CloseHandy Surround Management!
The StudioComm 68A/69A Surround Monitoring rig is expressly designed to support 6-channel (5.1) monitoring. With the channels designated as left, center, right, left surround, right surround, and LFE, the channels can also be used in alternate arrangements. Using one 9-pin cable, the Model 69A connects to the Model 68A Central Controller. The Model 68A occupies just one rack space but allows connection of two multi-channel ins, two stereo inputs, plus separate 6-channel and stereo monitor outputs. With the StudioComm 68A/69A Surround Monitoring rig any audio console, disk-based recording system, or broadcast facility can have a complete multi-channel monitor rig.StudioComm 68A/69A Surround Monitoring rig at a Glance:
Model 68A Central Controller
Model 69A Control Console
Remote Control Capability
Limitations on Signal Routing
Model 68A Central Controller
The Model 68A Central Controller is one rack-space unit that contains analog, digital, and power supply electronics. Four analog sources can be connected: two surround (5.1) and two stereo. In many jobs the first surround in, Surround A, will be connected to a multi-channel out on an audio console or digital audio workstation. The second surround in, Surround B, will be connected to a playback device, such as a multitrack tape recorder or disk storage rig. For film or video post jobs Surround A would be considered the direct source, while Surround B would be considered the playback source.
The two stereo inputs, Stereo A and Stereo B, are provided for general-purpose use and can be connected to a bunch of 2-channel direct and playback sources. For flexibility, the surround and stereo ins are compatible with balanced or unbalanced signals having a nominal level range of -12 dBV to +6 dBu. Fifteen-turn trim potentiometers are used to precisely calibrate the in signals.
The Model 68A offers separate monitor outputs to support both surround (5.1) and stereo loudspeaker systems. The outputs are electronically balanced and designed for connection to audio power amps or amplified loudspeakers. Protection circuitry offers power-up and power-down protection.
Audio in and out connections are made using three 25-pin D-subminiature connectors. The Model 68A's audio path features analog switches for in source selection and laser-trimmed voltage-controlled-amplifiers (VCA) for monitor level control. One 9-pin D-subminiature connector is used to connect the Model 68A to the Model 69A Control Console. A second 9-pin "D-sub" connector is used to interface remote control signals with the Model 68A.
An 8-bit micro-controller sports the logic "horsepower" for the Model 68A. AC mains power is connected straight to the Model 68A, which is factory selected for 100, 120, or 220/240 V operation. The internal power supply utilizes a toroidal mains transformer for quiet audio operation.
Model 69A Control Console
The Model 69A Control Console is a small, self-contained unit designed to be located at the operator's position. It allows fingertip control of all monitoring parameters. Numerous LED indicators provide complete status details. A major strength of the Model 69A is its ability to configure, under software control, a number of operating parameters. All configuration parameters are stored in non-volatile memory.
The Model 69A rocks four buttons and associated LEDs for selection of the surround and stereo sources to be monitored. While in most cases only one in source will be monitored at a time, multiple ins can be selected for simultaneous monitoring. This allows two, three, or all four of the inputs to be combined ("summed"). While there is no independent control of the in levels, this feature can be useful for creating rough mixes from the source signals. It is also a fast, effective means of making a "seat-of-the-pants" check on the phase relationship between synchronized signals.
The surround and stereo monitor out levels can be controlled by way of a large, easy-to-use rotary control. The "curve" or "taper" of the level control can be configured to match an operator's preference. The choices available are true logarithmic and modified logarithmic. The level control auto mute-all function allow the monitor out channels to automatically mute whenever the rotary level control is in its fully counterclockwise (minimum) position. This is useful in jobs such as broadcast. By using the reference level function, the monitor output level can set to a pre-configured value. This is provided for audio-with-picture jobs that require a specific monitor level. The reference level is easily configured by taking an electronic "snapshot" of the position of the rotary level control.
For operator convenience, the dim function allows the monitor output level to be reduced by a fixed dB amount. The dim level is selected from four available levels. A mute all function allows all of the monitor output channels to be at once muted. The mute/solo section has individual output channel control. One pushbutton switch sets the operating mode for either mute or solo. In the mute mode, individual channels can be muted as required. In the solo mode, one channel can be monitored while the others are automatically muted. Depending on the configuration, multiple channels can be at once selected for "soloing." The flexibility of having both mute and solo available allows an operator to quickly select the most comfy and productive operating mode.
Two functions allow the format of the monitored sources to be checked for level or phase inconsistencies. The downmix function is used to make a stereo signal from a surround (5.1) source. The mono function allows a stereo signal to be added (summed) and monitored. The downmix and mono functions can be at once enabled, allowing a surround signal to be checked for mono compatibility. The mono operating mode can be selected from two choices: mono-to-left-and-right or mono-to-center. This allows support for both music and audio-with-picture jobs. A bandpass filter feature is associated with the mono function. It is included to assist an operator in determining compatibility with "real world" playback environments. A bandpass filter can be inserted into the path of the mono signal, allowing the response of a monaural loudspeaker associated with an inexpensive television or portable radio to be simulated.
The Model 69A Control Console connects to, and is powered by, the Model 68A Central Controller using a standard 9-pin D-subminiature cable. The Model 69A generates MIDI system-exclusive messages to control the Model 68A. Remote-control signals connected to the Model 68A Central Controller are routed to the Model 69A via pins in the 9-pin interconnecting cable.
Remote Control Capability
For flexibility, the StudioComm for Surround Rig is designed to easily combine with recording mixers, studio communications systems, and film motion-control electronics. Three remote-control in functions are provided: mute all, dim, and input source override. By providing access to the StudioComm's mute all and dim functions, talkback or slate activity from an audio console or other communications system can control the monitor output level. The input source override function is provided expressly for film post jobs, allowing automatic switching of the StudioComm's input source whenever the mode of a recording system changes between playback and record. This function, often referred to as PEC/direct switching, allows accurate monitoring during dialog replacement or other overdub sessions.
Limitations on Signal Routing
While the StudioComm for Surround system for multi-channel monitoring will do many wonderful things, it is not designed to selectively route input signals to the different output channels. The input-channel-to-output-channel relationship is maintained. A signal that arrives on the center channel of input 2 will, when selected, output only on the center channel of the monitor output. Any rerouting of the input signals must be done prior to their connection to the StudioComm for Surround system. This should not be a drawback in most facilities, but it's important to highlight this fact.
StudioComm 68A / 69A Surround Monitoring System Features:
- S/N Ratio: 92 dB, ref +4 dBu out
- Model 68A Central Controller
- Nominal Level: -12 dBV to +6 dBu, adjustable
- Power: provided by Model 68A Central Controller
- Impedance: 24 k ohms
- Response: -3 dB@100 Hz and 5 kHz, nominal, 12 dB/octave
- Model 69A Control Console
- Distortion (THD+N): 0.03%, measured at 1 kHz, +4 dBu, monitor outputs
- Bandpass Filter:
- Control: 2, 9-pin D-subminiature female
- AC Mains: 3-blade IEC-type
- Audio Inputs: 16, organized as two surround (5.1) and two stereo (2-channel) inputs
- Mounting: one space in a standard 19-inch rack
- Frequency Response: 20 Hz-20 kHz ±0.1 dB (down 0.5 dB @ 60 kHz), monitor outputs
- Remote Control Inputs: 3
- Max Level: +27 dBu into 10 k ohms, +26 dBu into 600 ohms
- Type: electronically balanced, compatible with balanced or unbalanced sources
- Application: supports Model 68A Central Controller
- Out Data: generates MIDI system-exclusive messages
- Connector: 1, 9-pin D-subminiature female
- Monitor Outputs: 2, one surround (5.1), one stereo (2-channel)
- Audio: 3, 25-pin D-subminiature female
- Type: electronically balanced, compatible with balanced or unbalanced loads
- Crosstalk: 78 dB, ref +4 dBu in
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