Studio Technologies MODEL-750
Audio Mixer, 2RU

MODEL-750

Model 750 is a high-performance audio mixer designed for use in ENG, SNG, and specialized broadcast applications. 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.

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.

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.

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.

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.

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
• Talk back function
• All operator controls on front panel
• Two rack-space mounting

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: ¼-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)

Our Part #  MODEL-750