Features 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 750's 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 750's 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 vehicle's 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.
Downloads Model 750 Data Sheet
Model 750 User Guide
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