Studio Technologies Model 374A Intercom Beltpack

Over a standard IP network, multiple Model 374A units can be used in party-line (PL) intercom applications with help from an external Dante-enabled audio matrix such as the Studio Technologies Model 5422 Dante Intercom Audio Engine. Or, units can be used "point-to-point" or interfaced with Dante-compatible matrix intercom systems.

Only a single Power-over-Ethernet (PoE) connection is required for operation. Key user features can be easily configured using the STcontroller software application. Configurable parametres include electret microphone powering, microphone preamplifier gain, talk button operation, and headphone channel assignment. User features include integrated sidetone, remote mic kill ("talk off"), and monitor-only modes. The wide range of capabilities, along with the excellent audio quality provided by the digital audio signal path, offers a unique and powerful user experience.

Set up and configuration of the Model 374A is simple. An etherCON^® RJ45 receptacle is used to interconnect with a standard twisted-pair Ethernet port associated with a local-area network (LAN). This connection provides both power and bidirectional digital audio. A broadcast or intercom-style stereo or monaural headset with a dynamic or electret (DC-powered) microphone interfaces with the unit using a 5-pin XLR connector.

The STcontroller software application is used to select the unit's operating parametres. Four talk pushbutton switches can be configured for optimal operation. Four push-in/push-out ("pop out") rotary controls make it easy to set and maintain the desired headphone output level. The Model 374A's enclosure is made from an aluminum alloy which offers both light weight and ruggedness. A stainless steel "belt clip," located on the back of the unit, allows direct attachment to a user's clothing.

The audio quality of the Model 374A's four audio channels is excellent, with low distortion, low noise, and high headroom. Careful circuit design and rugged components ensure long, reliable operation. A wide range of applications can be supported, including sports and entertainment TV and radio events, streaming broadcasts, corporate and government AV installations, and post-production facilities.

Dante Audio-over-Ethernet

Audio data is sent to and received from the Model 374A using the Dante audio-over-Ethernet media networking technology. As a Dante-compliant device, the Model 374A's four audio output (Dante transmitter) and four audio input (Dante receiver) channels can be interconnected (routed) with other devices using the Dante Controller software application. The Dante transmitter and receiver channels are limited to supporting four Dante flows, two in each direction. The digital audio's bit depth is up to 24 with a sampling rate of 48 kHz. The Model 374A is AES67 compatible and compliant with the Dante Domain Manager^™ software application.

Two bi-color LEDs provide an indication of the Dante connection status. The Dante Controller's Identify command takes on a unique role with the Model 374A. Not only will it cause the talk button LEDs to light in a unique highly visible sequence, it can also be configured to turn off any active talk channels.

Audio Quality

The Model 374A's completely "pro" performance is counter to the less-than-stellar reputation of typical party-line (PL) intercom audio. A low-noise, wide dynamic-range microphone preamplifier and associated voltage-controlled-amplifier (VCA) dynamics controller (compressor) ensures that microphone audio quality is preserved while minimizing the chance of signal overload. DC power to support electret microphones can be enabled if necessary. The output of the microphone preamp and compressor is routed to an analog-to-digital converter (ADC) section that supports a sampling rate of 48 kHz with a bit depth of up to 24. The audio signal, now in the digital domain, travels through the processor and on to the Dante interface section where it is packetized and prepared for transport over Ethernet.

Audio input signals arrive via four Dante receiver channels. The supported sampling rate is 48 kHz with a bit depth of up to 24. The audio signals pass into the Model 374A's processor where channel routing, headphone level control, and sidetone creation are performed within the digital domain. This provides flexibility, allowing for precise control of the audio signals and eliminates the need for the four rotary level controls from having to directly handle analog audio signals. The audio signals destined for the 2-channel headphone output are sent to a high-performance digital-to-analog converter and then on to robust driver circuitry. High signal levels can be provided to a variety of headsets, headphones, and earpieces.