Headphone Output, Superior Ohm (AES3) Support Also Available

User Guide

Issue 6, July 2015

This User Guide is applicable for serial numbers: M212-01151 and later

50330-0715, Issue 6 This page intentionally left blank. 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

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Issue 6, July 2015 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 Model 212 Announcer’s Consoles with serial numbers of 01151 and later. Addition- al 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, Figure 1. Model 212 front panel and production talent. With its digital audio 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 com- pact system. Some of the unit’s highlights include ease of use, configuration flexibility, and sonic excellence. Figure 2. Model 212 back panel Whether it’s microphone preamplifica- tion, switching of main and talkback audio (AES3id) are standard with balanced 110 signals, or the headphone output, superior ohm (AES3) support also available. audio quality is maintained throughout. A microprocessor provides the Model 212’s While “all-digital” audio installations are logic power, allowing precise control of the getting closer and closer to reality, ana- unit’s operation. A range of choices allows log signals continue to play a role and the desired operating configuration to be will probably do so for many years. As easily selected. While flexible, the user is such, the Model 212 also offers support presented with an easy-to-use set of con- for analog audio inputs, main output and trols and indicators. The digital audio inter- talkback outputs functions. While requiring faces are directly compatible with system the installation of optional connectors or environments that use AES digital audio modules, these analog resources can help signals as their preferred transmission complete specialized applications. method. Unbalanced, 75 ohm interfaces

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 5 A truly next-generation product, extensive routed to the inputs of their respective research into the needs and desires of analog-to-digital converter circuits. The field production personnel was integral to threshold of the compressor can be con- the Model 212’s creation. While primarily figured from among two values. With the targeted for on-air television applications, compressor configured to –14 dBFS some specialized features are included to allow dynamic range control would be expected the Model 212 to be used in a variety of during normal operation. While possibly other audio applications. These include inappropriate for major on-air situations, on-air radio broadcasting, stadium an- having dynamic range control of the nouncement, live production, and voice- signal can offer increased performance over/narration booths. for many applications. This would be appropriate for applications such as stadium announcement positions, sports events System Features using nonprofessional on-air talent, as well as situations where the risk of digital Microphone Input “clipping” is present. When configured A high-performance microphone pre- for –4 dBFS, dynamic range control will amplifier circuit provides low-noise/ only take place as the signal approaches low-distortion amplification over a 10 to the level limit of the digital signal. During 50 dB gain range. The gain is adjustable normal operation the compressor would in 10 dB steps. The input is compatible not be active. with balanced dynamic or condenser microphones. The microphone power Main and Talkback Audio source is 48 volts nominal and meets the Channels worldwide P48 phantom standard. An LED indicator serves as an aid for optimizing Internally, the Model 212 creates analog the setting of the preamplifier’s gain. The main and talkback audio channels. The output of the microphone preamplifier main audio channel is designed to serve is routed to the compressor circuit that as the on-air, stadium announcement, or supports the main and talkback audio other primary audio feed. The talkback channels. audio channel is intended to provide production trucks, control rooms, or sup- Dynamic Range Control port personnel with a talent-originated cue signal. The two analog channels are A studio-quality compressor circuit is converted to 24-bit PCM digital audio and provided to control the dynamic range multiplexed and formatted into an AES of the analog signal coming from the digital audio “stream.” The A/D converters microphone preamplifier. Far from a and digital transmitter circuitry is synchro- simple “clipper,” the circuit utilizes a nized (“locked”) to the selected digital sophisticated laser-trimmed voltage- input signal. If that signal Is not present controlled-amplifier (VCA) integrated cir- the Model 212 will automatically revert to cuit for quiet, low-distortion level control. an internal clock which provides a 48 kHz The output of the compressor is used by sampling rate. The main audio channel is the main and talkback channels, being assigned to digital channel 1 with talkback

Issue 6, July 2015 Model 212 User Guide Page 6 Studio Technologies, Inc. audio assigned to digital channel 2. The powerful when used in a live event applica- composite digital audio signal is routed tion, such as serving as a master console to two physical interfaces. One output is for a production director. AES3id compliant (unbalanced, 75 ohms) By installing optional connectors or mod- with a BNC connector for interfacing. ules analog line-level versions of the main This professional interface is transformer- and talkback output signals are available. coupled and capable of driving long These “click-free” outputs can be useful in broadcast cable runs. applications where both digital and analog The digital audio output signal is also signals are required. routed to a unique bidirectional digital interface. Similar to AES3id, it uses a User Controls and Status BNC connector and supports two chan- Indicators nels of audio in each direction over a single 75 ohm cable. The bidirectional Two pushbutton switches, three LED in- audio interface will find use in specialized dicators, and two rotary controls provide applications, including direct integration the user with a clear, easy-to-use interface. with panel ports on Riedel® intercom One pushbutton switch controls the status systems. Note that audio signals received of the main audio channel. This is the audio from the bidirectional interface are signal intended for on-air, announcement, described in the Cue Sources section or other primary uses. Two LEDs display of this document. the on/off status of the main audio channel. A second pushbutton switch controls the For enhanced flexibility, the Model 212 status of the talkback audio channel. This includes the resources to support a third is the audio signal used to communicate digital output. Circuitry, located on the with producers, directors, spotters, or other printed circuit board assembly, creates an behind-the-scenes production personnel. A AES3 compliant, 110 ohm nominal, trans- status LED is associated with the talkback former-balanced digital output. Gaining button. Two rotary controls allow the user access to this output simply requires add- to adjust the level of the stereo headphone ing a 3-pin male XLR connector to one of output. the two spare connector locations on the Model 212’s back panel. Connector kits, Operational Flexibility available from Studio Technologies, make Much of the Model 212’s unique capabili- this a simple task. ties derive from the ability to configure the The Model 212 isn’t limited for use in “on- on/off control of the main and talkback air” applications. A special feature can be audio channels. To meet the needs of the enabled, placing the unit in a “production” many specific broadcast and production mode. When this mode is active enabling applications, a variety of button operat- the talkback audio channel will no longer ing modes are available. The main button, force the main audio channel to mute. located on the left side of the front panel, This allows the main audio channel to be can be selected to operate from among used as a second talkback output. In this four modes. In the “push-to-mute” mode configuration the unit can be even more the button performs a momentary mute

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 7 of the main audio channel. In this way with standard unbalanced digital audio a “cough” button function is created, signals. The bidirectional digital interface something typically required for television is similar to AES3id but carries two audio sports broadcasting. In the “push-to-talk” channels in each direction. It is intended mode the button provides a momentary for use in special applications. The AES3 active function for the main audio channel. input is balanced, 110 ohms, and to use This mode would be appropriate for appli- requires the addition of a connector on cations such as stadium announcement. the unit’s back panel. No matter which of An alternate action “latching” configura- the digital inputs is selected, the receiver tion allows the button to enable or disable circuitry can accept bit depths of 16 to 24. the main audio channel as desired. This While the nominal sample rate is 48 kHz, is useful in radio broadcasting, announce- any signal in the range of 32 to 96 kHz is booth, or voice-over applications. The acceptable. Note that the received clock fourth mode provides a hybrid function, signal is used for two purposes; it allows supporting both push-to-talk and tap- correct receiver synchronization as well as to-enable/tap-to-disable operation. This serving as the transmitter clock source for operation is similar to that found in many the digital outputs. broadcast intercom system user stations. Digital-to-analog conversion circuitry cre- The button associated with the talkback ates two analog “cue” audio signals from function can be configured to operate the selected digital interface. In on-air from either of two modes. One of the broadcast applications these cue signals, modes supports a “push-to-talk” function. originating in production trailers, control This is typically used for on-air broadcast rooms, or remote locations, supply pro- applications. The other mode provides a gram-with-interrupt audio on one chan- hybrid function, the operation of which is nel and program-only audio on the other. discussed in the previous paragraph. The Each source can be individually assigned hybrid mode is especially useful when the to the left channel, right channel, or both Model 212 is used in a production-support left and right. This allows a wide variety of application. stereo and mono headphone mixes to be created. Headphone Sources Some applications may benefit from being The Model 212 allows two audio channels able to connect analog line-level audio from one of three digital audio sources to signals to the Model 212. To meet this be routed to the stereo headphone output. need one or two optional line input cards Configuration switches select which digital can be installed in the Model 212’s back input is active. The available sources panel. Each card provides a female are the AES3id input, the previously dis- XLR connector and transformer-isolated cussed bidirectional digital interface, and +4 dBu nominal input circuit. Each source the optionally implemented AES3 input. can be individually assigned to the left The AES3id input is an unbalanced, channel, right channel, or both left and 75 ohm interface that uses a BNC connec- right channels of the headphone output. tor. Transformer-coupled, it is compatible

Issue 6, July 2015 Model 212 User Guide Page 8 Studio Technologies, Inc. Headphone Output can provide high output levels with very low distortion and noise, along with minimal Two rotary controls are provided for user current consumption. The output circuits adjustment of the headphone output levels. are configured to safely drive stereo or For application flexibility the actual func- mono loads. This ensures that all types of tion of the two “pots” is configurable. For headphones, headsets, and earpieces can traditional on-air sports applications they be directly connected. can be selected to the dual-channel (“level/ level”) mode which provides independent Audio Quality and Protection control of the left- and right-channel vol- ume. For use with dual-channel cue signals, The Model 212’s circuitry was carefully or to support user preference, the stereo tailored to provide excellent audio perfor- (“level/balance”) mode can be selected. In mance. Professional-quality components this mode one control adjusts the overall are featured throughout. For reliability all level of both the left and right channels, audio routing is performed using solid-state while the other allows adjustment of the devices. In all critical audio paths, “click- left/right level balance. To help minimize the less” performance is provided. All audio chance of broadcast cues being missed, inputs and outputs make extensive use both level control modes can be configured of protection components. This limits the so that a minimum headphone output level chance of damage from ESD and other is maintained. Alternately, the headphone undesirable, yet real-world, hazards. output can be set to fully mute when the controls are at their minimum position. The Power Sources rotary 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. Inside the Model “reversed” to support alternate camera 212, an internal switch-mode power supply angles. By using this special mode intuitive creates the various voltage “rails” required operation will be maintained and a comfort- by the internal circuitry. An external power able work environment assured. supply is included with each unit. Provision has been made to support applications where a monaural cue feed is Relay Contacts desired. A configuration switch allows the Model 212 resources include a general- summing (combining) of the selected left purpose relay, allowing specialized configu- and right headphone sources. In addition rations to be created using its two form-C to creating a dual-channel mono output it (DPDT) contacts. Under software control, also allows the level controls to be config- the relay can be configured to follow the ured as a simple 2-channel mixer. state of the main and talkback audio channels. Taking advantage of the back-panel The stereo headphone output was de- locations provided for additional XLR con- signed to meet the needs of contemporary nectors, a technician may easily implement headphones and headsets. Specifically, the a variety of functions such as providing an output circuits act as voltage, rather than “on-air” indicator or performing loudspeak- power, drivers. In this configuration they er muting during talkback.

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 9 Configuration cable kit allows a Model 212 to be opti- mized to meet the exact needs of specific Model 212 configurations are made using applications. For example, some applica- a number of DIP switches. One 8-position tions may prefer to use a multi-pin XLR switch assembly is used to set the gain connector to interface with a headset. This of the microphone preamplifier, the on/off can easily be accomplished by adding status of phantom power, the compressor the appropriate 5-, 6-, or 7-pin XLR con- threshold, and the headphone stereo/ nector and making a few simple connec- mono mode. Another 8-position switch tions. Other applications may benefit from assembly configures which of the audio having “mult” or “loop-through” connec- sources is routed to the headphone out- tions, something easily incorporated into a put. A 12-position switch assembly com- Model 212. One or two optional line input municates the desired operating modes cards, as previously discussed, can also to the microprocessor. All switches are be mounted in the spare XLR positions. accessible via the bottom of the Model Line output cards are available to support 212’s enclosure; the unit does not have to the analog line-level main and talkback be disassembled. Changes made to any outputs. of the configuration parameters become active immediately. To prevent access to the configuration switches a security plate included with each unit, is attached to the Installation and bottom of the enclosure. Setup Connectors In this section interconnections will be made using the input and output con- The Model 212 uses standard connec- nectors located on the Model 212’s back tors throughout. The microphone input panel. A microphone signal is interfaced uses a 3-pin female XLR connector. The by way of a 3-pin XLR connector. A ¼-inch digital audio inputs and outputs use BNC 3-conductor phone jack is provided for connectors. A ¼-inch 3-conductor jack is the headphone output. Digital audio input used for the headphone output. The ex- and output connections are made using ternal source of 24 volt DC power is con- BNC jacks. A 2.1 x 5.5 mm coaxial jack al- nected by way of a 2.1 x 5.5 mm “locking” lows connection of the external 24 volt DC coaxial power jack. power source. Depending on the installed In the world of broadcast and production options, other connectors may also be audio it’s fair to say that applications vary used to connect analog, digital and power widely. To this end, one or two additional signals. XLR connectors can easily be mounted into the Model 212’s back panel. Multiple System Components 3-position “headers” located on the Model The following are included in the shipping 212’s circuit board provide technician- carton: Model 212 Announcer’s Console, access to all input and output connec- user guide, button label sheet, and 24 volt tions. Using a factory-available interface DC power supply.

Issue 6, July 2015 Model 212 User Guide Page 10 Studio Technologies, Inc. Microphone Input the Model 212. Note that adding the suffix “-XQ” to the headset’s part number (HMD The Model 212 is compatible with bal- 26-600-XQ) specifies a 3-pin male XLR anced dynamic and condenser micro- connector for the dynamic microphone and phones. Depending on the application, a ¼-inch 3-conductor plug for the stereo the microphone may be part of a headset, headphones. This configuration is very or be an independent handheld or stand- useful, allowing the headset to work direct- mounted model. The Model 212’s 48 volt ly “out of the box” with the Model 212. nominal power source will support essentially 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 man- sets, which he did by the veritable “boat- ufacturers such as AKG, Beyer, DPA, Neu- load.” Why? Because these usually broke mann, Sennheiser, and Shure will perform soon after going into service! He knew 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 the beginning, purchased only premium- by way of a 3-pin female XLR 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 coming devices with a nominal impedance mon/shield is connected to both pins 1 of 100 ohms or greater is preferred. This and 3. shouldn’t be an issue since essentially all contemporary devices already meet this The Model 212 is not compatible with condition. unbalanced “electret” microphones that require a source of low-voltage DC for op- Devices are connected to the headphone eration. These microphones, sometimes output by way of a ¼-inch 3-conductor found in low-cost headsets, are not gener- phone jack located on the Model 212’s ally suitable for on-air or other demanding back panel. As is standard for stereo head- applications. phones, 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 HMD 26 headset is very “ring” lead of the jack. Common for both popular for on-air sports broadcasting channels is connected to the “sleeve” lead. use. A fine product, it works very well with

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 11 Devices with ¼-inch 2-conductor “mono” internal clock source will automatically plugs can also be used with the Model be selected. The exception is when the 212’s headphone output. In this arrange- bidirectional digital interface is selected ment only the tip lead (left channel) will as the input source. In this case a valid be active. The 2-conductor plug will signal must be connected to the bidirec- physically connect (“short”) the ring lead tional digital interface for proper digital (right channel) to the sleeve lead (com- audio output signals to be created; in this mon). Technically this won’t damage the configuration the Model 212 will not be circuitry associated with the right-channel able use its internal clock source. headphone output. (50 ohm protection The main output channel is intended to resistors are electrically in series with the be the “on-air” signal that connects to an headphone output circuits.) However, input channel of an audio console. The energy will be wasted if an audio signal talkback output channel is intended for coming out of the right channel goes into connection to control rooms, production a “dead short.” There is a simple solution trailers, or other locations where talent- to this issue. No audio source should be originated voice cues are required. The assigned to the right-channel headphone nominal level of the digital audio signals output. Refer to the Configuration section is –20 dBFS. The actual levels will depend of this user guide for details. on the gain setting of the microphone Unbalanced Digital Audio preamplifier, sensitivity of the microphone, how loudly the talent speaks into the mi- Output crophone, and the configuration setting The main and talkback audio channels of the compressor threshold. are accessible by way of an AES3id unbal- Talkback audio is also “on-air” quality, anced digital audio output. A BNC con- which makes sense since the audio path nector, located on the back panel of the is shared by the talkback and main out- Model 212, provides access to the trans- put channels. Devices connected to the former-coupled interface. This type talkback output channel can range from of digital audio interface is commonly amplifiers associated with loudspeakers used for broadcast applications, providing to inputs on digital matrix intercom a 75 ohm unbalanced implementation of systems. Connecting the talkback output the AES 2-channel digital audio standard. channel to devices that allow easy control The Model 212’s interface provides 24 bit of the signal level can be helpful. For ex- audio signals with a default sample rate ample, connecting to a spare input chan- of 48 kHz. The main output audio signal nel on a digital audio console will provide will be present on channel 1 of the digital the resources to add gain or attenuate the audio signal; talkback audio will be pres- signal as required. A talkback-associated ent on channel 2. output path on the audio console can then The clock (timing) source for the digital connect to the final destination(s). audio output is derived from the selected digital audio input. Should the input source not be present the Model 212’s

Issue 6, July 2015 Model 212 User Guide Page 12 Studio Technologies, Inc. Optional Balanced Digital For the AES3id input to be active a configuration setting must be correctly made. This Audio Output topic is discussed in detail in the configu- Circuitry contained within the Model 212 ration section of this user guide. It’s also allows a technician to add support for an important to note that the selected digital AES3 balanced digital audio output. This input source will also serve as the clock type of interface allows two channels of source for the Model 212’s digital outputs. digital audio to be carried over a balanced 110 ohm circuit. In some Model 212 ap- Optional Balanced Digital plications the AES3 output will be imple- Audio Input mented using a 3-pin male XLR connector installed in the back panel. Other applica- Circuitry contained within the Model 212 tions may use a multi-pin connector, such allows a technician to add support for an as the Neutrik® EtherCon® version of the AES3 balanced digital audio input. This 8-pin RJ45 jack. type of interface allows two channels of digital audio to be received over a bal- The signal coming out of the AES3 out- anced, transformer-coupled, 110 ohm put will be identical to that coming out the circuit. In some Model 212 applications Model 212’s AES3id output. The same the AES3 input will be implemented using content will be transmitted at the same a 3-pin female XLR connector installed in bit depth and clock rate. For full isolation the back panel. Other applications may use separate circuitry, including a matching a multi-pin connector, such as the Neutrik transformer, is provided for each of the EtherCon version of the 8-pin RJ45 jack. two outputs. As with the AES3id input, for the AES3 in- Unbalanced Digital Audio put to be active the appropriate configuration DIP switches must be set. And as with Input the AES3id input, in additional to providing The AES3id input can be used to connect audio sources for the stereo headphone unbalanced digital audio signals to the output, the AES3 input will also serve as Model 212. The two audio channels associ- the clock source for the Model 212’s digital ated with the interface can serve as sourc- outputs. es for the stereo headphone output. The input, physically a BNC connector located Bidirectional Digital Audio on the Model 212’s back panel, allows a Interface depth of up to 24 bits to be supported; however, anything in the range of 16 to 24 The Model 212 includes a bidirectional bits will work correctly. The input is “self- digital interface for use in special applica- clocking” so that compatibility with virtually tions. Using a single 75 ohm, unbalanced any AES3id source should be possible. It’s connection, two channels of digital audio expected that in most cases the Model 212 can be both sent and received. The two will be used in professional audio environ- channels of receive audio can be used ments where the sample rate will be 48 as cue sources for the stereo headphone kHz. However, any source with a sample output. Bit depths of up to 24 and sample rate from 32 to 96 kHz will work correctly. rates of 32 to 96 kHz are supported. For

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 13 the bidirectional digital interface to be jack is the positive (+) connection. While active the appropriate configuration DIP the requirement for the external source is switches much be set. nominally 24 volts, correct operation will take place with any source within the range The ability of the bidirectional digital inter- of 20 to 30 volts. A maximum current of 150 face to send and receive digital audio sig- milliamperes at 24 volts DC is required. nals over one cable makes interconnecting the Model 212 with other equipment in- Included with each Model 212 is a 24 volt credibly simple. For example, the bidirec- DC external power supply. The power tional digital interface is directly compatible supply’s DC output cable has been termi- with panel ports on a Riedel Artist® digital nated with a Switchcraft® S760K coaxial matrix intercom system. A single cable power plug. This “locking” type of plug cor- is all that is required to interface an Artist rectly mates with the Model 212’s 24 Vdc digital panel port with the Model 212. input jack. The locking feature is important, allowing the external power source to be Optional Analog Audio Inputs securely attached to the Model 212. While the Model 212’s headphone sources were designed primarily to be supplied Pushbutton Labeling using one of the digital audio inputs, it’s The two pushbutton switches used in the also possible to connect one or two analog Model 212 were selected for several rea- line-level audio sources. Please refer to the sons. Foremost was the fact that they are Technical Notes section of this user guide highly reliable, using gold-plated contacts for details. for long life in less-than-ideal environments. A second reason was that applying cus- Optional Analog Audio tomized labels to the button caps would Outputs be very simple. The labels, text printed on clear material, are placed under the clear In most cases the Model 212 will be used caps on the top of the buttons. in applications where the main and talkback audio output signals are required to From the factory the left button is labeled be in the form of digital audio outputs. It’s COUGH and the right button is labeled also possible that an application can ben- TALKBACK. This was selected to be appro- efit from having analog live-level versions priate for many on-air applications in Eng- of these signals. This is possible using lish-speaking locations. But it’s expected optional output modules or connectors. that these may need to be changed to meet Please refer to the Technical Notes section the needs of specific applications. of this user guide for details. As a “head start” for some applications, a clear sheet with a number of commonly External Power Input used button designations printed on it is The Model 212 requires an external source included in the shipping carton. These were of 24 volt DC power for operation. It is con- created at the factory using a standard nected by way of a 2.1 x 5.5 mm coaxial personal computer graphics program and power jack that is located on the back laser printed onto 3M CG3300 transparency panel of the unit. The center pin of the film. The desired button labels can be cut

Issue 6, July 2015 Model 212 User Guide Page 14 Studio Technologies, Inc. out with a pair of scissors or an X-ACTO® To prevent unauthorized personnel from knife following the printed guide lines that changing the configuration settings, a indicate the required size. security plate is attached to the bottom of the Model 212’s enclosure. For conve- The clear lens on top of each button cap nience, a settings guide is laser etched can be removed with a fingernail or small into one side of the security plate. It pro- screwdriver. Be certain not to scratch the vides a summary of the configurable pa- button if a screwdriver or other small tool rameters and related information. Refer to is used. The clear label can be removed Appendix A for a representative view of the and replaced. The button cap is then text. The security plate is held in place by snapped back into the top of the button means of four rubber bumpers (“feet”) that housing using finger-pressure only. No have built-in screws. Using your fingers, tool is required to replace the button cap. remove the four bumpers so that the plate If you need to make your own labels the can be removed. Refer to Figure 3 for a process is quite simple. Use a personal detailed view of the configuration switch computer to create the desired text. The assemblies. finished label size should be 0.625-inches (15.8 mm) square. The completed artwork can then be printed on transparency film sheets using a laser or inkjet printer. These sheets are readily available from most office supply stores. A pair of scissors or an X-ACTO knife will complete the task. Configuration For the Model 212 to support the needs of specific applications a number of operating parameters must be configured. These include microphone preamplifier gain, phantom power on/off, headphone cue source selection, headphone stereo/mono mode, and a number of operating modes. Two 8-position and one 12-position DIP switch assemblies are used to establish the desired configuration. These switch assemblies are referred to as Switch 1, Switch 2, and Switch 3, with individual switches designated as SW1-1, SW1-2, etc. The switch assemblies are accessed through openings in the bottom of the Model 212’s enclosure. The enclosure Figure 3. Bottom view of Model 212 showing does not have to be disassembled to configuration switches and compressor active LED gain access to the switches.

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 15 Microphone Preamplifier Gain, Phantom Power, and Compressor Threshold 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. Another switch selects the threshold level of the compressor circuit. 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, Figure 4. Microphone preamplifier gain switch 50 dB; 0 dB (no gain) is also available. settings Only one switch should be enabled at a time. There’s no problem changing the output sensitivity of the connected micro- gain setting while the unit is operating. phone and the acoustical output level of Audio clicks or pops might occur during the microphone’s user. With some headset gain transitions, but this shouldn’t be a microphones, such as the Sennheiser major issue as long as associated monitor HMD 26, selecting an initial setting of 30 loudspeakers are temporarily attenuated dB is appropriate. Users who speak loudly or muted. might need to have the gain reduced to 20 dB. Quiet users might need 40 dB of gain. Selecting the correct amount of gain for an application might take a little experimenta- An LED indicator is provided as an aid tion. The goal is to bring the mic’s signal in correctly setting the gain of the micro- up so that the main and talkback output phone preamplifier. Red in color, this LED levels will match the Model 212’s nominal is located adjacent to switch assembly 1. digital output level which is –20 dBFS. It is visible by observing the bottom of the Operating at this signal level will help to Model 212’s enclosure when the security ensure the delivery of “clean” audio with plate has been removed. Technically, this adequate level “headroom.” red LED lights whenever the compressor circuitry is controlling the dynamic range The output of the Model 212’s microphone of the signal coming from the microphone preamplifier is used, by way of the com- preamplifier. Using configuration DIP pressor circuit, by the main and talkback switch SW1-7, the compressor’s thresh- outputs. So creating a nice “hot” signal old will be set to either –14 or –4 dBFS. will help maintain audio quality, specifically (Details concerning setting the compress a high signal-to-noise ratio. threshold are discussed later in this user Unfortunately, there’s no “perfect” gain guide.) If the threshold is set for –14 dBFS setting that this guide can recommend. a good “rule of thumb” is to adjust the The two issues that impact the setting are gain of the microphone preamplifier such

Issue 6, July 2015 Model 212 User Guide Page 16 Studio Technologies, Inc. that the compressor active LED will light Phantom Power (“flash”) only when the connected micro- The Model 212 can provide 48 volt nomi- phone is sending signal peaks. During nal phantom power to the connected normal operation the LED should never microphone. Switch SW1-8 controls remain fully lit when audio of typical signal whether or not phantom power is active. level is present on the mic input. By phantom power’s very nature it could If the threshold is set for –4 dBFS the LED be left applied to the microphone input at should light only on extreme signal peaks, all times. But generally people prefer to or possibly never. This is because with turn it off unless it is required for a specific a –4 dBFS threshold the compressor is microphone. intended only to prevent signals from ever causing the maximum digital level of 0 dBFS to be reached. It’s not supposed to reduce the dynamic range of normal program material. As an aid in setting the microphone preamplifier’s gain, it might be useful to temporarily set the compressor’s threshold to –14 dBFS. Once the gain has Figure 5. Phantom power switch settings been set so that the LED lights only on peaks the threshold can be returned to Compressor Threshold the –4 dBFS setting. An analog audio compressor circuit is It’s expected that the 10 and 50 dB gain provided to control the dynamic range of settings will not often be used. But there the signal coming from the output of the are always exceptions and that’s why they microphone preamplifier. Switch SW1-7 were included. It’s possible that with a is used to select the threshold (level) at very “hot” microphone, such as a phan- which the compressor circuit will actively tom-powered condenser-type, 10 dB of begin controlling the signal’s dynamic gain could be correct. It’s also possible range. Two choices are available, –14 or that a microphone with a very low-level –4 dBFS, which refer to the signal level output, such as a ribbon-type, would need in dB below the maximum digital output 50 dB of gain. But in general, the 20, 30, level. (The maximum level of a digital au- and 40 dB gain settings will serve most dio signal is typically referred to as 0 dBFS applications. with FS indicating full scale or all bits being “1”s.) Setting the threshold for –14 Note that if no gain switch is set to its dBFS would provide 6 dB of level above active (on) position the preamplifier will operate at unity (0 dB) gain. With a microphone connected as the input source one should never use the 0 dB setting. The issue is that with no gain added to the microphone input signal, the relative noise floor on the main and talkback output channels will be much too high. Figure 6. Compressor theshold switch settings

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 17 the Model 212’s nominal operating level of –20 dBFS before signal compression would start taking place. This setting is appropriate for most applications. The –4 dBFS setting allows 16 dB of signal above nominal and in this case the compressor would essentially act to prevent signals from reaching digital maximum ( 0 dBFS). “Hard” clipping of a signal by reaching digital maximum will result in very nasty audio performance. Headphone Source Selection Switch assembly SW2 is used to configure the source or sources that are routed to the stereo headphone output. Up to four sources may be available with the choices being digital input channel 1, digital input channel 2, auxiliary input 1, and auxiliary input 2. The digital input channels are provided by the selected digital input source. The digital input source is configured Figure 7. Left and right channel headphone from these choices: the AES3id input, the source selection settings optional AES3 input, or the bidirectional to the Model 212, with an optional line digital interface. The auxiliary inputs are input card installed. Line-level audio from analog and available only if optional line a golf event “spotter” is connected to the input cards have been installed. line input. In a case such as this, it would Each of the available input sources can be be typical for digital input channel 1 to assigned to the headphone output’s left be assigned to the headphone’s left channel, right channel, or both the left and channel, digital input channel 2 assigned right channels. The Model 212’s circuitry to the right channel, and auxiliary input 1 allows any combination of input assign- also assigned to the right channel. This ments to be made. For example, consider would allow both digital input channel the situation where a single digital input 2 and “spotter” audio to be heard in the channel is actively connected to the Model headphone’s right-channel output. To 212. In this case it may be desirable to achieve this would require that switches assign this signal to both the left and right SW2-1, SW2-6, and SW2-7 be placed in headphone channels. This would entail their on positions. Note that using another setting switches SW2-1 and SW2-5 to their Studio Technologies 200-series announc- on positions. All other switches would er’s console at the “spotter” location could remain in their off positions. also prove effective. It would provide all the necessary microphone preamplifier, A more complex application might have a talkback routing, and headphone monitor- 2-channel digital audio signal connected ing resources.

Issue 6, July 2015 Model 212 User Guide Page 18 Studio Technologies, Inc. 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 to the user’s right ear, and vice versa. A specific application where this can oc- Figure 8. Headphone output mode settings cur is when on-air talent needs to have a headset’s boom microphone come across the two front-panel user level controls the right side of their face, rather than the (“pots”) can be used to create the desired more-typical left side. In this case it’s im- “mix” of signals being sent to the head- portant to select the left- and right-channel phone output. Many applications, especially headphone source assignment accord- in production settings, can benefit from this ingly. With the Model 212’s flexible source capability. The desired cue sources must selection there’s no reason why users, be carefully assigned to take advantage of such as on-air talent, shouldn’t have their the monaural mode. The first cue source cue sources assigned correctly. should be assigned, using the DIP switches, to the left channel. Its output level will There may be cases where a monaural be adjusted by the left control. The second “single-muff” headset or headphone will cue source should be assigned to the right be connected to the Model 212’s head- channel. Its output level will be adjusted by phone output. In this case the desired cue the right control. source(s) should be routed only to the left channel. No sources should be assigned There is one limitation related to the head- to the right channel. This will eliminate the phone mono output mode. It’s the fact short-circuit current that could occur when that the output will be 2-channel mon- a 2-conductor (monaural) plug is mated aural. Whatever signal is present on the with the Model 212’s 3-conductor (stereo) headphone output’s left channel will also headphone output jack. be present on the right channel. A stereo headphone mix can’t be created. But in Headphone Output Mode most cases this limitation won’t overshadow the benefit of being able to create the mix. Switch SW1-6 allows a monaural head- For signal-flow clarification please review phone output to be created. This is accom- the block diagram located at the end of this plished by summing (adding) the selected user guide. left- and right-channel cue signals. The combined signals are sent to both the left- and right-channel headphone output driver Operating Modes circuits. The outputs of these circuits con- The twelve switches associated with switch nect, by way of 100 ohm series protection assembly SW3 are used to configure the resistors, to the headphone output jack. Model 212’s operating modes. Technically, these switches “talk” to the micro-controller The headphone output monaural mode fea- integrated circuit and associated software ture was specifically included so that a spe- that give the Model 212 its “smarts.” The cial “2-channel headphone mix” mode can software has been carefully designed to be created. By enabling the mono mode,

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 19 provide a number of different ways in which • Hybrid: This mode is a combination of the unit can function. It’s critical to carefully push to talk and alternate action. It’s review the available options and choose similar to the way talk buttons function the ones that best meet the needs of a spe- on user stations associated with broad- cific application. Note that switches can be cast and production intercom systems. changed even while the Model 212 is pow- If the button is pressed and held, the ered up and operating. The unit’s operating main output channel will become active characteristics will change in “real-time” in until the button is released. If the button response to configuration changes. is momentarily “tapped” the main output channel will change state. Upon power Main Output Button Mode up the main output channel will be in its Switches SW3-1 and SW3-2 configure how muted state. the main output button functions. Talkback Output Button Mode Switch SW3-3 configures the way the talkback output button functions.

Figure 10. Talkback output button mode settings Figure 9. Main output button mode settings Two modes are available: There are four available modes: • Push to talk: In this mode the talkback • Push to mute: In this mode the main out- output channel is normally muted (mini- put channel is normally active. The main mum digital audio level). The talkback output channel will mute (have minimum output channel will become active digital audio level) whenever the button whenever the button is pressed and is pressed and held. This is the “cough” held. mode typically used for on-air sports broadcasting applications. • Hybrid: This mode is a combination of push to talk and alternate action. If the • Push to talk: In this mode the main out- button is pressed and held, the talk- put channel is normally muted. The main back output channel will become active output channel will become active when- until the button is released. If the button ever the button is pressed and held. is momentarily “tapped” the talkback • Alternate action: In this mode the main output channel will change state. Upon output channel will change between its power up the talkback output channel active and muted state whenever the but- will be in its muted state. ton is pressed. Upon power up the main output channel will be in its muted state.

Issue 6, July 2015 Model 212 User Guide Page 20 Studio Technologies, Inc. Headphone Output Operating Modes The user is provided with two rotary level controls (“pots”) that are associated with the stereo headphone output. Switches SW3-4, SW3-5, and SW3-6 are used to configure the way the controls function. With just these three switches a wide Figure 12. Headphone control operation range of operating modes can be con- settings figured. Carefully reviewing the capabili- set to the normal mode, and level/level ties of the available functions may prove mode is also selected, the left control ad- worthwhile. justs the level of headphone output’s left Dual-Channel or Stereo Mode channel. (This is the signal that appears on the tip lead of the ¼-inch 3-conductor Switch SW3-4 is used to select whether jack.) The right control adjusts the level the controls provide a dual-channel of the right channel. When selected to (“level/level”) or stereo (“level/balance”) the normal mode, and the level/balance mode of operation. In the level/level mode mode is also selected, turning the balance the two controls operate independently, control in the counterclockwise direction each controlling the level of one of the increases the perceived level of the left headphone output channels. This mode channel output, and vice versa. is generally used for on-air broadcast applications where independent cue As you may have already guessed, when signals are provided to the left- and right- selecting the reverse left/right mode of headphone channels. In the level/balance operation everything is reversed! To be mode the left rotary control sets the overall more specific, when set to reverse mode, output level for both headphone channels. and the level/level mode is also selected, The right rotary control is used to adjust the left control adjusts the headphone the balance (the relative levels) of the left output’s right channel (output jack’s ring and right channels. This mode is generally lead) while the right control adjusts the best suited for applications where a stereo left channel. When selected to the reverse cue source is being provided. mode, and the level/balance is also selected, turning the balance control in the counterclockwise direction increases the perceived level of the right channel output, and vice versa. The reverse mode is provided specifically for cases where a headset’s left and right ear pieces are placed on a user’s head Figure 11. Headphone control mode settings in a reverse orientation. This ensures that Reverse Left/Right Mode the user is provided with a consistent and easy-to-use set of headphone level Switch SW3-5 is used to select whether controls. the rotary controls are in the normal or reverse left/right mode of operation. When

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 21 Minimum Level Mode Digital Input Source Switch SW3-6 is used to conﬁgure the Switches SW3-7 and SW3-8 are used to headphone output’s minimum level. In the select which one of the three digital inter- –40 dB mode the minimum headphone faces will be used by the Model 212 as its output level is 40 dB below maximum. The audio source and reference clock input. headphone output channels will never fully The two audio channels associated with mute. This ensures that any audio signal the selected digital input can be assigned present on the selected cue audio source to the headphone output channels. In ad- will always be present on the headphone dition, the clock signal derived from the output. In most on-air broadcast applica- selected digital input is used by the digital tions this is the appropriate setting. audio circuitry. This clock signal is the master “sync” reference that the Model When the full mute mode is selected, and 212 uses for the analog-to-digital conver- the level/level mode is also selected, mov- sion and digital audio transmission func- ing either control to its fully counterclock- tions. The digital input interface choices wise position will cause its associated are AES3id In, bidirectional digital inter- channel to fully mute. face, and AES3 In. As selecting the correct When the full mute mode is selected, and interface is critical to proper Model 212 the level/balance mode is also selected, operation it’s worth describing each turning the level control to its fully coun- in detail. terclockwise position will cause both The AES3id input is located on the Model headphone channels to mute. Turning the 212’s back panel and is compatible with balance control to either its fully clock- unbalanced 75 ohm digital audio signals. wise or fully counterclockwise position will This type of signal is common to broad- cause the appropriate channel to mute. cast facilities where audio and video Selecting the full mute mode may be utilize a common cabling-type and BNC appropriate for applications where mini- connectors for signal transport. Note that mizing the chance of audio “leakage” many people refer to this generically as is important. This could occur when the an “AES” digital audio signal. This can connected headset or headphones are be confusing but is not inaccurate. Previ- at times placed on a desk or tabletop. ously there were separate standards for

Figure 13. Headphone output minimum level settings

Figure 14. Digital input source settings

Issue 6, July 2015 Model 212 User Guide Page 22 Studio Technologies, Inc. 75 ohm unbalanced (AES3id) and 110 Incorrectly setting the digital input source ohm balanced (AES3) digital audio sig- will probably prove to be the most com- nals. However, that was revised under mon cause of incorrect Model 212 opera- a newer revision of the AES3 standard tion. Carefully reviewing the connected which now covers both balanced and signals and then selecting the appropriate unbalanced implementations. interface will lead to successful operation. The bidirectional digital interface is a Relay Mode special type of 75 ohm unbalanced signal Switches SW3-9 and SW3-10 are used that carries two channels of digital audio to conﬁgure the operating mode of the in each direction. To clarify, over a single auxiliary relay. unbalanced cable two channels of digital audio are sent in one direction and two channels of digital audio are sent in the other. The bidirectional digital interface uses a BNC connector which is located on the Model 212’s back panel. The interface is only appropriate for use in carefully engineered systems that are compatible with this type of signal. An example application is where a Model 212 is directly interfaced with a 75 ohm port on a Riedel digital matrix intercom system. Figure 15. Relay mode settings

AES3 input circuitry is located inside the Three modes are available: Model 212’s enclosure and is compatible with balanced 110 ohm digital audio sig- • Relay is disabled: In this mode the relay nals. This type of signal is typically found is disabled and will never change state. in non-broadcast applications where the • Follows main output status: In this mode use of twisted pair wiring with a maximum the relay will follow the state of the main interconnection length of 100 meters does output channel. Speciﬁcally, the relay not pose a problem. The Model 212 pro- will change state (energize) whenever vides the AES3 input circuitry for installer- the main output channel is active. selected applications where the desired connector is mounted into one of the • Follows talkback button status: In this spare connector locations on the Model mode the relay will follow the state of the 212’s back panel. Many applications use talkback output channel. Speciﬁcally, standard 3-pin female XLR connectors for the relay will change state (energize) AES3 inputs. However, using other con- whenever the talkback output channel nector types, such as Neutrik EtherCon, is active. can be a convenient way of transporting a number of different signals over “CAT5” or “CAT6” twisted-pair cable.

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 23 System Modes Conclusion Switch SW3-12 is used to configure the Once the multitude of DIP switches have overall operating mode of the Model 212. been set to their desired configuration, Specifically, it determines how the main the security plate should be reattached. output channel operates vis-à-vis the The four rubber bumpers should be hand- talkback output channel. Understanding tightened only. No tools should be used. how the two modes impact overall system operation will ensure that correct operation and maximum usability will occur. Operation When the On-Air mode is selected, the At this point the desired input, output, main output channel will mute (minimum and power connections should have been digital audio signal level or –infinity) when- made. The button labels may have been ever the talkback output channel is ac- revised. Finally, the configuration switches tive. The on-air mode should be selected should have been set. Normal operation of for all on-air broadcast applications. It’s the Model 212 can now begin. The unit will imperative that the main output channel begin functioning as soon as the source of be muted whenever on-air talent uses the nominal 24 volts DC is connected. talkback output channel to communicate with production personnel. Upon Model 212 power up, the three status LEDs will light in succession as a When the system mode is set for Produc- firmware “boot up” indication. The unit will tion, the main output channel is never then begin normal operation. Depending muted in response to the talkback output on the selected configuration, one LED channel being active. In this way the main associated with the status of the main out- and talkback output channels can be used put may be lit. The user is now presented independently, with neither impacting the with two buttons, three LEDs, and two other. An example of where this would be rotary controls. These are simple to oper- useful is allowing the Model 212 to provide ate and understand, as will be described two independent talkback functions; the in the following paragraphs. main and talkback buttons can be used independently or simultaneously. The Pushbutton Switches and Production mode can prove very useful when selected for the correct application, Status LEDs but it’s not appropriate for on-air use! Two pushbutton switches are used to control the main and talkback output channels. The way each operates depends on the selected configuration. Three LED indicators are located adjacent to the buttons. They reflect the status of the main and talkback output functions.

Figure 16. System mode settings

Issue 6, July 2015 Model 212 User Guide Page 24 Studio Technologies, Inc. Main Output Button and LED Indicators • Hybrid: This mode is a combination of The button on the left, factory labeled as push to talk and alternate action. It is COUGH, functions according to the se- similar to the way talk buttons function lected configuration. Two LED indicators, on user stations associated with broad- located directly above the button, are as- cast or production intercom systems. If sociated with the status of the main output the button is pressed and held, the main channel. The green LED, located on the output channel will become active until right, is lit whenever the main output chan- the button is released. If the button is nel is active. This could be considered as momentarily “tapped” the main output an “on-air” or mic active indicator. At the channel will change state. Upon Model least it should serve as a “careful what you 212 power up the main output channel say” warning! If the Model 212’s system will be in its muted state. mode is configured to On-Air, the red LED, Main Output vis-à-vis Talkback Activity located on the left, will be lit when the main output channel is muted. This indicates that This short section applies only to the case it’s safe to speak as one sees fit. where the Model 212’s system mode is configured for On-Air and the main output If the Model 212’s system mode is config- button mode is set to alternate action or ured to Production, the red LED will never hybrid. light. This is to reflect the fact that the main output button has now taken on a function Talkback activity will always cause the similar to that of the talkback output button. main output channel to be placed in its To clarify, when the Model 212 is set to the off state. If the main output channel was production mode, the red LED will never in the “latched” on state when talkback light; the green LED will light whenever the began, once talkback activity ends that main output channel is active. state will resume; the main output channel will again be in its on (“latched”) state. Main Output Button Modes Talkback Output Button and LED • Push to mute: If this mode is selected the Indicator main output channel is normally active. The main output channel will mute when- The button on the right, factory labeled ever the button is pressed and held. TALKBACK, controls the talkback output channel. The manner in which the talk- • Push to talk: If this mode is selected the back button functions depends on the main output channel is normally muted. way it was configured. One LED indicator, The main output channel will become green in color, is located directly above active whenever the button is pressed the talkback button. It lights whenever the and held. talkback output channel is active. If the • Alternate action: If this mode is selected Model 212’s system mode is selected to the main output channel will alternate On-Air, whenever the talkback function between its active and muted states is active the main output channel will be whenever the button is pressed. Upon placed in its muted state. If the Model 212 power up the main output channel will is selected to the Production mode, the be in its muted state. status of the talkback output channel will not impact the main output channel.

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 25 Talkback Output Button Modes adjusts the headphone output’s right chan- • Push to talk: If this mode is selected nel. The control on the right adjusts the left the talkback output channel is normally channel. muted. The talkback output channel will When in the level/level mode, and the mini- become active whenever the button is mum output level is set for –40 dB, turning pressed and held. each control to its fully counterclockwise • Hybrid: This mode is a combination of position will place its respective output push to talk and alternate action. If the level 40 dB below its maximum. This set- button is pressed and held, the talkback ting ensures that talent will never be fully output channel will become active un- “isolated” from potentially important cue til the button is released. If the button signals. If present on the Model 212’s input is momentarily “tapped” the talkback and assigned to the headphone channels, output channel will change state. Upon some audio signal will always be present Model 212 power up the talkback output on the headphone output. If set to the full channel will be in its muted state. mute mode, turning each control to its fully counterclockwise position will cause its Headphone Output Level respective output to fully mute. Controls Each level control has a mechanical step (detent) that is located at the halfway Two rotary controls (“pots”) are located (50%) position of its rotation range. This is on the Model 212’s front panel and are as- intended to serve as an aid to Model 212 sociated with the headphone output. The users. In an ideal installation, setting the way the controls function depends on the controls to their detent position will result in selected configuration. One configuration a comfortable headphone output level. The parameter sets the controls to operate in user, in response to a changing operating a level/level or a level/balance mode. An- environment, can then move the level con- other parameter allows the left/right assign- trols to get more or less level as desired. ment of the controls to be reversed. A third The detent position will always remain as parameter selects whether the headphone a useful reference point. To achieve this output channels will maintain a minimum condition the audio levels on the selected output level or can be fully muted. cue sources would have to be adjusted as Level/Level Mode required. This is somewhat counter to the When set to the level/level mode, the two usual mentality of just providing the user controls operate independently. Each con- with whatever level comes up by default. trol sets the output level of one channel of Spending a few extra minutes “trimming” the stereo headphone output. If configured the audio levels can result in much happier, to the normal mode, the control on the left and more productive, talent. side is used to adjust the level of the head- Level/Balance Mode phone output’s left channel. The control on When set to the level/balance mode, the the right is used to adjust the level of the two controls operate together to adjust the right channel. If configured to the reverse desired headphone output level. The con- left/right mode, the control on the left side trol on the left adjusts the overall level of

Issue 6, July 2015 Model 212 User Guide Page 26 Studio Technologies, Inc. both the left and right channels. The bal- will allow the user, in response to their ance control, located on the right, adjusts preference or a changing environment, to the relative left/right level balance. In this adjust the level and balance controls as mode the controls operate in a manner desired. The detent positions will always reminiscent of a consumer audio ampli- remain as a useful reference point. To ﬁer or receiver. If set to the normal mode, achieve this condition the audio level on rotating the balance control in the coun- the connected sources must be adjusted terclockwise direction reduces the level of as required. Spending a few extra minutes the right channel providing the user with “trimming” the connected audio signals, more perceived level in the left channel. rather than just providing whatever hap- If set to the reverse mode, rotating the pens to come up, should prove worth- balance control in the counterclockwise while. The result will be talent that is more direction reduces the level of the left chan- relaxed, and an overall production that nel providing the user with more perceived works more smoothly. level in the right channel. When in the level/balance mode and the minimum output level is set to –40 dB, Technical Notes turning the level control to its fully coun- Phantom Power terclockwise position will place both head- The Model 212 provides a 48 volt nominal phone output channels to 40 dB below source of “phantom power” to support maximum. This ensures that talent will condenser microphones. It’s designed to never be fully “isolated” from potentially meet the P48 requirements as speciﬁed important cue signals. In addition, rotat- in the IEC 61938 standard. The required ing the balance control to either its fully circuitry is very simple: 6.85 k ohm resis- clockwise or fully counterclockwise posi- tors provide a path from a 45 volt source tion will cause the applicable channel to to pins 2 and 3 of the microphone input be 40 dB below its maximum. If set to the connector. The resistors and the power full mute mode, turning the level control source work together to meet the require- to its fully counterclockwise position will ment of 48 ±4 volts, up to a maximum cause both the left and right channels to current of 10 milliamperes. fully mute. In addition, rotating the balance control to either its fully clockwise or fully LED Colors counterclockwise position will cause the applicable channel to fully mute. As previously described, two LED indicators are associated with the main output Each control has a mechanical step and are located directly above the main (detent) that is located at the halfway output pushbutton switch. The red LED, (50%) position of its rotation range. The located on the left, is lit whenever the balance control will typically be set to its main output is muted. The green LED, center, detent position, making the level located on the right, is lit whenever the of the left and right channels equal. In an main output is active. The thought pro- ideal installation, the level control can also cess behind the color choices was that be set to its detent position and provide a red would relate to the main output being comfortable headphone output level. This muted (“stop”) while green would relate to

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 27 the main output being active (“go”). It’s pos- Studio Technologies’ personnel learned to sible that these color choices may not meet appreciate the Pelican Model 1450 case. the needs of all users and applications. For Purchased with the foam interior option, it example, it’s reported that one European does an excellent job of holding one Model broadcaster typically uses these two col- 212, its associated 24 volt DC power sup- ors in the opposite fashion. Their choice is ply, and documentation. Some applications to have the red LED lit whenever the main may benefit from selecting a larger case that output is active, warning the talent that they would also hold a related headset, cables, are “on-air.” The green LED is lit whenever etc. A larger case could also be selected the main output is muted, indicating to the that would hold multiple Model 212 units. talent that it’s “safe” to say whatever they Pelican sells their products through a dealer wish, about whomever they wish to say it network, many of which can be located via about! a web search. For consistency, the LED associated with Connecting Analog Inputs the talkback button was selected to be green. This lights whenever talkback is The Model 212 is designed to directly active. It’s possible that some applications connect with digital audio signals. However, may benefit from revising this LED color too. there may be applications where it would While red is certainly one possible choice, be useful to also be able to connect analog other colors are also a possibility, including line-level audio sources. To facilitate this amber, orange, or blue—these days there one or two line input cards can be installed. are lots of choices available. They are mounted into the spare connector locations that are provided on the Model A qualified technician can easily revise the 212’s back panel. Two types of line input LED colors to meet an application’s exact cards are available from Studio Technolo- needs. The process would begin by disas- gies and are purchased separately. One sembling the Model 212’s enclosure and card contains passive circuitry, including a detaching the pushbutton/LED printed cir- 3-pin female XLR connector and a 10 k ohm cuit board assembly. The LEDs would then to 10 k ohm isolation transformer. Once be unsoldered, removed, and reinstalled (or installed, balanced or unbalanced line-level replaced) in the desired locations. To con- audio sources can be directly connected. trol the LED current and set the brightness, The second type of card contains an iden- a 825 ohm 1206-size surface-mount resistor tical connector and isolation transformer is electrically in series with each LED. circuit, followed by a sophisticated VCA- For additional information about changing based limiter circuit. This arrangement helps the LED colors, please contact Studio prevent abnormally large signal levels from Technologies’ technical support. reaching the headphone output channels. Each line input card kit contains a printed Travel Case circuit board assembly, the required For portable applications it may be desir- interconnecting cables, and hardware. able to store and transport each Model To install the kit is very simple. The XLR 212 in a protective case. After much travel connector is mounted into one of the spare with prototype announcer console units, connector locations on the Model 212’s

Issue 6, July 2015 Model 212 User Guide Page 28 Studio Technologies, Inc. back panel. This secures the connector Connecting to the Analog and associated printed circuit board to the enclosure. The interconnecting cables are Outputs then used to link the card with the Model The Model 212’s circuitry provides unbal- 212’s auxiliary input headers on the main anced line-level outputs associated with printed circuit board assembly. the main and talkback outputs. These are accessible using two 3-pin header connec- For balanced audio sources the mating tors located on the printed circuit board connector (3-pin male XLR) should be assembly. The analog outputs are intended wired so that signal high (+ or hot) is con- for use in applications where it would be nected to pin 2, signal low (– or cold) is beneficial to have, in addition to the digital connected to pin 3, and shield is connect- output resources, signals to interface with ed to pin 1. Unbalanced sources should be the still-popular “analog world.” wired so that signal high is on pin 2, and signal low/shield is connected to both pins Technically the main and talkback analog 1 and 3. If this results in hum on the input, outputs are capacitor coupled and have a try connecting signal high to pin 2, signal nominal level of -2 dBu. They can be used low/shield to pin 3, and pin 1 left untermi- directly, by way of optional connectors that nated (“floating”). would be mounted in the unit’s back panel. This is not optimal as the Model 212’s Several things are worth mentioning when common connection will “leave” the unit it comes time to actually using a line input and possibly be part of the ground hum or card. The input is transformer coupled with noise situation. A line output card kit, avail- a nominal input impedance of 10 k ohms. able from Studio Technologies, will provide Capacitors in series with the transformer’s a transformer-coupled output. One or two primary provide protection again accidental of the cards can be mounted into the spare connection to a signal that has DC voltage connector locations that are provided on present on it. The nominal input level is the Model 212’s back panel. +4 dBu but should work correctly with signal levels down to nominal –10 dBu. A line output card kit contains a printed circuit board assembly, the required inter- Note that if one or two line input cards connecting cable, and hardware. To install are installed in a Model 212, both analog the kit is very simple. The XLR connector is line-level audio signals and a digital audio mounted into one of the spare connector circuit can be connected at the same time. locations on the Model 212’s back panel. The audio sources will be routed to the This secures the connector and associated headphone outputs by way of the head- printed circuit board to the enclosure. The phone source configuration switches. Each interconnecting cable is then used to link of the four possible audio sources can be the card with the Model 212’s main printed routed to the left-headphone output, the circuit board assembly. Refer to the next right-headphone output, or both head- paragraph in the section of the user guide phone-output channels. Details on how for details on which specific connectors to use these switches are provided in the on the main printed circuit board assem- Configuration section of this user guide. bly apply to the main and talkback analog outputs.

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 29 Additional Connectors been made to allow easy interconnection with the Model 212’s printed-circuit-board- Two spare connector locations are provided mounted input and output connectors. This on the Model 212’s back panel. From the was accomplished by including numerous factory they contain blank plates that can 3-position male “header” connectors on be readily removed and replaced with a the Model 212’s circuit board. These head- variety of XLR connectors. These spare ers, on 0.1-inch centers, are wired in paral- connector locations are specifically includ- lel with the Model 212’s connectors. This ed so that a Model 212 can be customized “no solder” solution makes customizing to meet the many specific needs that arise a Model 212 a simple process. The head- in broadcast and related audio applications. ers, located on the Model 212’s printed Expected uses for these locations include circuit board, are Molex® part number adding a 5-, 6-, or 7-pin XLR connector 22-23-2031. They mate with Molex housing to allow direct connection of a broadcast number 22-01-3037. To make the intercon- headset. In addition, Studio Technologies nection separate crimp terminals are at- offers optional line input cards that mount tached to loose wires and then “snapped” directly in a spare connector location. This into the housing. Molex part number 08-50- was previously described in this user guide. 0114 specifies crimp terminals that are ap- The spare connector locations are compat- propriate for wires of 22 to 30 gauge. These ible with the Neutrik DL-series of connec- parts are available worldwide from sources tors. For flexibility, versions are available such as Digi-Key (www.digikey.com). that provide from three to seven contacts. To make the process of connecting to the For example, a compatible 3-pin female Model 212’s headers a simple task an inter- connector would be Neutrik part num- face cable kit, part number 31087, is avail- ber NC3FD-L-1. To support headsets the able from Studio Technologies. Each kit NC6FDS-L-1 is often used. This is a 6-pin includes five cable assemblies and a length female connector with the unique Switch- of heat-shrinkable tubing. Each cable as- craft® 6-pin arrangement. The hardware sembly consists of a mating connector with that secures the blank plates to the Model three color-coded wires attached. These 212’s back panel is also intended to secure wires, approximately 12 inches in length, the replacement connectors. allow convenient soldering to a connector If connectors are installed in the Model selected to be installed in a spare location 212’s spare connector locations adding on the Model 212’s back panel. For refer- labels to those connectors can be helpful. ence, the wire color for pin 1 is gray, pin 2 For a great look it is recommended that is yellow, and pin 3 is blue. Brother® P-Touch ¼-inch (6 mm) labels be The heat-shrinkable tubing is provided so created. Tape material that prints white text that connector solder cups can be insulated on a black background works out well for from each other. It will also provide some the Model 212. The Brother label cassette strain relief to the solder joints. Be certain number TX-3151, white on black, is appro- to slip the desired length of tubing over priate for use with many of their printers. the wire prior to soldering a connection! In addition to the spare connector loca- (If the writer had a dollar for every time he tions on the back panel, provision has forgot to put tubing on a wire—or slip on

Issue 6, July 2015 Model 212 User Guide Page 30 Studio Technologies, Inc. a connector shell—before making a solder P7: AES3id Output, pin 1 not used, pin 2 connection…) signal, pin 3 shield. The Model 212’s enclosure must be disassembled prior to installing connectors Additional functions can be accessed in the spare locations. Four hex-head using these 3-position headers: machine screws, two on the bottom front P6: Auxiliary Relay Contact B, pin 1 of the enclosure and two on the back normally closed, pin 2 common, pin 3 panel, must be removed. A 5/64-inch hex normally open. driver is required. The cover can then be carefully separated from the chassis, P8: AES3 Output, pin 1 common, pin 2 remaining attached by means of a flexible high, pin 3 low. cable assembly. This “flex-cable” assem- P9: AES3 Input, pin 1 common, pin 2 bly links the main printed circuit board high, pin 3 low. assembly with the board assembly that contains the pushbuttons and LED indi- P11: Auxiliary Relay Contact A, pin 1 cators. Ensure that the flex cable is not normally closed, pin 2 common, pin 3 damaged while the Model 212 is being normally open. customized. For easier access, the push- P12: Auxiliary Input 2, pin 1 common, button/LED board assembly can also be pin 2 unbalanced analog audio, –10 dBu easily removed. nominal, pin 3 not used. The 3-position headers on the Model P13: Analog Main Output, pin 1 common, 212’s main circuit board assembly are pin 2 unbalanced analog audio @ –2 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 1, 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 not used, pin 2 signal, pin 3 shield. P15: Remote Data Interface, pin 1 common, pin 2 data +, pin 3 data – P2: Bidirectional Digital Interface, pin 1 not used, pin 2 signal, pin 3 shield. P16: DC Output 1, pin 1 common, pin 2 +12 volts, pin 3 –12 volts P3: External 24 Volt DC Input, pin 1 common, pin 2 +24 volts, pin 3 not P17: Remote Switch Connections, pin 1 used. Note: header P10 is used by the common, pin 2 main output control, pin 3 back-panel 24 Vdc jack assembly and talkback output control is electrically in parallel with P3. P20: DC Output 2, pin 1 common, pin 2 P4: Headphone Output, pin 1 common, +12 volts, pin 3 –12 volts pin 2 left (tip), pin 3 right (ring). P23: Analog Talkback Output, pin 1 P5: Microphone Input, pin 1 shield, pin 2 common, pin 2 unbalanced analog audio high, pin 3 low. Note: follows back-panel @ –2 dBu nominal, pin 3 not used. 3-pin female XLR pin assignment.

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 31 Pushbutton Backlighting pushbutton. Trim the LED leads to 0.25 inches in length and insert into the sock- For special applications, provision has ets with the cathode end located nearest been made to allow LED illumination the front of the Model 212. Power up the (“backlighting”) of the two pushbutton Model 212 and observe if the LEDs light. switches. This may prove useful for ap- They are polarity sensitive and if either plications where adequate room lighting is or both do not, remove the offending not available. It can also serve in custom LED(s), rotate them 180 degrees, and Model 212 configurations. It’s important to then re-insert. note that the button lighting is not intended to serve tally applications. It is strictly Remote Control Input intended to provide a moderate amount of illumination of the button’s clear lens and Connections associated labeling. Provision has been made on the Model From the factory, LED lamps are not 212’s printed circuit board assembly to installed in the pushbutton housings. The allow external switches or contact closures socket in each housing was designed for to control the main output and talkback inserting a pluggable T-1 bi-pin incandes- output functions. A 3-position header, la- cent type but we find that the more mod- beled P17, provides access to the circuitry ern leaded T1 LEDs work very well. The associated with the functions. Pin 1 of the Model 212’s 5 volt DC power supply is header is connected to the common point connected to the socket in each pushbut- of the Model 212’s circuitry. Pin 2 of the ton housings by way of 2.2 k (2200 ohm) header is connected to the circuitry asso- resistors. With this implementation, along ciated with main output pushbutton. Pin 3 with the recommended LED, only 1 milli- of the header is connected to the circuitry ampere per LED is consumed. associated with the talkback output pushbutton. The input circuitry is “active low,” It’s intended that high-efficiency white with a 10 k ohm resistor connected to LEDs be installed. They use very little DC +5 volts acting as a pull up. A combina- current and have essentially infinite life. tion of resistors and capacitors provides The recommended LED is the Kingbright ESD protection. A qualified technician can WP7104QWC/D which as of the time of use these inputs for special applications. this writing is available from sources such Contact the factory for additional details. as Digi-Key (www.digikey.com) and Mous- er Electronics (www. mouser.com). Digital Audio Outputs The mating socket in each pushbutton As has been previously discussed in this assembly is accessed by removing the user guide, the Model 212 is capable of button’s lens caps, graphic label, and supporting three digital audio outputs. back frosted lens. Once this is done in- Directly accessible on the back panel are stalling the LED should be very simple, the BNC connectors for the AES3id output requiring only lead trimming and careful and the bidirectional interface. Accessible insertion. Begin by removing the top clear internally for installer-selected applications lens, label, and frosted under-lens in each is the AES3 output. It’s important to men- tion that these three outputs are always

Issue 6, July 2015 Model 212 User Guide Page 32 Studio Technologies, Inc. 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. Remote Data Interface For future applications the Model 212’s main circuit board provides a bi-directional data interface connection. It complies with the RS-485 standard and operates at a data rate of 115.2 kbps. It is expected that the data interface will link the Model 212’s microcontroller integrated circuit with a remote switch/status display panel. Contact Studio Technologies to ﬁnd out the implementation status of this function.

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 33 Microphone Input/Preamplifier: Specifications Type: electronically balanced General Audio: Input Impedance: 2 k ohms, nominal Frequency Response: < –0.2 dB at 20 Hz, –0.6 dB CMRR: 75 dB at 60 Hz at 20 kHz, mic in/main channel out Gain Range: 10 to 50 dB, nominal, adjustable in Distortion (THD+N): 0.012%, measured at 1 kHz, 10 dB steps; 0 dB (no gain) also available mic in/main channel out Compatibility: dynamic or phantom-powered mics S/N Ratio: 77 dB, referenced to –46 dBu mic in/ Phantom Power: 48 Vdc, nominal, meets IEC –14 dBFS out 61938 P48 standard Connectors: Compressor: Mic In: 3-pin female XLR Threshold: –14 dBFS or –4 dBFS, switch selectable AES3id Out, AES3id In, Bidirectional Interface: Attack/Release Time: 2 mSec/100 mSec, nominal 75 ohm BNC Slope: 5:1, nominal Headphone Out: ¼-inch 3-conductor phone jack Status LED: compressor active 24 Vdc Power In: coaxial power jack, 2.1 x 5.5 mm, Headphone Output: 1, stereo locking bushing, compatible with Switchcraft S760K Compatibility: intended for connection to mono plug, center pin positive or stereo headphones or headsets with nominal Spare Connector Locations: 2 impedance of 100 ohms or greater Allows one or two Neutrik NC*D-L-1 connectors to Type: voltage driver be installed (*=3F, 3M, 5F, 5M, 6F, 6FS, etc.). Also Maximum Output Voltage: 12 Vpp, 150 ohm load compatible with Neutrik EtherCon. Auxiliary Relay: Digital Inputs/Outputs: Function: software configurable A/D, D/A Converters: 24 bit, 100 dB dynamic range Contacts: 2, form C (Common, Normally Closed, Normally Open) Sampling Rate: internal clock source 48 kHz, external clock source 32 to 96 kHz Rating: 1 A, 30 W (resistive) requires user-implemented connector AES3id In: unbalanced, transformer-coupled Access: Impedance: 75 ohms scheme Minimum Input Carrier Amplitude: 320 mVpp Power Source: 24 Vdc nominal, 150 mA max @ (SPDIF compatible) 24 Vdc; acceptable range 20-30 Vdc. Each unit AES3id Out: unbalanced, transformer-coupled shipped with a universal input/24 Vdc output power Impedance: 75 ohms supply. Output Carrier Amplitude (Loaded): 1 Vpp Analog Line-Inputs: 2, unbalanced, nominal level Bidirectional: unbalanced transformer-coupled –10 dBu. Optional cards can be installed to provide Impedance: 75 ohms support of balanced line-level analog audio sources Output Carrier Amplitude (Loaded): 1.75 Vpp with a nominal level of +4 dBu. Minimum Input Carrier Amplitude: 320 mVpp Analog Line-Outputs: 2, unbalanced, nominal level AES3 In: balanced, transformer-coupled (via –2 dBu. Optional cards can be installed to provide optional connector) balanced analog main and talkback outputs. Impedance: 110 ohms Dimensions (Overall): Minimum Input Carrier Amplitude: 200 mVpp 5.6 inches wide (14.2 cm) AES3 Out: balanced, transformer-coupled (via 3.3 inches high (8.4 cm) optional connector) 8.5 inches deep (22.4 cm) Impedance: 110 ohms Weight: 3.2 pounds (1.45 kg) Output Carrier Amplitude (Loaded): 3.5 Vpp Specifications and information contained in this User Guide subject to change without notice.

Issue 6, July 2015 Model 212 User Guide Page 34 Studio Technologies, Inc. Appendix A Attached to the bottom of the unit is a security plate with text that provides a summary of the conﬁgurable parameters and related information.

Model 212 User Guide Issue 6, July 2015 Studio Technologies, Inc. Page 35