The automatic microphone mixer shall contain four input channels and be rack-mountable. It shall be constructed so that it can be expanded up to eight input channels by adding individual input modules. Each input channel shall have a balanced mic or line input with switchable phantom power for condenser microphones, variable input pre-amp gain control, line output for logging recorders, logic output, high pass filter, phantom power, automatic or manual operating modes, and a channel status LED. The status LED shall not only show channel status but also give relative indication of the channel's gain. The master section shall have a remote volume control, a priority/mute system and series/parallel link capabilities. The automatic microphone mixer's linking topology shall be similar to earlier models for compatibility with existing sound installations. The unit shall exhibit two modes of automatic operation. In the "live" mode, the system shall sound natural with the clarity of a manual mixer without microphone channel gating. The "mute" mode shall allow for individual microphone attenuation. The mixer shall adjustthe NOM=1 function from 0 dB to 20 log NOM dB automatically without manual setup.
The mixer shall meet the following performance criteria. Frequency response: 20 Hz to 20 kHz, +1, -2 dB. THD: < 0.20% at +4 dBm at main output, 20 Hz to 20 kHz, with channel controls at 12 o'clock and master at nominal. Equivalent input noise: -124 dBm with 150 ohm source, 20 Hz to 20 kHz BW. Output noise: - 84 dBm with channel and master controls full counterclockwise. Output noise: -83 dBm with channel controls full counterclockwise and master control at nominal, 20 Hz - 20 kHz BW. Output noise: -80 dBm with channel controls at 12 o'clock and master control at nominal, 20 Hz - 20 kHz BW. Maximum channel input (mic) level: -30 dBu. Maximum channel input (line) level: +23 dBu. Dimensions: 3.5 inches high, 19 inches wide, 12 inches deep behind the front panel. Weight: 141bs.
The automatic microphone mixer shall be the ALTEC LANSING' 1684A. The individual input module shall be the ALTEC LANSING' 1681A.