Whether it's the mic preamplifier, audio switching, talkback signals, intercom interfacing, or headphone cue feed, superior audio quality is maintained throughout. A microprocessor provides the Model 230's logic power, allowing precise control of the unit's operation. With extensive flexibility built in, creating the desired operating configuration is a simple matter. While the operating features of the unit can be carefully tailored, the user is presented with an easy-to-use set of controls and indicators. A wide range of resources, great performance, and simplicity during use—these are the hallmarks of the Model 230.
A truly next-generation product, exhaustive research into the needs and desires of field production personnel was integral to the Model 230's creation. Providing a veritable "tool kit" of features, the unit supports a wide variety of applications that include on-air television and radio broadcasting, stadium announcement, and simultaneous interpretation. In addition, with the unit's broad range of capabilities many other specialized "behind-the-scenes" applications can also be implemented.
A high-performance microphone preamplifier circuit provides low-noise/low-distortion amplification over a 20 to 60 dB gain range. The gain is adjustable in 10 dB steps. The input is compatible with balanced dynamic and condenser microphones. The microphone power source is 48 V nominal and meets the worldwide P48 phantom power standard. The preamplifier's gain can also be set for 0 dB, allowing a line-level audio signal to be connected. This could provide useful in special applications such as when an external preamp or mic processor is being used.
An LED indicator serves as an aid for optimizing the preamplifier's gain setting. The output of the microphone preamplifier is used by the main output as well as being routed to the compressor circuit that supports the talkback functions.
The Model 230 provides a main output that is designed to serve as the on-air, stadium announcement, or other primary audio feed. Nominally –2 dBu, it is designed as a fully professional interface with high output capability, low distortion, and low noise. The output circuitry features a high-performance output transformer expressly designed for use in professional audio applications.
The talkback functions are intended to provide personnel associated with production trucks, control rooms, live-performance, and sports venues with talent-originated cue signals. The Model 230 contains two pushbutton switches that control the talkback functions. Each button can be configured to allow talkback audio to be routed to one of three locations: intercom channel 1, intercom channel 2, or a line-level talkback output. The line-level talkback output is transformer-coupled with a +4 dBu nominal signal level. It contains resistors in series with the output connector, allowing line-level talkback outputs from multiple units to be directly "summed."
For non-on-air applications, the Model 230 can be placed in its "production" mode. This software-based mode allows the main output to be used as an additional talkback output. This feature makes the unit even more powerful when used in live-event applications, such as serving as a master console for an orchestra conductor or production director. With this flexibility, the exact needs of many specific applications can easily be met. And, of course, whatever configuration is selected the audio quality will be excellent.
Dynamic Range Control
To enhance the Model 230's talkback functions, a studio-quality compressor circuit is provided to control the dynamic range of the signal coming from the microphone preamplifier. Far from a simple "clipper," the circuit utilizes a sophisticated laser-trimmed voltage-controlled-amplifier (VCA) integrated circuit for quiet, low-distortion level control. The signal from the compressor is used by the talkback functions. This ensures that talkback audio signals remain clear and intelligible under all real-world conditions. In addition, dynamic range control is especially important when talkback signals are being routed to party-line intercom channels.
User Controls and Status Indicators
Three pushbutton switches, four LED indicators, and two rotary controls provide the user with a clear, easy-to-use interface. One pushbutton switch controls the status of the main output. This is the audio output intended for on-air, announcement, or other primary uses. Two LEDs display the on/off status of the main output. Two additional pushbutton switches control the status of the talkback functions. These functions create the audio cue signals used to communicate with producers, directors, "spotters," or other behind-the-scenes production personnel. A status LED is associated with each talkback button. Two rotary controls allow the user to adjust the level of the headphone output.
A large part of the Model 230's unique power is the ability to configure the operation of the main output and talkback functions. To meet the needs of the many specific broadcast and production applications, a variety of button operating modes is available. The main output button can be selected to operate from among four modes. In the "push-to-mute" mode the button performs a momentary mute of the main output. In this way a "cough" button function is created, something typically required for television sports broadcasting. In the "push-to-talk" mode the button provides a momentary active function for the main output. This mode would be appropriate for applications such as stadium announcement. An alternate action "latching" configuration allows the button to enable or disable the main output as desired. This is useful in radio broadcasting, announce-booth, or voice-over applications. The fourth mode provides a hybrid function, supporting both push-to-talk and tap-to-enable/tap-to-disable operation. This operation is similar to that found in many broadcast intercom system user stations.
The two buttons associated with the talkback functions can be configured to operate from among two modes. One of the modes supports a "push-to-talk" function. This is typically used for on-air broadcast applications. The other mode provides a hybrid function, the operation of which is discussed in the previous paragraph. The hybrid mode is especially useful when the Model 230 is used in a production-support application.
The main button mode configures how the main output, when it is in the "latched" on state, responds to talkback activity. One choice momentarily turns off the main output when talkback is active, returning the main output to the on state when the talkback function has ended. The other choice "unlatches" the main output in response to a talkback function.
A broadcast-standard "wet" (DC with audio) IFB circuit can be directly connected to the Model 230's IFB input. Originated by sources such as the RTS™ 4000-series IFB system or IFB interface devices from Studio Technologies, the connected IFB circuit can provide DC power to operate the Model 230 as well as two channels of cue audio.
The Model 230 supports the connection of up to six audio sources, each of which can be selected for routing to the stereo headphone output. The sources are IFB channel 1, IFB channel 2, line input 1, line input 2, intercom channel 1, and intercom channel 2. Each source can be individually assigned to the left channel, right channel, or both left and right. This allows a wide variety of stereo and mono headphone mixes to be created.
The two audio signals associated with the Model 230's IFB input can be assigned to the headphone output. Originating in production trailers or control rooms, the IFB circuits typically provide DC power and program-with-interrupt audio on one channel and program-only audio on the other.
For application flexibility, two line-level audio sources can be connected to the Model 230. Possible signal sources include off-air receivers, wireless IFB systems, and audio consoles. The connected signals can be from two independent sources, or could be from a stereo audio feed such as would be associated with a broadcast music event. Two level trim potentiometers, located on the bottom of the unit, allow signals with wide nominal audio levels to be cleanly interfaced.
Audio signals associated with a single- or dual-channel party-line intercom system can be routed to the headphone output. The Model 230's intercom interface is compatible with standard party-line intercom systems from manufacturers such as RTS and Clear-Com®.
Two rotary controls are provided for user adjustment of the headphone output levels. For application flexibility the actual function of the two "pots" is configurable. For traditional on-air sports applications they can be selected to the dual level control mode which provides independent control of the left and right channel volume. For use with stereo cue signals, or to support user preference, the level/balance mode can be selected. In this mode one control adjusts the overall level of both the left and right channels, while the other allows adjustment of the left/right level balance. To help minimize the chance of broadcast cues being missed, both level control modes can be configured so that a minimum headphone output level is maintained. Alternately, the headphone output can be set to fully mute when the controls are at their minimum position.
A headphone control reverse mode is provided specifically for on-air television applications where a headset with boom microphone is used. The reverse mode ensures that no matter which headset orientation is used by the talent, the controls will always work intuitively. This results in a comfortable work environment, allowing the left control to impact the level to the talent's left ear while the right control impacts the right.
Provision has been made to support applications where a monaural cue feed is desired. A configuration switch allows the summing (combining) of the selected left and right headphone sources. In addition to creating a dual-channel mono output it also allows the level controls to be configured as a simple 2-channel mixer. For applications where a single "muff" headset or IFB earpiece is connected, another configuration switch can be used to disable the headphone output's right channel.
The headphone output is optimized to meet the needs of contemporary headphones and headsets. Specifically, the output circuits act as voltage, rather than power, drivers. In this configuration they can provide high output levels with very low distortion and noise, along with minimal current consumption. The output circuits are configured to safely drive stereo or mono loads. This ensures that all types of headphones, headsets, and earpieces can be directly connected.
Of special note is the Model 230's sophisticated party-line intercom interface. It's designed to work correctly with industry-standard single- and dual-channel party-line intercom systems, including those from RTS and Clear-Com. An intercom line connected to the Model 230 can serve three functions: providing cue audio signals to the headphone output, allowing talkback audio to be sent to intercom users, and as a Model 230 power source. Audio signals present on the single- or dual-channel intercom line can be flexibly routed to the headphone output. Talkback audio can be sent to either or both intercom channels. Trim potentiometers, located on the bottom of the unit, allow adjustment of the talkback-to-intercom null ("sidetone") level.
Other announcer console products can exhibit talkback-to-intercom-related audio oscillations ("squeals") that end up in the headphone output. A special Model 230 feature ensures that this will never occur. This is accomplished by means of a special "auto-terminate" circuit that becomes active whenever an intercom line is not connected to the Model 230.
The Model 230 includes a sidetone function that routes audio from the microphone input to the headphone output as a user confidence signal. This allows a user to always hear what they are saying, a critical requirement for effective communications. The sidetone level can be adjusted using one of the front panel level controls, allowing the user to set it as required for effective use.
Audio Quality and Protection
The Model 230's circuitry is carefully tailored to provide excellent audio performance. Professional-quality components are featured throughout. For reliability all audio routing is performed using solid-state devices under microcontroller direction. In all critical audio paths, "clickless" electronic switches provide noise-free control. All audio inputs and outputs make extensive use of protection components. This limits the chance of damage from ESD and other undesirable, yet real-world, hazards.
The Model 230 can derive its operating power from an IFB circuit, an intercom line, or an external 24 Vdc source. For redundancy, all three power sources can be connected simultaneously. An internal switch-mode power supply ensures that all Model 230 features are available, including phantom power, when the unit is powered by any of the three sources.
The Model 230 is compatible with IFB circuits provided by most standard broadcast systems. However, maximum performance can often be obtained by using IFB interface devices available from Studio Technologies. They provide high-quality audio signals along with an excellent source of DC power. They are directly compatible with most matrix intercom systems, as well as standard line-level audio signals.
Model 230 resources include a general-purpose relay, allowing specialized configurations to be created. Under software control, the relay can be configured to follow the state of the main output, talkback 1, or talkback 2 buttons. Taking advantage of the back-panel locations provided for additional XLR connectors, a technician may easily implement a variety of functions such as an "on-air" indicator or performing loudspeaker muting during talkback. Special configuration modes are even included to allow direct control of the relay using the talkback 1 or talkback 2 buttons without impacting any of the unit's audio signals.
Model 230 configurations are made using a number of DIP switches and four trim potentiometers. One 8-position switch assembly is used to set the gain of the microphone preamplifier, the on/off status of phantom power, and control of the headphone output modes. A 12-position switch assembly configures which of the six cue audio sources are routed to the headphone outputs. Two 8-position switch assemblies communicate the desired operating modes to the microprocessor. Two rotary trim pots are used to adjust the input sensitivity of the line inputs. Two additional rotary trim pots are provided to adjust the "sidetone" level for the intercom interfaces' talkback functions. All switches and trim pots are accessible via the bottom of the Model 230's enclosure; the unit does not have to be disassembled. Changes made to any of the configuration parameters become active immediately. To prevent access to the configuration controls a security plate, included with each unit, is attached to the bottom of the enclosure.
The Model 230 uses standard connectors throughout. The microphone input, line inputs, IFB input, and intercom interface functions use 3-pin female XLR connectors. The main output and line-level talkback output functions use 3-pin male XLRs. The headphone output utilizes a ¼-inch 3-conductor jack. The external source of 24 Vdc power is connected by way of a 2.1 x 5.5 mm "locking" coaxial power jack.
Additional Connector Locations
In the world of broadcast and production audio it's fair to say that applications vary widely. To this end, up to three additional XLR connectors can be easily mounted into the Model 230's back panel. Multiple 3-position "headers" located on the Model 230's circuit board provide technician-access to literally every input and output connection. Using a factory-available interface cable kit, these allow a Model 230 to be optimized to meet the exact needs of specific applications. For example, some applications may prefer to use a multi-pin XLR connector to interface with a headset. This could be easily accomplished by adding the appropriate 5-, 6-, or 7-pin XLR connector and making a few simple connections. Other applications may benefit from having "mult" or "loop-through" connections, something easily incorporated into a Model 230.
Multi-Pin Headset Connectors
As previously mentioned, some broadcast applications use headsets that interface using a multi-pin connector. In most cases these connectors are 5-, 6-, or 7-pin male XLRs wired to an industry-standard pinout scheme. Studio Technologies offers headset connector assemblies that allow fast and painless installation into a spare connector location in the Model 230's back panel.
The Model 230's standard resources are more than sufficient to directly support a large number of applications. But in the "real world" of audio and intercommunications special needs always seem to arise. To that end, Studio Technologies offers a number of option cards. In addition to passive or active components, each card contains an integral connector, allowing simple installation into a spare connector location on the Model 230's back panel. For interest, the resources provided by some of these option cards are worth describing.
- The direct microphone output card provides access to the dynamic or condenser microphone that is connected to the Model 230's mic input. Passive components, along with the auxiliary relay contact, create a "click-free" microphone-level audio signal.
- The line output card allows the Model 230 to provide a second line-level talkback output.
- The remote switch input card uses a 4-pin XLR connector to provide access to the Model 230's remote switch inputs.
- The tally/remote switch input card provides a current-limited DC voltage that serves as a main output status signal. It also provides a remote switch input connection.
Other general purpose option cards provide 3-pin XLR, 4-pin XLR, and 8-pin EtherCon® connectors. With the range of option cards available it's hard to imagine an application that can't be served. But you're welcome to try to "stump the chumps" in the Studio Technologies technical support department! But first please check the complete list of the available option cards.