Studio Technologies 230 2014 - Manual (Page 47)

Model 230 User Guide Issue 9, November 2014
Studio Technologies, Inc. Page 47
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 cases this may
reduce the microphone signal level by
less than one dB. Also, two 150 ohm resis-
tors are electrically connected in series
between the microphone input connector
and the direct microphone output connec-
tor. These resistors provide isolation, al-
lowing 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 oper-
ate. The series resistors will have minimal
impact, simply raising the microphone’s
apparent source impedance as “seen” by
the external preamplifier.
Pushbutton Backlighting
For special applications, provision has
been made to allow LED illumination
(“backlighting”) of the three pushbutton
switches. This may prove useful for appli-
cations where adequate room lighting
is not available. It can also serve in custom
Model 230 configurations. It’s important to
note that the button lighting is not intend-
ed to serve tally applications. It is strictly
intended to provide a moderate amount
of illumination of the button’s clear lens
and associated labeling.
From the factory, LED lamps are not
installed in the pushbutton housings. The
socket in each housing was designed for
inserting a pluggable T-1 bi-pin incandes-
cent type but we find that the more mod-
ern leaded T1 LEDs work very well. The
Model 230’s 5 volt DC power supply is
connected to the socket in each pushbut-
ton housing by way of 2.2 k (2200 ohm)
resistors. With this implementation, along
with the recommended LED, only 1 milli-
ampere per LED is consumed.
It’s intended that high-efficiency white
LEDs be installed. They use very little DC
current and have essentially infinite life.
The recommended LED is the Kingbright
WP7104QWC/D which as of the time of
this writing is available from sources
such as Digi-Key (www.digikey.com) and
Mouser Electronics (www. mouser.com).
The mating socket in each pushbutton as-
sembly is accessed by removing the but-
ton’s lens caps, graphic label, and back
frosted lens. Once this is done installing
the LED should be very simple, requiring
only lead trimming and careful insertion.
Begin by removing the top clear lens, la-
bel, and frosted under-lens in each push-
button. Trim the LED leads to 0.25 inches
in length and insert into the sockets with
the cathode end located nearest the front
of the Model 230. Power up the Model 230
and observe if the LEDs light. The LEDs
are polarity sensitive and if one or more of
them do not light, remove the offending
LED(s), rotate them 180 degrees, and then
re-insert.