Headphone Output, Superior Audio Quality Is Maintained Throughout

User Guide

Issue 2, June 2006

This User Guide is applicable for serial numbers: M212-00151 and later

50330-0606, Issue 2 Table of Contents

Introduction ...... 5 System Features ...... 6 Installation and Setup ...... 10 Configuration ...... 15 Operation ...... 24 Technical Notes ...... 27 Specifications ...... 34 Appendix A ...... 35 Block Diagram

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 3 This page intentionally left blank.

Issue 2, June 2006 Model 212 User Guide Page 4 Studio Technologies, Inc. Introduction What This User Guide Covers This User Guide is designed to assist you when installing, configuring, and using the Model 212 Announcer’s Console. Additional background technical information is also provided. A product block diagram is included at the end of this guide. System Overview The Model 212 Announcer’s Console is designed to serve as the audio control center for announcers, commentators, and production talent. With its digital audio Figure 1. Model 212 front panel input and output resources the tabletop unit is well suited for numerous applications including on-air television sports broadcasting. The broadcast-standard interfaces allow direct integration into contemporary “all digital” environments. The Model 212 integrates all on-air, talkback, and cue audio signal routing into one compact system. Some of the unit’s highlights include ease of use, configuration flexibility, and sonic excellence.

Whether it’s microphone preamplification, Figure 2. Model 212 back panel switching of main and talkback audio signals, or the headphone output, superior audio quality is maintained throughout. A A truly next-generation product, extensive microprocessor provides the Model 212’s research into the needs and desires of logic power, allowing precise control of the field production personnel was integral to unit’s operation. A range of choices allows the Model 212’s creation. While primarily the desired operating configuration to be targeted for on-air television applications, easily selected. While flexible, the user is specialized features are included to allow presented with an easy-to-use set of con- the Model 212 to be used in a variety of trols and indicators. The digital audio inter- other audio applications. These include faces are directly compatible with system on-air radio broadcasting, stadium an- environments that use AES digital audio nouncement, and voice-over/narration signals as their preferred transmission booths. method. Unbalanced, 75 ohm interfaces are standard with balanced 110 ohm support also available.

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 5 dynamic range control of the signal can System Features offer increased performance for many applications. This would be appropriate Microphone Input for applications such as stadium an- A high-performance microphone pre- nouncement positions, sports events amplifier circuit provides low-noise/low- using nonprofessional on-air talent, as distortion amplification over a 10 to well as situations where the risk of digital 50 dB gain range. The gain is adjustable “clipping” is present. in 10 dB steps. The input is compatible with balanced dynamic or condenser Main and Talkback Audio microphones. The microphone power source is 48 volts nominal and meets the Channels worldwide P48 phantom standard. An Internally, the Model 212 creates analog LED indicator serves as an aid for optimiz- main and talkback audio channels. The ing the setting of the preamplifier’s gain. main audio channel is designed to serve The output of the microphone preamplifier as the on-air, stadium announcement, is routed to the compressor circuit that or other primary audio feed. The talkback supports the main and talkback audio audio channel is intended to provide channels. production trucks, control rooms, or support personnel with a talent-originated Dynamic Range Control cue signal. The two analog channels are converted to 24-bit PCM digital audio and A studio-quality compressor circuit is multiplexed and formatted into an AES provided to control the dynamic range digital audio “stream.” The A/D converters of the analog signal coming from the and digital transmitter circuitry is synchro- microphone preamplifier. Far from a nized (“locked”) to the selected digital simple “clipper,” the circuit utilizes a input signal. The system will automatically sophisticated laser-trimmed voltage- revert to the internal clock, which provides controlled-amplifier (VCA) integrated cir- a 48 kHz sampling rate. The main audio cuit for quiet, low-distortion level control. channel is assigned to digital channel 1 The output of the compressor is used by with talkback audio on digital channel 2. the main and talkback channels, being The composite digital audio signal routed to the inputs of their respective is routed to two physical interfaces. One analog-to-digital converter circuits. The output is AES3id compliant (unbalanced, threshold of the compressor can be con- 75 ohms) with a BNC connector for inter- figured from among two values. When facing. This professional interface is trans- configured for –4 dBFS dynamic range former-coupled and capable of driving control will only take place as the signal long broadcast cable runs. approaches the level limit of the digital signal. During normal operation the com- The digital audio output signal is also pressor would not be active. With the routed to a unique bidirectional digital compressor configured to –14 dBFS some interface. Similar to AES3id, it uses a dynamic range control would be expected BNC connector and supports two chan- during normal operation. While not appro- nels of audio in each direction over a priate for major on-air situations, having single 75 ohm cable. The bidirectional

Issue 2, June 2006 Model 212 User Guide Page 6 Studio Technologies, Inc. audio interface will find use in specialized the user with a clear, easy-to-use interface. applications, including direct integration One pushbutton switch controls the status with Riedel® intercom systems. Note that of the main audio channel. This is the au- audio signals received from the bidirec- dio signal intended for on-air, announce- tional interface are described in the Cue ment, or other primary uses. Two LEDs Sources section of this document. display the on/off status of the main audio channel. A second pushbutton switch For enhanced flexibility, the Model 212 controls the status of the talkback audio includes the resources to support a third channel. This is the audio signal used to digital output. Circuitry, located on the communicate with producers, directors, printed circuit board assembly, creates spotters, or other behind-the-scenes pro- an AES3 compliant, 110 ohm nominal, duction personnel. A status LED is associ- transformer-balanced digital output. Gain- ated with the talkback button. Two rotary ing access to this output simply requires controls allow the user to adjust the level adding a 3-pin male XLR-type connector of the stereo headphone output. to one of the two spare connector locations on the Model 212’s back panel. Operational Flexibility Connector kits, available from Studio Technologies, make this a simple task. Much of the Model 212’s unique capabili- ties derive from the ability to configure the For specialized applications an optional on/off control of the main and talkback direct microphone output card is available. audio channels. To meet the needs of the This allows the Model 212 to support an many specific broadcast and production analog signal chain for the main output applications, a variety of button operat- channel. Of course this output also pro- ing modes are available. The main but- vides “click-free” microphone on/off ton, located on the left side of the front (“muting”) control. panel, can be selected to operate from The Model 212 isn’t limited for use in “on- among four modes. In the “push-to-mute” air” applications. A special feature can be mode the button performs a momentary enabled, placing the unit in a “production” mute of the main audio channel. In this mode. When this mode is active enabling way a “cough” button function is created, the talkback audio channel will no longer something typically required for television force the main audio channel to mute. This sports broadcasting. In the “push-to-talk” allows the main audio channel to be used mode the button provides a momentary as a second talkback output. In this con- active function for the main audio channel. figuration the unit can be even more pow- This mode would be appropriate for appli- erful when used in a live event application, cations such as stadium announcement. such as serving as a master console for a An alternate action “latching” configura- production director. tion allows the button to enable or disable the main audio channel as desired. This User Controls and Status is useful in radio broadcasting, announce- booth, or voice-over applications. The Indicators fourth mode provides a hybrid function, Two pushbutton switches, three LED supporting both push-to-talk and tap- indicators, and two rotary controls provide to-enable/tap-to-disable operation. This

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 7 operation is similar to that found in many Digital-to-analog conversion circuitry cre- broadcast intercom system user stations. ates two analog “cue” audio signals from the selected digital interface. In on-air The button associated with the talkback broadcast applications these cue signals, function can be configured to operate originating in production trailers, control from either of two modes. One of the rooms, or remote locations, supply pro- modes supports a “push-to-talk” function. gram-with-interrupt audio on one chan- This is typically used for on-air broadcast nel and program-only audio on the other. applications. The other mode provides a Each source can be individually assigned hybrid function, the operation of which is to the left channel, right channel, or both discussed in the previous paragraph. The left and right. This allows a wide variety of hybrid mode is especially useful when the stereo and mono headphone mixes to be Model 212 is used in a production-support created. application. Some applications may benefit by being Cue Sources able to connect standard line-level audio The Model 212 allows two audio channels signals to the Model 212. To meet this from one of three digital audio sources need one or two optional line input cards to be routed to the stereo headphone out- can be installed in the Model 212’s back put. Configuration switches select which panel. Each card provides a female XLR- digital input is active. The available sourc- type connector and transformer-isolated es are the AES3id input, the previously +4 dBu nominal input circuit. Each source discussed bidirectional digital interface, can be individually assigned to the left and the optionally implemented AES3 channel, right channel, or both left and input. The AES3id input is an unbalanced, right. 75 ohm interface that uses a BNC connector. Transformer-coupled, it is compatible Headphone Output with standard unbalanced digital audio Two rotary controls are provided for signals. The bidirectional digital interface user adjustment of the headphone output is similar to AES3id but carries two audio levels. For application flexibility the actual channels in each direction. It is intended function of the two “pots” is configurable. for use in special applications. The AES3 For traditional on-air sports applications input is balanced, 110 ohms, and to use they can be selected to the dual-channel requires the addition of a connector on (“level/level”) mode which provides the unit’s back panel. No matter which of independent control of the left- and the digital inputs is selected, the receiver right-channel volume. For use with dual- circuitry can accept bit depths of 16 to 24. channel cue signals, or to support user While the nominal sample rate is 48 kHz, preference, the stereo (“level/balance”) any signal in the range of 32 to 96 kHz is mode can be selected. In this mode one acceptable. Note that the received clock control adjusts the overall level of both signal is used for two purposes; it allows the left and right channels, while the other correct receiver synchronization as well as allows adjustment of the left/right level serving as the transmitter clock source for balance. To help minimize the chance of the digital outputs. broadcast cues being missed, both level

Issue 2, June 2006 Model 212 User Guide Page 8 Studio Technologies, Inc. control modes can be configured so that a use of protection components. This lim- minimum headphone output level is main- its the chance of damage from ESD and tained. Alternately, the headphone output other undesirable, yet real-world, hazards. can be set to fully mute when the controls are at their minimum position. The rotary Power Sources controls can also be set for a reverse The Model 212 requires an external source left/right mode. This is provided for cases of nominal 24 volt DC, 150 milliamperes where a user needs to wear their headset maximum, for operation. An external pow- “reversed” to support alternate camera er supply is included with each unit. Inside angles. By using this special mode intui- the Model 212, an internal switch-mode tive operation will be maintained and a power supply creates the various voltage comfortable work environment assured. “rails” required by the internal circuitry. Provision has been made to support ap- As an alternative, the Model 44 Interface plications where a monaural cue feed is can be used to power the Model 212. desired. A configuration switch allows the Available from Studio Technologies, it summing (combining) of the selected left serves as an interconnection “hub,” pro- and right headphone sources. In addition viding power and signal routing for up to creating a dual-channel mono output it to six Model 212 Announcer’s Consoles. also allows the level controls to be config- Refer to the Technical Notes section for ured as a simple 2-channel mixer. details. The headphone output was designed to meet the needs of contemporary head- Auxiliary Relay phones and headsets. Specifically, the Model 212 resources include a general- output circuits act as voltage, rather than purpose relay, allowing specialized con- power, drivers. In this configuration they figurations to be created. Under software can provide high output levels with very control, the relay can be configured to low distortion and noise, along with mini- follow the state of the main and talkback mal current consumption. The output cir- audio channels. Taking advantage of the cuits are configured to safely drive stereo back-panel locations provided for addi- or mono loads. This ensures that all types tional XLR-type connectors, a technician of headphones, headsets, and earpieces may easily implement a variety of func- can be directly connected. tions such as providing an “on-air” indicator or performing loudspeaker muting Audio Quality and Protection during talkback. The auxiliary relay is also The Model 212’s circuitry was carefully used by the optional direct microphone tailored to provide excellent audio perfor- output card. mance. Professional-quality components are featured throughout. For reliability all Configuration audio routing is performed using solid- Model 212 configurations are made state devices. In all critical audio paths, using a number of DIP-type switches. One “clickless” performance is provided. All 8-position switch array is used to set the audio inputs and outputs make extensive gain of the microphone preamplifier, the

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 9 on/off status of phantom power, the com- by adding the appropriate 5-, 6-, or 7-pin pressor threshold, and the headphone XLR-type connector and making a few stereo/mono mode. Another 8-position simple connections. Other applications switch array configures which of the may benefit from having “mult” or “loop- audio sources is routed to the headphone through” connections, something easily output. A 12-position switch array commu- incorporated into a Model 212. One or two nicates the desired operating modes optional line input cards, as previously dis- to the microprocessor. All switches are cussed, can also be mounted in the spare accessible via the bottom of the Model XLR positions. 212’s enclosure; the unit does not have to be disassembled. Changes made to any of the configuration parameters Installation and become active immediately. To prevent access to the configuration switches a Setup security panel, included with each unit, In this section interconnections will be is attached to the bottom of the enclosure. made using the input and output connectors located on the Model 212’s back Connectors panel. A microphone signal is interfaced The Model 212 uses standard connectors by way of a 3-pin XLR-type connector. A throughout. The microphone input uses ¼-inch 3-conductor phone jack is provid- a 3-pin female XLR-type connector. The ed for the headphone output. Digital audio digital audio inputs and outputs use BNC input and output connections are made connectors. A ¼-inch 3-conductor jack is using BNC jacks. A 2.1 x 5.0 mm coaxial used for the headphone output. The ex- jack allows connection of the external ternal source of 24 volt DC power is con- 24 volt DC power source. Depending on nected by way of a 2.1 x 5.0 mm “locking” installed options, other connectors may be coaxial power jack. used to connect analog, digital and power signals. In the world of broadcast and production audio it’s fair to say that applications System Components vary widely. To this end, one or two additional XLR-type connectors can easily be The following are included in the shipping mounted into the Model 212’s back panel. carton: Model 212 Announcer’s Console, Multiple 3-position “headers” located on user guide, button label sheet, and 24 volt the Model 212’s circuit board provide DC power supply. For units shipped to technician-access to all input and output destinations in Japan and North America connections. Using a factory-available the power supply will have a nominal interface cable kit allows a Model 212 to AC mains input of 120 volts. For all other be optimized to meet the exact needs of destinations a power supply compatible specific applications. For example, some with 100 to 240 volts AC mains will be applications may prefer to use a multi-pin included. XLR-type connector to interface with a headset. This can easily be accomplished

Issue 2, June 2006 Model 212 User Guide Page 10 Studio Technologies, Inc. Microphone Input suffix “-XQ” to the headset’s part number (HMD25-XQ) specifies a 3-pin male XLR- The Model 212 is compatible with bal- type connector for the dynamic micro- anced dynamic and condenser microphone and a ¼-inch 3-conductor plug for phones. Depending on the application, the stereo headphones. This configura- the microphone may be part of a headset, tion is very useful, allowing the headset or be an independent handheld or stand- to work directly “out of the box” with the mounted model. The Model 212’s 48 volt Model 212. nominal power source will support essen- tially all phantom-powered microphones. If the writer may digress for a moment to The quality of the Model 212’s microphone recount a story… an audio dealer once preamplifier and associated circuitry is shared a secret with me concerning head- such that special applications may benefit sets. He loved selling the “lower-end” (less from using “high-end” microphones. If expensive) models of name-brand head- selected appropriately, models from sets, which he did by the veritable “boat- manufacturers such as AKG, Beyer, DPA, load.” Why? Because these usually broke Neumann, Sennheiser, and Shure will per- soon after going into service! He knew form very well in Model 212 applications. that on a regular basis he’d receive orders for more of them. Had these users, from Microphone interconnection is made by the beginning, purchased only premium- way of a 3-pin female XLR-type connec- quality headsets, their total cost of owner- tor which is located on the Model 212’s ship would have been much less. Enough back panel. The mating connector (male) said… should be wired so that pin 2 is signal high (+ or hot), pin 3 is signal low (– or Headphone Output cold), and pin 1 is shield. It’s possible that an unbalanced microphone will also work The Model 212’s headphone output is correctly. In this case, the mating connec- compatible with stereo or mono head- tor (male) should be wired so that pin 2 phones, headsets, or earpieces. Connect- is signal high (+ or hot), and signal ing devices with a nominal impedance common/shield is connected to both of 100 ohms or greater is preferred. This pins 1 and 3. shouldn’t prove to be an issue as essen- tially all contemporary devices already The Model 212 is not compatible with meet this condition. unbalanced “electret”-type microphones that require a source of low-voltage DC Devices are connected to the headphone for operation. These microphones, some- output by way of a ¼-inch 3-conductor times found in low-cost headsets, are not phone jack located on the Model 212’s generally suitable for on-air or other back panel. As is standard for stereo demanding applications. headphones, the left channel is connected to the “tip” lead of the ¼-inch headphone As of the writing date of this user guide, jack. The right channel is connected to the the Sennheiser HMD25 headset is very “ring” lead of the jack. Common for both popular for on-air sports broadcasting channels is connected to the “sleeve” use. A fine product, it works very well lead. with the Model 212. Note that adding the

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 11 Devices with ¼-inch 2-conductor “mono” as the input source. In this case a valid plugs can also be used with the Model signal must be connected to the bidirec- 212’s headphone output. In this arrange- tional digital interface for proper digital ment only the tip lead (left channel) will audio output signals to be created; the be active. The 2-conductor plug will physi- Model 212 is not be able use its internal cally connect (“short”) the ring lead (right clock source. channel) to the sleeve lead (common). The main output channel is intended to Technically this won’t damage the cir- be the “on-air” signal that connects to cuitry associated with the right-channel an input channel of an audio console. headphone output. (51 ohm protection The talkback output channel is intended resistors are electrically in series with the for connection to control rooms, produc- headphone output circuits.) However en- tion trailers, or other locations where ergy will be wasted if an audio signal com- talent-originated voice cues are required. ing out of the right channel goes into a The nominal level of the digital audio “dead short.” There is a simple solution to signals is –20 dBFS. The actual levels this issue. No cue audio source should be will depend on the gain setting of the assigned to the right-channel headphone microphone preamplifier, sensitivity of the output. Refer to the Configuration section microphone, how loudly the talent speaks of this user guide for details. into the microphone, and the configuration AES3id Output setting of the compressor threshold. The main and talkback audio channels are Talkback audio is also “on-air” quality, accessible by way of an AES3id digital au- which makes sense as the audio path dio output. A BNC connector, located on is shared by the talkback and main out- the back panel of the Model 212, provides put channels. Devices connected to the access to the transformer-coupled inter- talkback output channel can range from face. This type of digital audio interface amplifiers associated with loudspeakers to is commonly used for broadcast applica- inputs on digital matrix intercom systems. tions, providing a 75 ohm unbalanced im- Connecting the talkback output channel plementation of the AES 2-channel digital to devices that allow easy control of the audio standard. The Model 212’s interface signal level can be helpful. For example, provides 24 bit audio signals with a default connecting to a spare input channel on sample rate of 48 kHz. The main output a digital audio console will provide the audio signal will be present on channel 1 resources to add gain or attenuation as of the digital audio signal; talkback audio required. A talkback-associated output will be present on channel 2. path on the audio console can then connect to the final destination(s). Note that the clock source for the digital audio output is derived from the selected Optional AES3 Output digital audio input. Should the input Circuitry contained within the Model 212 source not be present the Model 212’s allows a technician to add support for an internal clock source will automatically AES3 output. This type of interface allows be selected. The exception is when the two channels of digital audio to be car- bidirectional digital interface is selected ried over a balanced 110 ohm circuit. In

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 12 some Model 212 applications the AES3 Optional AES3 Input output will be implemented using a 3-pin Circuitry contained within the Model 212 male XLR-type connector installed in the allows a technician to add support for a back panel. Other applications may use a standard AES3 input. This type of interface multi-pin connector, such as the Neutrik® allows two channels of digital audio to be EtherCon® version of the 8-pin RJ45 jack. received over a balanced, transformer- Note that the signal coming out of the coupled, 110 ohm circuit. In some Model AES3 output will be identical to that com- 212 applications the AES3 input will be ing out the Model 212’s AES3id output. implemented using a 3-pin female XLR- The same content will be transmitted at type connector installed in the back panel. the same bit depth and clock rate. For Other applications may use a multi-pin full isolation separate circuitry, including connector, such as the Neutrik EtherCon matching transformers, is provided for the version of the 8-pin RJ45 jack. two outputs. As with the AES3id input, for the AES3 AES3id Input input to be active the appropriate configuration DIP switches must be set. And The AES3id input can be used to connect as with the AES3id input, in additional digital audio signals to the Model 212. to providing cue audio sources for the The two audio channels associated with stereo headphone output, the AES3 the interface will serve as cue sources for input will also serve as the clock source the stereo headphone output. The input, for the Model 212’s digital outputs. physically a BNC connector located on the Model 212’s back panel, allows a Bidirectional Digital Interface depth of up to 24 bits to be supported; The Model 212 includes a bidirectional however anything in the range of 16 to digital interface for use in special applica- 24 bits will work correctly. The input is tions. Using a single 75 ohm, unbalanced “self-clocking” so that compatibility with connection, two channels of digital audio virtually any AES3id source should be can be both sent and received. The two possible. It’s expected that in most cases channels of receive audio can be used the Model 212 will be used in professional as cue sources for the stereo headphone audio environments where the sample rate output. Bit depths of up to 24 and sample will be 48 kHz. However, any source with rates of 32 to 96 kHz are supported. For a sample rate from 32 to 96 kHz will also the bidirectional digital interface to be work correctly. active the appropriate configuration DIP For the AES3id input to be active a con- switches much be set. figuration setting must be correctly made. The ability of the bidirectional digital in- This topic is discussed in detail in the terface to send and receive digital audio configuration section of this user guide. signals over one cable makes intercon- It’s also important to note that the selected necting the Model 212 with other equip- digital input source will also serve as the ment incredibly simple. For example, the clock source for the Model 212’s digital bidirectional digital interface is directly outputs. compatible with the Riedel Artist® digital

Issue 2, June 2006 Model 212 User Guide Page 13 Studio Technologies, Inc. matrix intercom system. A single cable customized labels to the button caps is all that is required to interface an Artist would be very simple. The labels, text digital port with the Model 212. printed on clear material, are placed under the clear caps on the top of the buttons. Optional Analog Line Inputs From the factory the left button is While the Model 212’s headphone sources labeled COUGH and the right button is were designed primarily to be supplied labeled TALKBACK. This was selected using one of the digital audio inputs, it’s to be appropriate for many on-air applica- also possible to connect one or two ana- tions in English-speaking locations. But log line-level audio sources. Please refer it’s expected that these may need to be to the Technical Notes section of this user changed to meet the needs of specific guide for details. applications. External Power Input As a “head start” for some applications, a clear sheet with a number of commonly The Model 212 requires an external used button designations printed on it is source of 24 volt DC power for operation. included in the shipping carton. These It is connected by way of a 2.1 x 5.0 mm were created at the factory using a stan- coaxial power jack which is located on dard personal computer graphics program the back panel of the unit. The center pin and laser printed onto 3M CG3300 trans- of the jack is the positive (+) connection. parency film. The desired button labels While the requirement for the external can be cut out with a pair of scissors, fol- source is nominally 24 volts, correct lowing the printed guide lines that indicate operation will take place with any source the required size. within the range of 20 to 30 volts. A maximum current of 150 milliamperes at 24 The clear lens on top of each button cap volts DC is required. Included with each can be removed with a fingernail or small Model 212 is a 24 volt DC external power screwdriver. Be certain not to scratch the supply. The power supply’s DC output button if a screwdriver or other small tool cable has been terminated with a Switch- is used. The clear label can be removed craft® S760K coaxial power plug. This and replaced. The button cap is then “locking” type of plug correctly mates snapped back into the top of the button with the Model 212’s 24 Vdc input jack. housing using finger-pressure only. No The locking feature is important, allowing tool is required to replace the button cap. the external power source to be securely If you need to make your own labels the attached to the Model 212. process is quite simple. Use a personal computer to create the desired text. The Pushbutton Labeling finished label size should be 0.625-inches The two pushbutton switches used in (15.8 mm) square. The completed artwork the Model 212 were selected for several can then be printed on transparency film reasons. Foremost was the fact that they sheets using a laser or inkjet printer. These are highly reliable, using gold-plated con- sheets are readily available from most tacts for long life in less-than-ideal environ- office supply stores. A pair of scissors or ments. A second reason was that applying an X-ACTO® knife will complete the task.

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 14 accessed through openings in the bottom Configuration of the Model 212’s enclosure. The enclo- For the Model 212 to support the needs sure does not have to be disassembled to of specific applications a number of op- gain access to the switches. erating parameters must be configured. To prevent unauthorized personnel from These include microphone preamplifier changing the configuration settings, a se- gain, phantom power on/off, headphone curity plate is attached to the bottom of the cue source selection, headphone mono/ Model 212’s enclosure. For convenience, stereo mode, and a number of operating a configuration settings label is attached modes. Two 8-position and one 12-posi- to the security plate. It provides a summary tion DIP-type switch assemblies are used of the configurable parameters and related to establish the desired configuration. information. Refer to Appendix A for a These switch assemblies are referred to representative view of the label. The secu- as Switch 1, Switch 2, and Switch 3, with rity plate is held in place by means of four individual switches designated as SW1-1, rubber bumpers (“feet”) that have built-in SW1-2, etc. The switch assemblies are screws. Using your fingers, remove the four bumpers so that the plate can be removed. Refer to Figure 3 for a detailed view of the configuration switch assemblies. Microphone Preamplifier Gain and Phantom Power Five switches are used to set the gain of the microphone preamplifier. One switch is used to select the on/off status of the phantom power supply. Microphone Preamplifier Gain Switches SW1-1 through SW1-5 are used to select the gain of the microphone preamplifier. The choices are 10, 20, 30, 40, and 50 dB. Only one switch should be enabled at a time. There’s no problem changing the gain setting while the unit is operating. Audio clicks or pops might occur during gain transitions, but this shouldn’t be a major issue as long as associated monitor loudspeakers are temporarily attenuated or muted. Selecting the correct amount of gain for Figure 3. Bottom view of Model 212 showing an application might take a little experimen- configuration switches and compressor active tation. The goal is to bring the mic’s signal LED

Issue 2, June 2006 Model 212 User Guide Page 15 Studio Technologies, Inc. is located adjacent to switch assembly 1. It is visible by observing the bottom of the Model 212’s enclosure when the security plate has been removed. Technically, this red LED lights whenever the compressor circuitry is controlling the dynamic range of the signal coming from the microphone preamplifier. Using configuration DIP switch SW1-7, the compressor’s threshold will be set to either –14 or –4 dBFS. (Details concerning setting the compress threshold are discussed later in this user guide.) If the threshold is set for –14 dBFS a good “rule of thumb” is to adjust the gain of the microphone preamplifier such Figure 4. Microphone preamplifier gain switch that the compressor active LED will light settings (“flash”) only when the connected micro- level up such that the main and talkback phone is sending signal peaks. During output levels will match the Model 212’s normal operation the LED should never nominal digital output level which is –20 remain fully lit when audio of typical signal dBFS. Operating at this signal level will level is present on the mic input. help to ensure the delivery of “clean” If the threshold is set for –4 dBFS the audio with adequate level “headroom.” LED should light only on extreme signal The output of the Model 212’s microphone peaks, or possibly never. This is because preamplifier is routed to the input of the with a –4 dBFS threshold the compressor compressor circuit. is intended only to prevent signals from Unfortunately, there’s no “perfect” gain ever causing the maximum digital level of setting that this guide can recommend. 0 dBFS to be reached. It’s not supposed The two issues that impact the setting to reduce the dynamic range of normal are output sensitivity of the connected program material. As an aid in setting the microphone and the acoustical output microphone preamplifier’s gain, it might level of the microphone’s user. With useful to temporary set the compressor’s some headset microphones, such as the threshold to –14 dBFS. Once the gain has Sennheiser HMD25, selecting an initial been set so that the LED lights only on setting of 30 dB is appropriate. Users peaks the threshold can be returned to the who speak loudly might need to have –4 dBFS setting. the gain reduced to 20 dB. Quiet users It’s expected that the 10 and 50 dB gain might need 40 dB of gain. settings will not be used often. But there An LED indicator is provided as an aid are always exceptions and that’s why they in correctly setting the gain of the micro- are included. It’s possible that with a very phone preamplifier. Red in color, this LED “hot” microphone, such as a phantom- powered condenser-type, 10 dB of gain

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 16 could be correct. It’s also possible that a Headphone Source Selection microphone with a very low-level output, Switch assembly SW2 is used to configure such as a ribbon-type, would need 50 dB of the source or sources that are routed to gain. But in general, the 20, 30, and 40 dB the stereo headphone output. Up to four gain settings will serve most applications. sources may be available with the choices Note that if no gain switch is set to its active being digital input channel 1, digital input (on) position the preamplifier will operate channel 2, auxiliary input 1, and auxiliary at unity (0 dB) gain. In this mode the pre- input 2. The digital input channels are pro- amplifier will remain stable, but is intended vided by the selected digital input source. for use only during factory testing. A valid The digital input source is configured exception would be where a line-level sig- from these choices: the AES3id input, the nal is connected to the microphone input. optional AES3 input, or the bidirectional This could occur with a special Model 212 digital interface. The auxiliary inputs are application. But with a microphone con- analog and available only if optional line nected as the input source one should input cards have been installed. Alternate- never use the 0 dB setting. The issue is ly, a special Model 212 configuration may that with no gain added to the microphone have been implemented that uses one or input signal, the relative noise floor on the both of the auxiliary inputs. main and talkback output channels will be much too high. In conclusion, the 0 dB gain setting doesn’t highlight a problem, but simply reflects the unit’s gain structure. Phantom Power The Model 212 can provide 48 volt phantom power to the microphone input. Switch SW1-8 controls whether or not phantom power is active. By phantom power’s very nature it could be left applied to the microphone input at all times. But generally people prefer to turn it off unless it is required for a specific microphone.

Figure 5. Phantom power switch settings Figure 6. Left and right channel headphone source selection settings

Issue 2, June 2006 Model 212 User Guide Page 17 Studio Technologies, Inc. Each of the available input sources can be A specific application where this can assigned to the headphone output’s left occur is when on-air talent needs to have channel, right channel, or both the left and a headset’s boom microphone come right channels. The Model 212’s circuitry across the right side of their face, rather allows any combination of input assign- than the more-typical left side. In this case ments to be made. For example, consider it’s important to select the left- and right- the situation where a single digital input channel headphone source assignment channel is actively connected to the Model accordingly. With the Model 212’s flexible 212. In this case it may be desirable to source selection there’s no reason why assign this signal to both the left and right users, such as on-air talent, shouldn’t headphone channels. This would entail have their cue sources assigned correctly. setting switches SW2-2 and SW2-6 to their There may be cases where a monaural on positions. All other switches would “single-muff” headset or headphone will remain in their off positions. be connected to the Model 212’s head- A more complex application might have a phone output. In this case the desired cue 2-channel digital audio signal connected source(s) should be routed only to the left to the Model 212, with an optional line channel. No sources should be assigned input card installed. Line-level audio from to the right channel. This will eliminate the a golf event “spotter” is connected to the short-circuit current that could occur when line input. In a case such as this, it would a 2-conductor (monaural) plug is mated be typical for digital input channel 1 to with the Model 212’s 3-conductor (stereo) be assigned to the headphone’s left headphone output jack. channel, digital input channel 2 assigned to the right channel, and auxiliary input 1 Headphone Output Mode also assigned to the right channel. This Switch SW1-6 allows a monaural head- would allow both digital input channel phone output to be created. This is 2 and “spotter” audio to be heard in the accomplished by summing (adding) the headphone’s right-channel output. To selected left- and right-channel cue sig- achieve this would require that switches nals. The combined signals are sent to SW2-1, SW2-6, and SW2-7 be placed in both the left- and right-channel headphone their on positions. Note that using another output driver circuits. The outputs of these Studio Technologies 200-series announc- circuits connect, by way of 51 ohm series er’s console at the “spotter” location could protection resistors, to the headphone also prove effective. It would provide all output jack. the necessary microphone preamplifier, talkback routing, and headphone monitor- ing resources. In some cases a user may wish to wear a headset or a pair of headphones in a left/ right orientation opposite of what’s usual. In this situation the transducer designated for the left ear would actually supply audio Figure 7. Headphone output mode settings to the user’s right ear, and vice versa.

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 18 The headphone output monaural mode options and choose the ones that best feature was specifically included so that meet the needs of a specific application. a special “2-channel headphone mix” Note that switches can be changed even mode can be created. By enabling the while the Model 212 is powered up and mono mode, the two front-panel user level operating. The unit’s operating character- controls (“pots”) can be used to create istics will change in “real-time” in response the desired “mix” of signals being sent to configuration changes. to the headphone output. Many applications, especially in production settings, Main Output Button Mode can benefit from this capability. The Switches SW3-1 and SW3-2 configure desired cue sources must be carefully how the main output button functions. assigned to take advantage of the monaural mode. The first cue source should be assigned, using the DIP-type switches, to the left channel. Its output level will be adjusted by the left control. The second cue source should be assigned to the right channel. Its output level will be adjusted by the right control. There is one limitation related to the headphone mono output mode. It’s the fact that the output will be 2-channel mon- Figure 8. Main output button mode settings aural. Whatever signal is present on the headphone output’s left channel will also There are four available modes: be present on the right channel. A stereo headphone mix can’t be created. But in • Push to mute: In this mode the main most cases this limitation won’t over- output channel is normally active. The shadow the benefit of being able to create main output channel will mute (have the mix. For signal-flow clarification please minimum digital audio level) whenever review the block diagram located at the the button is pressed and held. This is end of this user guide. the “cough” mode typically used for on-air sports broadcasting applications. Operating Modes • Push to talk: In this mode the main The twelve switches associated with output channel is normally muted. switch assembly 3 are used to configure The main output channel will become the Model 212’s operating modes. Techni- active whenever the button is pressed cally, these switches “talk” to the micro- and held. controller integrated circuit and associated • Alternate action: In this mode the main software that give the Model 212 its output channel will change between “smarts.” The software has been carefully its active and muted state whenever designed to provide a number of different the button is pressed. Upon power up ways in which the unit can function. It’s the main output channel will be in its critical to carefully review the available muted state.

Issue 2, June 2006 Model 212 User Guide Page 19 Studio Technologies, Inc. • Hybrid: This mode is a combination of Headphone Output Operating Modes push to talk and alternate action. It’s The user is provided with two rotary level similar to the way talk buttons function controls (“pots”) that are associated with on user stations associated with broad- the stereo headphone output. Switches cast and production intercom systems. SW3-4, SW3-5, and SW3-6 are used to If the button is pressed and held, the configure the way the controls function. main output channel will become active With just these three switches a wide until the button is released. If the button range of operating modes can be con- is momentarily “tapped” the main output figured. Carefully reviewing the capabili- channel will change state. Upon power ties of the available functions may prove up the main output channel will be in its worthwhile. muted state. Dual-Channel or Stereo Mode Talkback Output Button Mode Switch SW3-4 is used to select whether Switch SW3-3 configures the way the talk- the controls provide a dual-channel back output button functions. (“level/level”) or stereo (“level/balance”) mode of operation. In the level/level mode the two controls operate independently, each controlling the level of one of the headphone output channels. This mode is generally used for on-air broadcast applications where independent cue signals are provided to the left- and right- Figure 9. Talkback output button mode settings headphone channels. In the level/balance mode the left rotary control sets the overall Two modes are available: output level for both headphone channels. • Push to talk: In this mode the talkback The right rotary control is used to adjust output channel is normally muted (mini- the balance (the relative levels) of the left mum digital audio level). The talkback and right channels. This mode is generally output channel will become active best suited for applications where a stereo whenever the button is pressed and cue source is being provided. held. • Hybrid: This mode is a combination of push to talk and alternate action. If the button is pressed and held, the talkback output channel will become active until the button is released. If the button is momentarily “tapped” the talkback Figure 10. Headphone control mode settings output channel will change state. Upon power up the talkback output channel will be in its muted state.

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 20 Reverse Left/Right Mode in a reverse orientation. This ensures Switch SW3-5 is used to select whether that the user is provided with a consistent the rotary controls are in the normal or and easy-to-use set of headphone level reverse left/right mode of operation. controls. When selected to the normal mode, and Minimum Level Mode level/level mode is also selected, the left control adjusts the level of headphone Switch SW3-6 is used to configure the output’s left channel. (This is the signal headphone output’s minimum level. In the that appears on the tip lead of the –40 dB mode the minimum headphone ¼-inch 3-conductor jack.) The right con- output level is 40 dB below maximum. The trol adjusts the level of the right channel. headphone output channels will never fully When selected to the normal mode, and mute. This ensures that any audio signal the level/balance mode is also selected, present on the selected cue audio source turning the balance control in the coun- will always be present on the headphone terclockwise direction increases the per- output. In most on-air broadcast applica- ceived level of the left channel output, tions this is the appropriate setting. and vice versa. When the full mute mode is selected, As you may have already guessed, when and the level/level mode is also selected, selecting the reverse left/right mode of moving either control to its fully counter- operation everything is reversed! To be clockwise position will cause its associ- more specific, when selected for reverse ated channel to fully mute. mode, and the level/level mode is also When the full mute mode is selected, and selected, the left control adjusts the head- the level/balance mode is also selected, phone output’s right channel (output turning the level control to its fully coun- jack’s ring lead) while the right control terclockwise position will cause both adjusts the left channel. When selected to headphone channels to mute. Turning the the reverse mode, and the level/balance is balance control to either its fully clock- also selected, turning the balance control wise or fully counterclockwise position will in the counterclockwise direction increas- cause the appropriate channel to mute. es the perceived level of the right channel output, and vice versa. Selecting the full mute mode may be appropriate for applications where mini- The reverse mode is provided specifically mizing the chance of audio “leakage” for cases where a headset’s left and right ear pieces are placed on a user’s head

Figure 12. Headphone output minimum level settings Figure 11. Headphone control operation settings

Issue 2, June 2006 Model 212 User Guide Page 21 Studio Technologies, Inc. is important. This could occur when the people refer to this generically as an “AES” connected headset or headphones are at digital audio signal. But this is confusing times placed on a desk or tabletop. and inaccurate as there are separate standards for 75 ohm unbalanced (AES3id) Digital Input Source and 110 ohm balanced (AES) digital audio Switches SW3-7 and SW3-8 are used to signals. (While the standards are separate, select which one of the three digital inter- both share the same method of formatting faces will be used by the Model 212 as its the digital audio and control signals.) audio source and reference clock input. The two audio channels associated with The bidirectional digital interface is a the selected digital input can be assigned special type of 75 ohm unbalanced signal to the headphone output channels. In that carries two channels of digital audio addition, the clock signal derived from the in each direction. To clarify, over a single selected digital input is used by the digi- unbalanced cable two channels of digital tal audio circuitry. This clock signal is the audio are sent in one direction and two master “sync” reference that the Model channels of digital audio are sent in the 212 uses for the analog-to-digital conver- other. The bidirectional digital interface sion and digital audio transmission func- uses a BNC connector which is located on tions. The digital input interface choices the Model 212’s back panel. The interface are AES3id In, bidirectional digital inter- is only appropriate for use in carefully en- face, and AES3 In. As selecting the correct gineered systems that are compatible with interface is critical to proper Model 212 this type of signal. An example application operation it’s worth describing each is where a Model 212 is directly interfaced in detail. with a 75 ohm port on a Riedel digital matrix intercom system. The AES3id input is located on the Model 212’s back panel and is compatible with AES3 input circuitry is located inside the unbalanced 75 ohm digital audio signals. Model 212’s enclosure and is compatible This type of signal is common to broad- with balanced 110 ohm digital audio cast facilities where audio and video utilize signals. This type of signal is typically a common cabling-type and BNC connec- found in non-broadcast applications tors for signal transport. Note that many where the use of twisted pair wiring with a maximum interconnection length of 100 meters does not pose a problem. The Model 212 provides AES3 input circuitry for installer-selected applications where the desired connector is mounted into one of the spare connector locations on the Model 212’s back panel. Many applications use standard 3-pin female XLR-type connectors for AES3 inputs. However, using other connector types, such as Neutrik EtherCon, can be a convenient way of Figure 13. Digital input source settings transporting a number of different signals over “CAT5” or “CAT6” twisted-pair cable.

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 22 Incorrectly setting the digital input source System Modes will probably prove to be the most com- Switch SW3-12 is used to configure the mon cause of incorrect Model 212 opera- overall operating mode of the Model 212. tion. Carefully reviewing the connected Specifically, it determines how the main signals and then selecting the appropriate output channel operates vis-à-vis the talk- interface will lead to successful operation. back output channel. Understanding how Relay Mode the two modes impact overall system operation will ensure that correct operation Switches SW3-9 and SW3-10 are used and maximum usability will occur. When to configure the operating mode of the the on-air mode is selected, the main auxiliary relay. output channel will mute (minimum digital audio signal level or –infinity) whenever the talkback output channel is active. The LED indicators associated with the main output button will light accordingly. The on-air mode should be selected for all on- air broadcast applications. It’s imperative that the main output channel be muted whenever on-air talent uses the talkback output channel to communicate with production personnel.

Figure 14. Relay mode settings When the system mode is set for production, the main output channel is never Three modes are available: muted in response to the talkback output channel being active. In this way the main • Relay is disabled: In this mode the relay and talkback output channels can be used is disabled and will never change state. independently, with neither impacting the • Follows main output status: In this mode other. An example of where this would be the relay will follow the state of the main useful is allowing the Model 212 to provide output channel. Specifically, the relay two independent talkback functions; the will change state (energize) whenever main and talkback buttons can be used the main output channel is active. independently or simultaneously. The production mode can prove very useful when • Follows talkback button status: In this selected for the correct application, but it’s mode the relay will follow the state of the not appropriate for on-air use! talkback output channel. Specifically, the relay will change state (energize) state whenever the talkback output channel is active.

Figure 15. System mode settings

Issue 2, June 2006 Model 212 User Guide Page 23 Studio Technologies, Inc. Conclusion Main Output Button and LED Indicators Once the multitude of DIP switches have The button on the left, factory labeled been set to their desired configuration, as COUGH, functions according to the se- the security plate should be reattached. lected configuration. Two LED indicators, The four rubber bumpers should be hand- located directly above the button, are as- tightened only. No tools should be used. sociated with the status of the main output channel. The green LED, located on the right, is lit whenever the main output chan- Operation nel is active. This could be considered as At this point the desired input, output, an “on-air” or mic active indicator. At the and power connections should have been least it should serve as a “careful what you made. The button labels may have been say” warning! If the Model 212’s system revised. Finally, the configuration switches mode is configured to on-air, the red LED, should have been set. Normal operation of located on the left, will be lit when the the Model 212 can now begin. The unit will main output channel is muted. This indi- begin functioning as soon as the source of cates that it’s safe to speak as one sees fit. nominal 24 volts DC is connected. If the Model 212’s system mode is config- Upon Model 212 power up, the three ured to production, the red LED will never status LEDs will light in succession as a light. This is to reflect the fact that the main firmware “boot up” indication. The unit will output button has now taken on a function then begin normal operation. Depending similar to that of the talkback output but- on the selected configuration, one LED ton. To clarify, when the Model 212 is set associated with the status of the main out- to the production mode, the red LED will put may be lit. The user is now presented never light; the green LED will light when- with two buttons, three LEDs, and two ever the main output channel is active. rotary controls. These are simple to oper- Main Output Button Modes ate and understand, as will be described • Push to mute: If this mode is selected in the following paragraphs. the main output channel is normally Pushbutton Switches and active. The main output channel will mute whenever the button is pressed Status LEDs and held. Two pushbutton switches are used to • Push to talk: If this mode is selected the control the main and talkback output main output channel is normally muted. channels. The way each operates de- The main output channel will become pends on the selected configuration. active whenever the button is pressed Three LED indicators are located adjacent and held. to the buttons. They reflect the status of the main and talkback output functions. • Alternate action: If this mode is selected the main output channel will alternate between its active and muted states whenever the button is pressed. Upon power up the main output channel will be in its muted state.

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 24 • Hybrid: This mode is a combination of Talkback Output Button Modes push to talk and alternate action. It’s • Push to talk: If this mode is selected similar to the way talk buttons function the talkback output channel is normally on user stations associated with broad- muted. The talkback output channel will cast or production intercom systems. If become active whenever the button is the button is pressed and held, the main pressed and held. output channel will become active until the button is released. If the button is • Hybrid: This mode is a combination of momentarily “tapped” the main output push to talk and alternate action. If the channel will change state. Upon Model button is pressed and held, the talk- 212 power up the main output channel back output channel will become active will be in its muted state. until the button is released. If the button is momentarily “tapped” the talkback Main Output vis-à-vis Talkback Activity output channel will change state. Upon This short section applies only to the case Model 212 power up the talkback output where the Model 212’s system mode is channel will be in its muted state. configured for on-air and the main output Headphone Output Level Controls button mode is set to alternate action or hybrid. Two rotary controls (“pots”) are located on the Model 212’s front panel and are Talkback activity will always cause the associated with the headphone output. main output channel to be placed in its The way the controls function depends off state. If the main output channel was on the selected configuration. One in the “latched” on state when talkback configuration parameter sets the controls began, once talkback activity ends that to operate in a level/level or a level/ state will resume; the main output channel balance mode. Another parameter allows will again be in its on (“latched”) state. the left/right assignment of the controls Talkback Output Button and LED to be reversed. A third parameter selects Indicator whether the headphone output channels will maintain a minimum output level or The button on the right, factory labeled can be fully muted. TALKBACK, controls the talkback output channel. The manner in which the talk- Level/Level Mode back button functions depends on the When set to the level/level mode, the two way it was configured. One LED indicator, controls operate independently. Each green in color, is located directly above control sets the output level of one chan- the talkback button. It lights whenever nel of the stereo headphone output. If con- the talkback output channel is active. If figured to the normal mode, the control the Model 212’s system mode is selected on the left side is used to adjust the level to on-air, whenever the talkback function of the headphone output’s left channel. is active the main output channel will be The control on the right is used to adjust placed in its muted state. If the Model 212 the level of the right channel. If configured is selected to the production mode, the to the reverse left/right mode, the control status of the talkback output channel will on the left side adjusts the headphone not impact the main output channel.

Issue 2, June 2006 Model 212 User Guide Page 25 Studio Technologies, Inc. output’s right channel. The control on the control on the left adjusts the overall level right adjusts the left channel. of both the left and right channels. The balance control, located on the right, When in the level/level mode, and the adjusts the relative left/right level bal- minimum output level is set for –40 dB, ance. In this mode the controls operate turning each control to its fully counter- in a manner reminiscent of a consumer clockwise position will place its respective audio amplifier or receiver. If set to the output level 40 dB below its maximum. normal mode, rotating the balance control This setting ensures that talent will never in the counterclockwise direction reduces be fully “isolated” from potentially impor- the level of the right channel providing tant cue signals. If present on the Model the user with more perceived level in the 212’s input and assigned to the head- left channel. If set to the reverse mode, phone channels, some audio signal will rotating the balance control in the coun- always be present on the headphone terclockwise direction reduces the level output. If set to the full mute mode, turning of the left channel providing the user with each control to its fully counterclockwise more perceived level in the right channel. position will cause its respective output to fully mute. When in the level/balance mode and the minimum output level is set to –40 dB, Each level control has a mechanical turning the level control to its fully coun- step (detent) that is located at the halfway terclockwise position will place both head- (50%) position of its rotation range. This is phone output channels to 40 dB below intended to serve as an aid to Model 212 maximum. This ensures that talent will users. In an ideal installation, setting the never be fully “isolated” from potentially controls to their detent position will result important cue signals. In addition, rotat- in a comfortable headphone output level. ing the balance control to either its fully The user, in response to a changing op- clockwise or fully counterclockwise posi- erating environment, can then move the tion will cause the applicable channel to level controls to get more or less level as be 40 dB below its maximum. If set to the desired. The detent position will always full mute mode, turning the level control remain as a useful reference point. To to its fully counterclockwise position will achieve this condition the audio levels cause both the left and right channels to on the selected cue sources would have fully mute. In addition, rotating the balance to be adjusted as required. This is some- control to either its fully clockwise or fully what counter to the usual mentality of just counterclockwise position will cause the providing the user with whatever level applicable channel to fully mute. comes up by default. Spending a few extra minutes “trimming” the audio levels Each control has a mechanical step can result in much happier, and more pro- (detent) that is located at the halfway ductive, talent. (50%) position of its rotation range. The balance control will typically be set to its Level/Balance Mode center, detent position, making the level When set to the level/balance mode, the of the left and right channels equal. In an two controls operate together to adjust ideal installation, the level control can also the desired headphone output level. The be set to its detent position and provide a

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 26 comfortable headphone output level. This connector openings located on the Model will allow the user, in response to their 212’s back panel. It’s recommended that, preference or a changing environment, when viewed from the back, the EtherCon to adjust the level and balance controls kit be mounted on the left side with the as desired. The detent positions will al- metal locking tab facing to the left. ways remain as a useful reference point. Three jumper cable assemblies, provided To achieve this condition the audio level with the EtherCon kit, are used to link the on the connected sources must be ad- Model 212 with the appropriate pairs on justed as required. Spending a few extra the EtherCon connector. The Model 212’s minutes “trimming” the connected audio AES3 output is accessible on 3-pin header signals, rather than just providing what- P8 and should be connected to 3-pin ever happens to come up, should prove header P14 on the EtherCon kit’s printed worthwhile. The result will be talent that is circuit board. The Model 212’s AES3 input more relaxed, and an overall production is accessible on header P9 and should be that works more smoothly. connected to header P15 on the EtherCon kit’s printed circuit board. The Model 212’s Technical Notes power input is accessible using header P10 and should be connected to header Model 44 Interface P13 on the EtherCon kit’s printed circuit Some applications may benefit from us- board. ing the Model 44 Interface which is also Once this has been completed standard available from Studio Technologies. The computer-style patch cables can be used single-rack-space unit provides operat- to link the Model 212 with a port on the ing power and digital audio interconnec- Model 44 Interface. These cables, often tion for up to six Model 212 Announcer’s called “CAT5” patch cables, are “straight Consoles. Each Model 212 interconnects through” and organize their four twisted with an RJ45 port on the Model 44 using a pairs as pins 1 and 2, pins 3 and 6, pins 4 single 4-pair “CAT5” or “CAT6” Ethernet- and 5, and pins 7 and 8. For reference the style cable. One pair of the twisted-pair EtherCon Connector Card Kit implements cable supplies 24 volts DC to the Model this interconnection scheme: pins 1 and 2 212. Two additional pairs transport digital carry digital audio to the Model 44, pins 3 audio to and from the Model 212’s AES3 and 6 bring digital audio from the Model interface. A fourth pair is available for 44 to the Model 212, and pins 7 and 8 installer-specified functions. Details about bring 24 volt DC power from the Model 44 the Model 44 are available on the Studio to the Model 212. The power is polarity Technologies website. sensitive with positive on pin 7 and nega- The EtherCon® Connector Card Kit tive on pin 8. (Studio Technologies, Inc. part number 31207) offers a simple means of preparing Phantom Power a Model 212 for use with a Model 44 The Model 212 provides a 48 volt nominal Interface and Ethernet-style interface source of “phantom power” to support cables. This optional card kit is intended condenser-type microphones. It’s de- to be mounted in one of the two spare signed to meet the P48 requirements

Issue 2, June 2006 Model 212 User Guide Page 27 Studio Technologies, Inc. as specified in the IEC 61938 standard. blue—these days there are lots of choices The required circuitry is very simple: two available. The only limitation is the amount 6.81 k ohm resistors provide a path from a of current available to light each LED. 48 volt source to pins 2 and 3 of the micro- Using series resistors of no less than phone input connector. The resistors and 560 ohms will ensure correct Model 212 the power source work together to provide operation. 48 ±4 volts, up to a maximum current of A qualified technician can easily revise the 10 milliamperes. LED colors to meet an application’s exact LED Colors needs. The process would begin by disas- sembling the Model 212’s enclosure and As previously described, two LED indica- detaching the pushbutton/LED printed tors are associated with the main output circuit board assembly. The LEDs would and are located directly above the main then be unsoldered, removed, and rein- output pushbutton switch. The red LED, stalled (or replaced) in the desired loca- located on the left, is lit whenever the tions. To control the LED current and set main output channel is muted. The green the brightness, a resistor is electrically in LED, located on the right, is lit whenever series with each LED. From the factory, the main output channel is active. The an 820 ohm, ¼-watt resistor is associated thought behind the color choices was with the red LED while a 560 ohm, ¼-watt that red would relate to the main output resistor is associated with each green channel being muted (“stop”) while green LED. These resistors would also have to would relate to the main output channel be unsoldered, removed, and reinstalled. being active (“go”). It’s possible that these Then the unit would be reassembled and color choices may not meet the needs of tested to confirm that the changes func- all users and applications. For example, tion as desired. it’s reported that one European broad- caster typically uses these two colors in For additional information about chang- the opposite fashion. Their choice is to ing the LED colors, please contact Studio have the red LED lit whenever the main Technologies’ technical support. output channel is active, warning the talent that they are “on-air.” The green LED Travel Case is lit whenever the main output channel For portable applications it may be desir- is muted, indicating to the talent that it’s able to store and transport each Model “safe” to say whatever they wish, about 212 in a protective case. After much travel whomever they wish to say it about! with prototype announcer console units, Studio Technologies’ personnel learned For consistency, the LED associated with to appreciate the Pelican Model 1450 the talkback button was selected to be case. Purchased with the foam interior green. This lights whenever the talkback option, it does an excellent job of holding channel is active. It’s possible that some one Model 212, its associated 24 volt DC applications may benefit from revising power supply, and documentation. Some this LED color too. While red is certainly applications may benefit from selecting a one possible choice, other colors are also larger case that would also hold a related a possibility including amber, orange, or headset, cables, etc. A larger case could

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 28 also be selected that would hold multiple For balanced audio sources the mating Model 212 units. Pelican sells their prod- connector (3-pin male XLR-type) should ucts through a dealer network, many of be wired so that signal high (+ or hot) is which can be located via a web search. connected to pin 2, signal low (– or cold) is connected to pin 3, and shield is con- Connecting Analog Inputs nected to pin 1. Unbalanced sources The Model 212 is designed to directly con- should be wired so that signal high is on nect with digital audio signals. However, pin 2, and signal low/shield is connected there may be applications where it would to both pins 1 and 3. If this results in hum be useful to also be able to connect ana- on the input, try connecting signal high to log line-level audio sources. To facilitate pin 2, signal low/shield to pin 3, and pin 1 this one or two line input cards can be left unterminated (“floating”). installed. They are mounted into the spare Several things are worth mentioning when connector locations that are provided on it comes time to actually using a line input the Model 212’s back panel. Two types of card. The input is transformer coupled line input cards are available from Studio with a nominal input impedance of 10 k Technologies and are purchased sepa- ohms. Capacitors in series with the trans- rately. One card contains passive circuitry, former’s primary provide protection again including a 3-pin female XLR-type connec- accidental connection to a signal that has tor and a 10 k ohm to 10 k ohm isolation DC voltage present on it. The nominal transformer. Once installed, balanced or input level is +4 dBu but should work cor- unbalanced line-level audio sources can rectly with signal levels down to nominal be directly connected. The second type –10 dBu. of card contains an identical connector and isolation transformer circuit, followed Note that if one or two line input cards by a sophisticated VCA-based limited are installed in a Model 212, both analog circuit. This arrangement helps prevent line-level audio signals and a digital au- abnormally large signal levels from reach- dio circuit can be connected at the same ing the headphone output channels. time. The audio sources will be routed to the headphone outputs by way of the Each line input card kit contains a printed headphone source configuration switches. circuit board assembly, the required in- Each of the four possible audio sources terconnecting cables, and hardware. To can be routed to the left-headphone out- install the kit is very simple. The XLR-type put, the right-headphone output, or both connector is mounted into one of the headphone-output channels. Details on spare connector locations on the Model how to use these switches are provided 212’s back panel. This secures the con- in the Configuration section of this user nector and associated printed circuit guide. board to the enclosure. The interconnect- ing cables are then used to link the card Additional Connectors with the Model 212’s main printed circuit Two spare connector locations are provid- board assembly. ed on the Model 212’s back panel. From the factory they contain blank plates that can be readily removed and replaced with

Issue 2, June 2006 Model 212 User Guide Page 29 Studio Technologies, Inc. a variety of XLR-type connectors. These This was accomplished by including spare connector locations are specifi- numerous 3-position male “header” con- cally included so that a Model 212 can nectors on the Model 212’s circuit board. be customized to meet the many specific These headers, on 0.1-inch centers, are needs that arise in broadcast and related wired in parallel with the Model 212’s con- audio applications. Expected uses for nectors. This “no solder” solution makes these locations include adding a 5-, 6-, or customizing a Model 212 a simple pro- 7-pin XLR-type connector to allow direct cess. The headers, located on the Model connection of a broadcast headset. In ad- 212’s printed circuit board, are Molex® dition, Studio Technologies offers optional part number 22-23-2031. They mate with line input cards that mount directly in a Molex housing number 22-01-3037. To spare connector location. This was previ- make the interconnection separate crimp ously described in this user guide. terminals are attached to loose wires and then “snapped” into the housing. Molex The spare connector locations are com- part number 08-50-0114 specifies crimp patible with the Neutrik DL-series of terminals that are appropriate for wires of connectors. For flexibility, versions are 22 to 30 gauge. These parts are available available that provide from three to seven worldwide from sources such as Digi-Key contacts. For example, a compatible 3-pin (www.digikey.com). female connector would be Neutrik part number NC3FD-L-1. To support headsets To make the process of connecting to the the NC6FDS-L-1 is often used. This is a Model 212’s headers a simple task an 6-pin female connector with the unique interface cable kit, part number 31087, is Switchcraft® 6-pin arrangement. The available from Studio Technologies. Each hardware that secures the blank plates to kit includes five cable assemblies and a the Model 212’s back panel is also intend- length of heat-shrinkable tubing. Each ed to secure the replacement connectors. cable assembly consists of a mating connector with three color-coded wires at- If connectors are installed in the Model tached. These wires, nominally 12 inches 212’s spare connector locations adding in length, allow convenient soldering to labels to those connectors can be helpful. a connector selected to be installed in a For a great look it is recommended that spare location on the Model 212’s back Brother® P-Touch ¼-inch (6 mm) labels panel. For reference, the wire color for pin be created. Tape material that prints white 1 is gray, pin 2 is yellow, and pin 3 is blue. text on a black background works out well for the Model 212. The Brother label The heat-shrinkable tubing is provided so cassette number TX-3151, white on black, that connector solder cups can be insu- is appropriate for use with many of their lated from each other. It will also provide printers. some strain relief to the solder joints. Be certain to slip the desired length of tubing In addition to the spare connector loca- over the wire prior to soldering a connections on the back panel, provision has tion! (If the writer had a dollar for every been made to allow easy interconnection time he forgot to put tubing on a wire—or with the Model 212’s printed-circuit-board- slip on a connector shell—before making mounted input and output connectors. a solder connection…)

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 30 The Model 212’s enclosure must be disas- Additional functions can be accessed sembled prior to installing connectors in using these 3-position headers: the spare locations. Four hex-head ma- P6: Auxiliary relay contact B, pin 1 normal- chine screws, two on the bottom front of ly closed, pin 2 common, pin 3 normally the enclosure and two on the back panel, open. must be removed. A 5/64-inch hex driver is required. The cover can then be care- P8: AES3 output, pin 1 common, pin 2 fully separated from the chassis, remain- high, pin 3 low. ing attached by means of a flexible cable P9: AES3 input, pin 1 common, pin 2 high, assembly. This “flex-cable” assembly links pin 3 low. the main printed circuit board assembly with the board assembly that contains the P11: Auxiliary relay contact A, pin 1 pushbuttons and LED indicators. Ensure normally closed, pin 2 common, pin 3 that the flex cable is not damaged while normally open. the Model 212 is being customized. For P12: Auxiliary input 2, pin 1 common, easier access, the pushbutton/LED board pin 2 unbalanced analog audio, –10 dBu assembly can also be easily removed. nominal, pin 3 not used. The 3-position headers on the Model P13: Analog mic output, pin 1 common, 212’s main circuit board assembly are pin 2 unbalanced analog audio, –15 dBu generally located close to their related nominal, pin 3 not used. input or output connectors. The following list provides the printed circuit board refer- P14: Auxiliary input 2, pin 1 common, ence numbers and associated functions: pin 2 unbalanced analog audio, –10 dBu nominal, pin 3 not used. P1: AES3id input, pin 1 floating, pin 2 signal, pin 3 shield. P15: Pushbutton backlighting, pin 1 common, pin 2 button lamps, pin 3 current P2: Bidirectional Digital Interface, pin 1 limited 24 volts from external 24 volt DC floating, pin 2 signal, pin 3 shield. input. P3: External 24 volt DC input, pin 1 P17: Remote switch connections, pin 1 common, pin 2 +24 volts, pin 3 not used. common, pin 2 main output control, pin 3 Note: header P10 is used by the back- talkback output audio. panel 24 Vdc jack assembly and is electrically in parallel with P3. Pushbutton Backlighting P4: Headphone output, pin 1 common, For special applications, provision has pin 2 left (tip), pin 3 right (ring). been made to allow illumination (“back- P5: Microphone input, pin 1 shield, pin 2 lighting”) of the two pushbutton switches. high, pin 3 low. Note: follows back-panel This may prove useful for applications 3-pin female XLR pin assignment. where adequate room lighting is not available. It can also serve in custom Model P7: AES3id output, pin 1 floating, pin 2 212 configurations. Note that this is an signal, pin 3 shield. advanced feature, intended only to be implemented by a qualified technician.

Issue 2, June 2006 Model 212 User Guide Page 31 Studio Technologies, Inc. From the outset several limitations must both lamps. Pin 2 of the header is con- be discussed. The first is that button nected to the other contact on both lamps. backlighting is not intended to serve tally Pin 3 is connected, by means of a current applications. (A common connection to limiting resistor, to the external 24 volt power both lamps is provided; indepen- DC source. If lamps were obtained from dent access to the lamp connections on Studio Technologies then adding a “jump- each button is not provided.) It is strictly er” from pin 2 to pin 3 is all that is required intended to provide a moderate amount of to get things going. A standard 0.1-inch- illumination to the button’s clear lens and center jumper, commonly used on elec- associated labeling. The second restric- tronic equipment, is all that is required. A tion is that power for the backlighting func- 390 ohm, 1 watt resistor is electronically tion is in addition to the 150 milliamperes in series between the external 24 volt DC required for normal Model 212 operation. input and pin 3 of the header. When used This should not prove to be a problem with the lamps available from Studio Tech- as the lamps only add approximately 40 nologies, the resistor limits the lamp cur- milliamperes. But it must be taken into rent to approximately 40 mA. This lights account when determining if the power the lamps to a moderate intensity. If a source can support the increased load. different type of lamp is installed, its power source should be connected to pins 1 From the factory, lamps (“bulbs”) are not (common) and 2 (lamps) of the header. installed in the pushbutton housings. They are pluggable T-1 bi-pin type and Remote Control Connections are simple to install. The mating socket is accessed by removing the button’s lens Provision has been made on the Model caps, graphic label, and back frosted 212’s printed circuit board assembly to lens. Compatible incandescent lamps with allow external switches or contact closures a nominal rating of 18 volts, 28 mA are to control the main output and talkback available from Studio Technologies (part output functions. A 3-position header, la- number 12030). Bulbs with other nominal beled P17, provides access to the circuitry voltages should also be available from associated with the functions. Pin 1 of the electronics parts vendors. While compat- header is connected to the common point ible LED-based lamps are probably also of the Model 212’s circuitry. Pin 2 of the available, incandescent lamps, when pow- header is connected to the circuitry asso- ered below their rated current and voltage, ciated with main output pushbutton. Pin 3 can provide extremely long and reliable of the header is connected to the circuitry operation. associated with the talkback output pushbutton. The input circuitry is “active low,” A 3-position header connector, labeled with a 10 k ohm resistor connected to P15, is located on the Model 212’s main +5 volts acting as a pull up. A combina- printed circuit board. It provides access tion of resistors and capacitors provides to, and a means to power, the two lamps. ESD protection. A qualified technician can Pin 1 of the header is connected to the use these inputs for special applications. common point of the Model 212’s circuitry, Contact the factory for additional details. which is also connected to one contact on

Model 212 User Guide Issue 2, June 2006 Studio Technologies, Inc. Page 32 Digital Audio Outputs As has been previously discussed in this user guide, the Model 212 is capable of supporting three digital audio outputs. Directly accessible on the back panel are the BNC connectors for the AES3id output and the bidirectional interface. Accessible internally for installer-selected applications is the AES3 output. It’s important to men- tion that these three outputs are always active, each sending out the identical digital audio and control bit stream. While most applications will use only one of the outputs, there’s no reason why two, or all three, can’t be utilized. In addition, while the bidirectional digital interface is intended to send and receive data over a single cable, it can be used as a standard AES3id output. The only requirement is that the configuration for the digital input source must be selected for something other than the bidirectional digital interface. This ensures that a stable clock source will be available for the all the digital outputs. Channel Status Bits Following the AES3 and AES3id standards, the Model 212 configures the channel status bits. The unit is defined as being a professional device, the sample rate is set to follow the actual sample rate, and the word length is 24 bits. These settings are made in the Model 212’s software and cannot be changed in the field. This was specifically done to help ensure reliable operation in the field. The setting was carefully selected to allow reliable operation in all intended Model 212 applications.

Issue 2, June 2006 Model 212 User Guide Page 33 Studio Technologies, Inc. Microphone Input/Preamplifier: Specifications Type: electronically balanced General Audio: Input Impedance: 2 k ohms, nominal Frequency Response: < –0.1 dB at 20 Hz, –1 dB Gain Range: 10 to 50 dB, nominal, adjustable in at 18 kHz, mic in/main channel out 10 dB steps Distortion (THD+N): 0.025%, measured at 1 kHz, Compatibility: dynamic or phantom-powered mics mic in/main channel out Phantom Power: 48 Vdc, nominal, meets IEC 61938 S/N Ratio: 71 dB, referenced to –46 dBu mic Compressor: in/–14 dBFS out Threshold: –14 dBFS or –4 dBFS, switch selectable Common Mode Rejection Ratio: 68 dB at 60 Hz Attack/Release Time: 2 mSec/100 mSec, nominal Connectors: Slope: 5:1, nominal Mic In: 3-pin female XLR-type Status LED: compressor active AES3id Out, AES3id In, Bidirectional Interface: 75 ohm BNC Headphone Output: 1, stereo Headphone Out: ¼-inch 3-conductor phone jack Compatibility: intended for connection to mono or stereo headphones or headsets with nominal 24 Vdc Power In: coaxial power jack, 2.1 x 5.0 mm, impedance of 100 ohms or greater locking bushing, compatible with Switchcraft S760K plug, center pin positive Type: voltage driver Maximum Output Voltage: 8 Vpp, 150 ohm load Spare Connector Locations: 2 Allows one or two Neutrik NC*D-L-1 connectors to Auxiliary Relay: be installed (*=3F, 3M, 5F, 5M, 6F, 6FS, etc.). Also Function: software configurable compatible with Neutrik EtherCon. Contacts: 2, form C (Common, Normally Closed, Digital Inputs/Outputs: Normally Open) A/D, D/A Converters: 24 bit, 100 dB dynamic range Rating: 1 A, 30 W (resistive) Sampling Rate: internal clock source 48 kHz, exter- Access: requires user-implemented connector nal clock source 32 to 96 kHz scheme AES3id In: unbalanced, transformer-coupled Power Source: Impedance: 75 ohms 24 Vdc nominal, 150 mA max @ 24 Vdc; acceptable Minimum Input Carrier Amplitude: 320 mVpp range 20-30 Vdc. Units shipped to North America (SPDIF compatible) and Japan include a 120 V input/24 Vdc output pow- AES3id Out: unbalanced, transformer-coupled er supply. Units shipped to all other locations include Impedance: 75 ohms a universal input/24 Vdc output power supply. Output Carrier Amplitude (Loaded): 1 Vpp Options: one or two optional cards or connectors Bidirectional: unbalanced transformer-coupled can be installed to provide support for connection Impedance: 75 ohms of AES3, line-level balanced or unbalanced audio Output Carrier Amplitude (Loaded): 1.75 Vpp sources Minimum Input Carrier Amplitude: 320 mVpp AES3 In: balanced, transformer-coupled (via Dimensions (Overall): optional connector) 5.6 inches wide (14.2 cm) Impedance: 110 ohms 3.3 inches high (8.4 cm) Minimum Input Carrier Amplitude: 200 mVpp 8.5 inches deep (22.4 cm) AES3 Out: balanced, transformer-coupled (via Weight: 3.2 pounds (1.45 kg) optional connector) Impedance: 110 ohms Output Carrier Amplitude (Loaded): 3.5 Vpp Features and specifications subject to change without notice.

Issue 2, June 2006 Model 212 User Guide Page 34 Studio Technologies, Inc. Appendix A A label is attached to the security plate on the bottom of the unit. It provides a summary of the configurable parameters and related information. The actual label size 4.25 inches by 4.60 inches.

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Issue 2, June 2006 Model 212 User Guide Page 36 Studio Technologies, Inc.