Fostex 750 manual System Features

Model 750

System Features

Mic/Line Inputs

Four transformer-coupled input channels are provided for connection to micro- phone or line-level signals. The circuitry is “ruggedized” for reliability under tough operating conditions. A full set of features is provided for each input channel, includ- ing selectable input sensitivity, +48V phantom power, low-cut filter, phase reverse, level control, and pan pot. For operator assistance, a bi-color LED pro- vides signal present and peak level indica- tion. Two illuminated push-button 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 signals to the main and AUX audio buses.

Main Output

Signals from the mic/line input channels, stereo line input channels, and the setup section (discussed later) combine to

create the main audio output. The main output bus is stereo, but can be used to create two independent monaural audio mixes. Two studio-quality, stereo limiter/ compressor circuits are provided to con- trol the dynamic range of the main audio bus. Far from a simple “clipper,” each limiter/compressor circuit utilizes a sophis- ticated laser-trimmed voltage-controlled amplifier (VCA) integrated circuit for quiet, low-distortion operation. For installation flexibility, three sets of stereo output cir- cuitry provide access to the main stereo bus: two are electronically balanced, line- level; the third is transformer-balanced, with its output level selectable for mic or line.

AUX Output

The Model 750 provides a second stereo audio bus that can be configured to oper- ate 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

asecond stereo output 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. 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 operators will find this function ex- tremely useful, enabling one or more of the input channels, or the setup section, to be monitored without interfering with signals assigned to the main output bus. Two DIP switches, accessible from the

Issue 3, May 1997	Model 750 User Guide
Page 8	Studio Technologies, Inc.