PRIMARY SPECIFICATIONS
Frequency Response: 50 Hz - 20 kHz +1, -2 dB

Total Harmonic Distortion: < 0.20%, +4 dBm at main output, 50 Hz to 20 kHz (channel controls at 12 o'clock, master nominal)

Noise: (150 ohm source,
20 Hz - 20 kHz BW)
Equivalent Input Noise: -124 dBm
Output Noise: (channel controls full counter
clockwise):
Master full counterclockwise: -86 dBm Master nominal: -85 dBm
Output Noise: (channel controls at 12o'clock) Master nominal: -82 dBm

High-Pass Filter: 200 Hz, 6 dB/octave

Maximum Input Level: •
Channel Input (Mic): -30 dBu
Channel Input (Line): +23 dBu
Premix Input: +23 dBu
Mix Input: +23 dBu

KEY FEATURES
• Two Modes of Operation.
• Easy Setup with One Control.
• User Expandable with 1681 A
Input Modules.
• NOM=1 Function Automatically Adjusts from 0 dB to 20 log NOM dB.

The ALTEC LANSING ® 1684A Automatic Microphone Mixer is a rack-mountable, four-channel mixer that is designed for commercial sound reinforcement. It can be expanded up to eight channels by adding individual 1681A input modules. Each input channel exhibits balanced mic or line input with 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 I FD. The status LED not only displays the status of the input channel, but also gives a relative indication of the channel's gain. The master section features a remote volume control, priority/ mute system, and series/parallel link capabilities. By utilizing the linking, multiple units may be combined in either series or parallel configurations to establish conference systems of any size. For the series-combined configuration, one mixer in the system operates as the master, and the remaining mixers as extensions of the master. For the parallelcombined configuration, any mixer in the system may operate as the master. The maximum recommended number of automatically mixed channels for each series-combined or parallel-combined system is forty. The 1684A link system topology is similar to earlier models for compatibility with existing ALTEC LANSING sound installations.
The 1684A maintains the patented Dugan speech system, with an additional "live" mode of operation. In the "live" mode, an individual channel does not attenuate during speech pauses like most other automatic mixers. The "live" mode