Studio Technologies Studio Technologies M74 Central Controller

PA SKU # STU M74 MFR # M74
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  • Product Highlights
  • 5.1 Surround Monitoring System with Analog I/O and Talkback

StudioComm 74&75 Create a 5.1 Surround Monitoring System with Talkback


The StudioComm for Surround Model 74 Central Controller and Model 75 Control Console work together to provide 5.1 surround and stereo source monitoring capabilities, along with a full-featured headphone "talkback" cue system. The system is a perfect fit for contemporary facilities that need to perform a variety of audio tasks. These can include surround and stereo mixing and monitoring, live recording of voice, music, and sound effects, and on-air broadcast applications. The system's features were carefully selected to provide extensive capabilities while remaining simple to operate. Of overriding concern is maintaining the quality of the connected audio sources. This is accomplished using a combination of excellent circuit design and carefully selected components. The Model 74/Model 75 combination is ideal for adding surround monitoring capability to disk-based recording systems. It's also well suited for upgrading a post-production or broadcast facility to support multi-channel monitoring.


A complete StudioComm for Surround 74/75 system begins with the Model 75 Control Console, a compact user control surface that is intuitive and comfortable to use. It is designed to reside at the operator's location. The Model 75 connects to the Model 74 Central Controller using a single 9-pin cable. Occupying one rack space, the Model 74 provides all audio input and output circuitry, signal routing and control, and power supply functions. To complete the system up to four Model 35 Talent Amplifier modules can be added. These connect to the Model 74 using standard 3-pin XLR-type audio cables. Model 35 units are typically deployed in voice-over booths, studio areas, or other locations where voice or music talent needs access to a headphone cue feed. Each unit provides a stereo audio amplifier, user controls, and support for one or two pairs of headphones.

Model 74 Central Controller

The Model 74 Central Controller is a single 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 applications the first surround input, Surround A, will be connected to a multi-channel output on an audio console or digital audio workstation. The second surround input, Surround B, will be connected to a playback device, such as a multitrack tape recorder or disk storage system. For film or video post applications 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 variety of 2-channel direct and playback sources. For flexibility, the surround and stereo inputs 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 input signals.

The Model 74 provides two 6-channel monitor outputs. A powerful system feature is the ability to configure the monitor outputs to meet the exact needs of an installation. In a "straight-ahead" application the monitor outputs might be configured to support two independent surround (5.1) loudspeaker systems. Alternately, one surround and one stereo monitor system could be connected. However, other more unique configurations are also possible. These include supporting alternate surround monitor speaker systems or adding additional LFE or surround speakers. The monitor outputs are electronically balanced and designed for connection to audio power amplifiers or amplified loudspeakers. Protection circuitry provides power-up and power-down protection of the connected loudspeaker systems.

Audio input and output connections are made using four 25-pin D-subminiature connectors. The Model 74's audio path features low-noise, low-distortion analog switches for input source selection and laser-trimmed voltage-controlled-amplifier (VCA) integrated circuits for monitor level control. One 9-pin D-subminiature connector is used to connect the Model 74 to the Model 75 Control Console. A second 9-pin "D-sub" connector is used to interface remote control signals with the Model 74. The Model 74's talent amplifier output uses a 3-pin male XLR-type connector. An infrared receiver module can connect to the Model 74 using a 3.5 mm jack.

An advanced 8-bit microcontroller provides the logic "horsepower" for the Model 74. AC mains power is connected directly to the Model 74, which is factory selected for 100, 120, or 220/240 V operation. The internal power supply utilizes two toroidal mains transformers for quiet audio operation.
  • Model 74 Central Controller
  • General Audio:
  • Frequency Response: 20 Hz-20 kHz ±0.1 dB (down 0.5 dB @ 60 kHz), monitor outputs
  • Distortion (THD+N): 0.04%, measured at 1 kHz, +4 dBu, monitor outputs
  • S/N Ratio: 87 dB, ref +4 dBu out, 20 Hz-20 kHz, monitor outputs
  • Crosstalk: 78 dB, typical, ref +4 dBu in, 20 Hz-20 kHz, monitor outputs
  • Audio Inputs: 16, organized as two 6-channel "5.1" inputs and two 2-channel "stereo" inputs
  • Type: electronically balanced, compatible with balanced or unbalanced sources
  • Impedance: 24 k ohms
  • Nominal Level: -12 dBV to +6 dBu, adjustable
  • Level Calibration: 15-turn trim potentiometers
  • Monitor Outputs: 2, 6-channel
  • Type: electronically balanced, compatible with balanced or unbalanced loads
  • Maximum Level: +27 dBu into 10 k ohms, +26 dBu into 600 ohms
  • Talent Amplifier Output:
  • Compatibility: provides power and audio signals for up to four Model 35 Talent Amplifiers
  • Type: DC power with two channels of unbalanced audio
  • Connections: common on pin 1, DC (+27 V nominal, 200 mA maximum) modulated with channel 1 audio (-10 dBu nominal) on pin 2, and channel 2 audio (-10 dBu nominal) on pin 3
  • Line-Level Cue Output: 1, stereo
  • Nominal Level: +4 dBu, nominal
  • Type: electronically balanced, capacitor-coupled, intended to drive balanced or unbalanced loads of 600 ohms or greater
  • Source Impedance: 100 ohms, nominal
  • Maximum Level: +20 dBu into 10 k ohms
  • Line-Level Talkback Input:
  • Level: +4 dBu, nominal
  • Type: electronically balanced
  • Impedance: 24 k ohms, nominal
  • Infrared Receiver Input:
  • Type: intended for use with industry-standard receiver module; data rate 650 baud
  • Remote Control Inputs: 4
  • Type: +5 Vdc logic, activates on closure to system common
  • Functions: mute, dim, talkback, input select
  • Downmix:
  • Functions: 5.1 to stereo, stereo to mono (mono-to-left-and-right, mono-to-center)
  • 5.1 to Stereo: LS @ -3 dB summed with L; RS @ -3 dB summed with R, C @ -6 dB summed with L and R; LS, RS, and LFE monitor outputs mute
  • Stereo to Mono (Mono-to-Left-and-Right): L summed with R to L and R or L summed with R to C; attenuation independently configurable; C, LS, RS, and LFE monitor outputs mute
  • Stereo to Mono (Mono-to-Center): L summed with R to C; attenuation independently configurable; L, R, LS, RS, and LFE monitor outputs mute
  • Stereo to Mono (Mono-to-Center) Bandpass Filter
  • Response: -3 dB @ 100 Hz and 5 kHz, nominal, 12 dB/octave
  • Connectors:
  • Audio: 4, 25-pin D-subminiature female
  • Talent Amplifier Output: 3-pin male XLR-type
  • To/From Model 75: 9-pin D-subminiature female
  • Remote Control Inputs: 9-pin D-subminiature female
  • Infrared Receiver Input: 3.5 mm 3-conductor jack
  • AC Mains: 3-blade, IEC 320 C14-compatible (mates with IEC 320 C13)
  • AC Mains Requirement: 100, 120, or 220/240 V, ±10%, factory configured, 50/60 Hz, 26 watts maximum
  • Dimensions (Overall):
  • 19.0 inches wide (48.3 cm)
  • 1.72 inches high (4.4 cm)
  • 9.58 inches deep (24.3 cm)
  • Mounting: one space (1U) in a standard 19-inch rack
  • Weight: 9.5 pounds (4.3 kg)
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