ARCHITECT'S AND ENGINEER'S SPECIFICATIONS

The input preamplifier modules shall have a 20 dB resistive pad, phantom power capability, a 300 Hz high pass filter, continuously variable gain, L + R stereo summing, and one shall have a 10 kst input bridging transformer (1780AT). In addition, the modules shall be fully compatible with the 1700-series mixer/preamplifier and mixer/power amplifier mainframes, and accept any one of the 1790-series input connectors.
The input preamplifier modules shall meet the following performance criteria. Gain: 50 dB, continuously variable. Frequency response: 50 Hz to 20kHz, ±1 dB. Source impedance: 1500 to 10 kn with a balanced microphone or line level input, and 40 k n with a tape preamplifier. Equivalent input noise: - 120 dB below rated output voltage with a 2000 input termination. Total Harmonic Distortion (THD): - 0.01%0 (1780A) at minimum gain, or ° 0.025°I° (1780AT). High pass filter corner frequency: 300 Hz. High pass filter slope: 12 dB/oct.
The input preamplifier module shall be the ALTEC LANSING Model 1780A or the ALTEC LANSING Model 1780AT.