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Highlights
Four mic/line inputs
Two
stereo line inputs
Extensive
monitor section
Main and
AUX stereo audio buses
Studio-quality limiter/compressors
Three
isolated main output connections
Separate
speaker and headphone outputs
Setup
section, including voice record/playback and tone generation
VU meters
with peak LEDs
All operator controls on front panel
Two
rack-space mounting
Mic/Line
Inputs
Four
transformer-coupled input channels are provided for connection to
microphone or line-level signals. A full set of features is provided for
each input channel, including selectable input sensitivity, +48 V phantom
power, low-cut filter, phase reverse, level control, and pan pot. For
operator assistance, a bi-color LED provides signal present and peak
indication. Two illuminated pushbutton switches control the routing of
the input signal to the main and auxiliary (AUX) audio buses. For
convenience, the four mic/line input sensitivity buttons, like all the
Model 750s operator controls, are located on the front panel.
Stereo Line
Inputs
Two
stereo line-level input channels are provided, and are intended for
connection with audio signals associated with video playback. The channels
support "real world" broadcast applications, where left and
right signals may, or may not, be an actual stereo pair. Routing buttons
allow each left and right input to be assigned to the left output bus, to
the right output bus, to both output buses, or muted. A level control,
along with a bi-color signal present/peak LED, supports each left and
right input. Two illuminated buttons control the routing of the input
signals to the output buses.
Main Audio Bus
Signals
from the mic/line input channels, stereo line input channels, and the
setup section combine to create the main audio bus. The main bus is
stereo, but can be used to create two independent monaural audio mixes.
Studio-quality, stereo limiter/compressors are provided to control the
dynamic range of the main bus. Far from a simple "clipper," each
limiter/compressor circuit utilizes a sophisticated laser-trimmed
voltage-controlled amplifier (VCA) integrated circuit for quiet,
low-distortion level control. For installation flexibility, three sets of
stereo output circuits provide access to the main bus: two are
electronically balanced, line-level; the third is transformer-balanced,
with a selectable mic or line output level.
AUX Audio Bus
The
Model 750 provides a second stereo bus that can be configured to operate
in either of two modes: as an auxiliary (AUX) output or as a monitor
interrupt function. In the AUX output mode special applications are easily
supported, such as creating a "mix-minus" feed or serving as a
second stereo output bus for on-air use. Signals from the mic/line input
channels, stereo line input channels, and the setup section can be
assigned to the AUX bus. Direct access to the AUX bus is provided by means
of an electronically balanced, line-level output.
In
most cases, however, the AUX interrupt mode will be selected, allowing the
normal monitor source to be interrupted and the AUX signal monitored in
its place. Model 750 users will find this function extremely useful,
enabling one or more of the input channels to be monitored without
interfering with signals assigned to the main output bus. Two DIP
switches, accessible from the front panel, allow the interrupt function to
be configured. One switch selects whether the monitor speaker output will
be interrupted by the AUX signal, the other whether the headphone output
will be interrupted.
Configurable
Outputs
Four
monaural, balanced, line-level outputs can serve in a wide range of
installation-specific applications. DIP switches, located on the back
panel, are used to select from the five available signal sources: main
audio bus left and right, AUX audio bus left and right, and mic/line input
channel direct. The switches can be set to create a number of resources,
including: additional stereo outputs, monaural outputs from the main or
AUX audio buses, or direct outputs from the mic/line input channels.
Monitor Section
Reminiscent
of much larger audio consoles, the Model 750s monitor section gives the
operator an extensive set of resources. Separate stereo outputs and level
controls are provided for connection to a monitor amplifier and
headphones. In addition to monitoring the main and AUX audio buses,
provision has been made for monitoring two external audio sources. These
stereo inputs are intended to be connected to off-air, microwave, or
satellite receivers. External Monitor Input 1 is compatible with
"+4" signals, while External Monitor Input 2 can be set, using a
front-panel DIP switch, for "10" or "+4"
compatibility.
Multiple
sources can be simultaneously selected for monitoring. This can prove
useful by allowing, for example, an operator to simultaneously monitor a
local mix and an externally provided mix-minus signal. A mono function
allows the monitored audio source to be checked for phase cancellation
problems and acceptable "sum-to-monaural" performance.
The
AUX interrupt mode allows monitoring of selected input channels and the
setup section without interfering with normal operation of the main audio
bus. For operator assistance, the meters can be configured to monitor the
AUX bus whenever it is active.
The
mechanical VU-type meters, along with peak level LED indicators, provide a
"user-friendly" indication of audio-signal levels. Fanatics for
addressing the details, Studio Technologies has even eliminated the issue
of burned-out meter-scale illumination by implementing a solid-state,
LED-based lighting scheme.
Setup
Section
Unique
to the Model 750 are the features provided by the setup section, the
highlight being the ability of the operator to record and play back three
voice identification segments. The Left+Right segment allows a voice
message of up to 12 seconds in length to be recorded, with playback going
to the left and right output channels. The Left Only and Right Only
segments allow recording of up to 4 seconds each, with playback going only
to their respective channels. The voice segments can prove useful,
allowing the facilities that receive the vehicles signal (generally
provided by microwave or satellite links) to quickly "learn"
more about the origin of the transmission. Information such as vehicle
identity, physical location, the names of technical and on-air personnel,
mobile telephone numbers, and left and right channel identifiers can
easily be sent. The voice audio source is selectable, being either an
internal microphone or an externally connected signal.
The
setup section also contains a digitally controlled sine-wave generator
which, under software control, produces a "0-level" single-tone
reference or multi-tone sequences. The single-tone output is selectable
for either 400 Hz or 1 kHzthe two industry-standard frequencies. The tone
sequences allow frequency response testing of a transmission chain, with
the choice of either a basic or an advanced sequence. In the basic setting
a 1 kHz "0-level" reference is generated, followed by individual
10 kHz, 1 kHz, and 100 Hz tones. In the advanced setting a 1 kHz reference is
generated, followed by 14 individual tones, ranging from 15 kHz to 50 Hz.
While
the voice and tone setup signals can be assigned to the main and AUX audio
buses, a direct line-level stereo output is also provided. This allows the
generation of setup and test signals without interfering with normal audio
mixer operation.
Talk
Back
The
Model 750 includes a talk back function. Two pushbutton switches allow
the selected voice source to be routed to the setup direct output and/or
the main and AUX audio buses.
Installation
While
the Model 750 is loaded with features, it only requires two spaces in a
standard 19-inch rack. Neutrik XLR-type and Ό-inch, 3-conductor audio
connectors are used for audio interconnections. Mains power is factory
configured for 100, 120, or 220/240 V, 50/60 Hz.
Model 750 Specifications
General
Audio Parameters:
Frequency Response: 20 Hz-20 kHz, ±0.5 dB, stereo line in/main out 1
Distortion (THD+N): 0.04%, measured at 1 kHz, mic in/main out 3
S/N Ratio: 80 dB, referenced to +4 dBu, mic in/main out 3
Connectors:
Mic/Line, Stereo Line, Main Out 3: 3-pin XLR-type (pin 2 high)
All Other Audio: Ό-inch, 3-conductor phone jacks
AC Mains: 3-blade IEC-type
Mic/Line
Inputs: 4
Type: balanced, transformer-coupled
Level Range: selectable for mic or line level
Microphone Power: +48 V phantom-type
Low-Cut Filter: 3 dB at 85Hz, 18 dB/octave slope
Status LED: bi-color, signal present/peak
Pan Type: constant energy
Pan Attenuation: 60 dB, nominal
Stereo
Line Inputs: 2
Type: electronically balanced
Nominal Level: +4 dBu (8 to +10 dBu acceptable)
Status LED: 2, bi-color, signal present/peak
Main
Audio Bus Limiter/Compressor: 2
Threshold: +10 dBu (6 dB above nominal output level)
Attack Time: 2 mSec, nominal
Release Time: 100 mSec, nominal
Slope: 5:1, nominal
Outputs
Main 1, Main 2, AUX, Configurable, and Setup Direct:
Type: electronically balanced, compatible with balanced or unbalanced
loads
Nominal Level: +4 dBu
Maximum Level: +27 dBu into 10 k ohms, +26 dBu into 600 ohms
Main
Output 3:
Type: balanced, transformer-coupled
Nominal Level: mic 36, line +4 dBu, selectable
Maximum Level: +22 dBu into 10 k ohms
Monitor
Output:
Type: electronically balanced, compatible with balanced or unbalanced
loads
Nominal Level: 2 dBu
Maximum Level: +21 dBu into 10 k ohms, +20 dBu into 600 ohms
Headphone
Output:
Compatibility: intended for connection to headphones with impedance of 100
ohms or greater
Maximum Output Voltage: 8 Vpp, 100 ohm load
External
Monitor Inputs:
Quantity: 2, stereo
Type: electronically balanced
Nominal Level, Input 1: +4 dBu
Nominal Level, Input 2: 10 or +4 dBu, selectable
Setup
Section:
Record L+R Duration: 12 seconds, maximum
Record L Only, R Only Duration: 4 seconds, maximum
Record Audio Source: internal microphone or external line level,
selectable
Single Tone Frequency: 400 Hz or 1 kHz, selectable
Basic Multi-Tone Frequencies: 1 kHz reference, followed by 10 kHz, 1 kHz,
100 Hz
Advanced Multi-Tone Frequencies: 1 kHz reference, followed by 14 tones
(15 kHz-50 Hz)
Setup Direct Output Level: +4 dBu, nominal,
adjustable, range 2 to +10 dBu
Talk
Back: connects voice audio source to setup direct and/or main and
AUX outputs
Record/Talk
Back External Audio Input:
Type: electronically balanced
Level Range: 20 to +4 dBu, adjustable
Metering:
2
Type: analog panel, VU scale, with signal peak LED
Calibration: 0 VU = +4 dBu, nominal, adjustable, range 2 to +10 dBu
AC
Mains Requirement: 100, 120, or 220/240 V, ±10%, factory
configured, 50/60 Hz, 40 watts maximum
Dimensions
(Overall):
19.00 inches wide (48.3 cm)
3.49 inches high (8.9 cm)
9.50 inches deep (21.4 cm)
Mounting:
two spaces in a standard 19-inch rack
Weight:
14.0 pounds (6.4 kg)
Specifications
subject to change without notice.
Audio Mixers
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