apparent
source impedance as “seen” by the exter-
nal preamplifier.