Studio Technologies Model 381 – On-Air Beltpack Studio Technologies

The Model 381 On-Air Beltpack offers a unique combination of audio resources to directly support a complete broadcast “stand-up” on-air position. Using Dante® audio-over-Ethernet technology, the unit provides main and talkback output channels, talent cue (IFB) input, and sidetone capabilities, as well as essential user controls in a compact, portable package. The Model 381 is compatible with the Dante Domain Manager™ (DDM) software application and is AES67-compliant for direct integration into many contemporary networked audio applications.

Features:

• Dante audio-over-Ethernet technology
• Creates complete “stand-up” on-air position
• One main and one talkback output channel
• Highly-flexible 2-channel headphone output
• Integrated sidetone function
• Excellent audio quality
• Uses STcontroller for configuration
• Power-over-Ethernet (PoE) powered

Introduction
Optimized for broadcast sports and live entertainment events, eSports, news-gathering, and streaming broadcast applications, the Model 381 allows incredibly simple deployment while maintaining “pro” audio quality and an intuitive user experience. With just a Power-over-Ethernet (PoE) connection, a dynamic or phantom-powered microphone, and a pair of headphones or an earpiece, the unit will be ready for “on-air” deployment. The STcontroller software application is used for configuring operating parameters including microphone preamplifier gain, P48 phantom power, headphone signal routing, sidetone operation, and talkback button action. The Model 381’s audio quality is excellent, with low distortion, low noise, and high headroom. Careful circuit design and rugged components ensure long, reliable operation.

Applications
The Model 381 provides an “all-Dante” solution for one on-air talent location. Two Dante audio input channels supply the user with their talent cue (IFB) signals. Should the cue signal be “mix-minus” an integrated sidetone function can provide the user with a microphone confidence signal. Two Dante audio output channels, one designated as main (for “on-air” use) and the other talkback, are routed via the associated local-area network (LAN) to inputs on Dante-compatible devices. A pushbutton switch, located on the Model 381’s top panel, provides a combination talkback and “cough” function. When talkback is not active audio associated with the microphone preamplifier is routed to the Dante main output channel; the Dante talkback output channel is muted. When the talkback function is active audio is muted on the Dante main output channel and activated on the Dante talkback output channel. The audio switching is performed in the digital domain and is virtually “click-free.”

Setup and Operation
Set up and operation of the Model 381 is simple. An etherCON® RJ45 jack is used to interconnect with a standard twisted-pair Ethernet port associated with a PoE-enabled network switch. This connection provides both power and bidirectional digital audio. A broadcast headset or handheld (“stick”) microphone can be directly connected to the unit’s 3-pin XLR microphone input connector. This input is compatible with dynamic or condenser microphones. An integrated P48 phantom power source can be enabled if desired. Stereo headphones, the headphone connections from a stereo or monaural headset, or even a monaural earpiece are connected to the headphone output jack. Two “push-in/push-out” rotary controls (potentiometers or “pots”) make it easy to set the level of the talent cue signals level being sent to the 2-channel headphone output.

The STcontroller software application is used to configure the wide range of Model 381 operating parameters. This allows the unit’s performance to be optimized to meet the needs of specific applications. The Model 381’s ultra-compact 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 top surface is curved to minimize the chance of the unit interfering with clothing or being readily observable “on camera.”

Ethernet Data and PoE
The Model 381 connects to a local area network (LAN) by way of a standard 100 Mb/s twisted-pair Ethernet interface. The physical 100BASE-TX interconnection is made by way of a Neutrik® etherCON RJ45 connector. While compatible with standard RJ45 plugs, etherCON allows a ruggedized and locking interconnection for harsh or high-reliability environments. The Model 381’s operating power is provided by way of the Ethernet interface using the 802.3af Power-over-Ethernet (PoE) standard. This allows fast and efficient interconnection with the associated data network. To support PoE power management, the Model 381’s PoE interface enumerates (reports) to the power sourcing equipment (PSE) that it’s a class 2 (low power) device.

Dante Audio-over-Ethernet
Audio data is sent to and received from the Model 381 using the Dante audio-over-Ethernet media networking technology. The Model 381’s two Dante output (transmitter) and two Dante input (receiver) audio channels can be assigned to other devices (routed) 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 44.1, 48, 88.2, or 96 kHz. Two bi-color LEDs provide an indication of the Dante connection status.

The Model 381 is compatible with the AES67 interoperability standard. In this mode the two transmitter (output) channels will function in multicast; unicast is not supported. In addition, the unit is compatible with the Dante Domain Manager (DDM) software application.

Audio Quality
The Model 381’s performance is completely “pro,” making it appropriate for use in a wide-range of applications. A low-noise, wide dynamic-range microphone preamplifier and associated voltage-controlled-amplifier (VCA) dynamics controller (“compressor”) circuit ensures that mic input audio quality is preserved while minimizing the chance of signal overload. A configuration choice allows selection of the signal source for the Dante main output channel. The choices are either the output of the microphone preamp or the output of the compressor circuit. These choices are referred to as “pre-compressor” or “post-compressor.” The ADC section utilizes a high-performance integrated circuit that supports sampling rates of 44.1, 48, 88.2, and 96 kHz with a bit depth of up to 24. The audio signal, now in the digital domain, routes through a 32-bit microprocessor and on to the Dante interface section where it is packetized and prepared for transport over Ethernet.

Audio input signals arrive via the Dante receiver channels and pass into the Model 381’s microprocessor. As with the Dante audio output channels, the sampling rate can be 44.1, 48, 88.2, or 96 kHz with a bit depth of up to 24. Channel routing, headphone level control, and sidetone creation are performed in the digital domain. This provides flexibility, allows precise control, and keeps the two controls from having to directly handle analog audio signals. The audio channels destined for the headphone output channels 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.

Configuration Flexibility
The Model 381 can be configured to meet the needs of specific applications and user preferences. All configuration tasks are performed using the STcontroller personal computer software application which is compatible with version 7 and later of the Windows® operating systems. There are no mechanical switch settings or button-press sequences required to configure how the unit functions. Selectable parameters include microphone preamplifier gain, P48 phantom power on/off, headphone output performance, sidetone operation, button action, and main output audio source.

The gain of the microphone preamplifier can be selected from among five choices. This allows the Model 381 to match the output sensitivity of a range of handheld and headset-associated microphones. A low-noise source of P48 phantom power can be enabled if required to support condenser (capacitor) microphones. The two Dante input audio sources and the way in which they are assigned to the headphone output channels can be configured. In addition, the operation of the two rotary controls can be selected. These unique choices allow almost any required headphone monitoring situation to be implemented. Whether for use in on-air sports, in an eSports broadcast, or as a production support tool, the Model 381 should be able to achieve the desired configuration.

The integrated sidetone function can be configured to operate from among three choices. This allows audio associated with the microphone input and microphone preamplifier to be returned to the headphone output as required. Sidetone can be important as some applications may provide a “mix-minus” talent cue signal that doesn’t include the user’s own voice content. A configuration selection allows the talkback button to be selected for a push to mute or latching operation. The Dante main output channel can be selected to its audio source to be “pre-” or “post-” the dynamics control circuitry.

Future Capabilities and Firmware Updating
The Model 381 was designed so that its capabilities and performance can be enhanced in the future. A USB connector, located on the unit’s main circuit board (underneath the unit’s cover), allows the application firmware (embedded software) to be updated using a USB flash drive.

The Model 381 uses Audinate’s Ultimo™ integrated circuit to implement the Dante interface. The firmware in this integrated circuit can be updated via the Ethernet connection, helping to ensure that its capabilities remain up to date.