Studio Technologies 220 2008 - Manual (Page 9)

Model 220 User Guide Issue 4, October 2008
Studio Technologies, Inc. Page 9
output circuits act as voltage, rather than
power, drivers. In this configuration they
can provide high output levels with very
low distortion and noise, along with mini-
mal current consumption. The output cir-
cuits are configured to safely drive stereo
or mono loads. This ensures that all types
of headphones, headsets, and earpieces
can be directly connected.
Audio Quality and Protection
The Model 220’s circuitry is carefully
tailored to provide excellent audio perfor-
mance. Professional-quality components
are featured throughout. For reliability all
audio routing is performed using solid-
state devices. In all critical audio paths,
“clickless” electronic switches provide
noise-free control. All audio inputs and
outputs make extensive use of protection
components. This limits the chance of
damage from ESD and other undesirable,
yet real-world, hazards.
Power Sources
The Model 220 can derive its operating
power from either the IFB input or an
external nominal 24 volt DC source. For
redundancy, both power sources can be
connected simultaneously. An internal
switch-mode power supply ensures that
all Model 220 features, including phantom
power, are available when the unit is
powered by either source.
The Model 220 is compatible with IFB
circuits provided by most standard broad-
cast systems. However, maximum perfor-
mance can often be obtained by using
the IFB interface devices available from
Studio Technologies. Single-channel and
four-channel units are available, each
providing high-quality audio along with
an excellent source of DC power. They’re
directly compatible with most matrix inter-
com systems, as well as standard line-
level audio signals. Refer to the Studio
Technologies website for details.
Auxiliary Relay
The Model 220’s circuitry includes a
general-purpose relay, allowing special-
ized configurations to be created. Un-
der software control, the relay can be
configured to follow the state of the mic,
talkback 1, or talkback 2 buttons. Taking
advantage of the locations provided for
additional XLR-type connectors, a techni-
cian may easily implement a variety of
functions such as mic active indication,
audio muting during talkback, or audio
insertion control. Several modes were
specifically included to allow direct control
of the relay using the talkback 2 button,
without impacting any of the audio sig-
nals. The auxiliary relay is also used by the
optional direct microphone output card.
Configuration
Model 220 configurations are made using
a number of DIP-type switches and two
trim potentiometers. One 8-position switch
array is used to set the gain of the micro-
phone preamplifier and the on/off status
of phantom power. Another 8-position
switch array configures which of the cue
audio sources are routed to the head-
phone output. Two additional 8-position
switch arrays communicate the desired
operating modes to the microprocessor.
Two rotary trim pots are used to adjust
the input sensitivity of the line inputs. All
switches and trim pots are accessible
via the bottom of the Model 220’s enclo-
sure; the unit does not have to be disas-
sembled. Changes made to any of the
configuration parameters become active
immediately. To prevent access to the