Studio Technologies 43 User Manual

User Guide
Issue 1, July 2004
This User Guide is applicable for serial numbers:
M43-00151 and later
Copyright © 2004 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50020-0704, Issue 1
Table of Contents
Introduction ................................................................... 5
Setup ............................................................................. 7
Operation ...................................................................... 10
Troubleshooting ............................................................ 10
Technical Notes ............................................................. 12
Specifications ................................................................ 14
Appendix A .................................................................... 16
Block Diagram
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Introduction
The Model 43 is designed to create a broadcast-standard IFB circuit from two line-level audio sources. The unit will find use in on-air and production broadcast applications, as well as specialized applica­tions such as post-production, recording studio, and equipment test and mainte­nance. The Model 43 is a unique and ver­satile product, providing the resources to easily create a high-performance “wet” IFB circuit in a compact, easy-to-use package.
The Model 43’s audio inputs are compatible with standard line-level audio sources, in­cluding analog outputs associated with digi­tal matrix intercom systems. The unit’s IFB circuit provides DC power and two analog audio signals to support a range of IFB user devices. The audio quality is excellent—little hiss, hum, or other artifacts are present. The Model 43 is housed in a rugged aluminum enclosure, making it suitable for permanent or temporary applications. All inputs and outputs interface using industry-standard 3-pin male and female XLR-type connec­tors. The connectors are manufactured by Neutrik® and feature gold-paled contacts and metal housings. A source of 24 volts DC is required for operation. Included with each unit is an external wall-mount 24 volt DC power source.
View showing left and right audio inputs
There may be persons not familiar with the term IFB. That’s not unreasonable as it’s a somewhat obscure acronym for inter­rupted foldback. (It can also be known as interruptible foldback.) On its own, the term “foldback” is an alternate way of de­scribing a cue or monitor function. Adding “interrupted” before it means that the cue source can be temporarily replaced with an audio signal originating from a pro­ducer, director, or other production per­sonnel. IFB circuits are often used in the broadcast industry for talent cueing appli­cations, in both studio and field settings. Both “dry” and “wet” IFB circuits can be deployed and their characteristics are worth reviewing. The term “dry” IFB typi­cally refers to a transformer-balanced line­level audio circuit with a +4 dBu nominal level. This is essentially a standard audio circuit that is commonly used to intercon­nect audio equipment. The term “wet” IFB refers to a circuit that combines DC power and one or two channels of analog audio. The audio is unbalanced with a typical nominal level of –10 dBu. A wet IFB circuit is the type implemented by the Model 43. As such, in this user guide the term IFB will always indicate a wet circuit.
IFB circuits provide an effective means
View showing 24 volt DC input and IFB circuit connections
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of delivering power and two channels
of audio to user devices by means of stan­dard audio cables. These cables, ubiqui­tous to the audio industry, interface using 3-pin male and female XLR-type connec­tors. With IFB circuits and standard audio cables it’s a simple matter to support user devices such as listen-only belt packs and announcer’s consoles with no external power source required. Whether the dis­tance from the source to the user device is 100 or 1000 feet, reliable operation can be provided.
In many cases, the Model 43 Interface will be used in on-air television applications. No matter if a unit is installed in a fixed location or as part of a remote facility, excellent performance can be obtained. In addition, the Model 43 is applicable for non-broadcast applications. For example, audio recording and post-production facilities can also effectively use the unit. Combined with stereo or mono listen­only belt packs, also available from Studio Technologies, a variety of headphone cue systems can easily be deployed. Maintenance facilities and test benches will appreciate having a Model 43 avail­able to provide assistance during the testing and repair of IFB user devices. As the unit’s audio inputs are compatible with standard line-level audio signals virtually any analog source can be connected.
from matrix intercom systems. If this is the case, two sources are typically designated to feed user cue signals to stereo or mon­aural headsets or headphones. Generally one source is configured in the matrix intercom system as “interrupt” while the other is configured as “program.” An al­ternate term often used for the “interrupt” channel is “program-with-interrupt.” This may be more descriptive as the function is actually a program source that gets interrupted with talkback audio. The “pro­gram” channel is typically a continuous source of program audio. An alternate term is “program-only.” For other applica­tions the Model 43’s audio inputs can be connected to one or two monaural sources, or alternately, to a stereo audio source. This configuration may prove use­ful in radio broadcasting, audio-with-pic­ture, or recording studio applications.
Maintaining excellent audio performance was a major Model 43 design goal—the hiss, hum, and noise associated with typical IFB circuits was simply not accept­able. The Model 43 meets those require­ments with audio that is “on-air” quality: low distortion, high signal-to-noise ratio, and ample headroom. On-air talent and guests, production personnel, and techni­cians will all appreciate the clean, quiet cue signal.
IFB Circuit
The Model 43 supplies one circuit that incorporates two audio inputs and a “wet” IFB output. The audio inputs are transformer coupled, have a nominal level of +4 dBu, and are compatible with balanced or unbalanced sources. In on­air television broadcast applications the audio sources will often be analog outputs
43’s IFB circuit provides DC power and two channels of unbalanced audio over a single 3-conductor output. The DC out­put is nominally 30 volts with a maximum rated current of 200 milliamperes. A major strength of the Model 43 is the IFB circuit’s ability to effectively deliver DC power over a variety of conditions. Unlike other inter­face devices that use a common but less­than-ideal circuit topology, a unique IFB
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As previously covered briefly, the Model
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