ARCHITECT'S AND ENGINEER'S SPECIFICATIONS

The input preamplifier modules shall have phantom power capability, continuously variable high & low pass filters, adjustable gain, L + R stereo summing, and one shall have a 600 0 input transformer (1781AT). 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 (60 dB w/1 785A Input Transformer) continuously variable. Frequency response: 50 Hz to 20 kHz, ±1 dR. Source impedance:

150 0 to 10 kO with a balanced microphone or line level input, and 40 kO with a tape preamplifier. Equivalent input noise: <120 dB below rated output voltage with a 200 0 input termination. Total Harmonic Distortion (THD) @ 1 kHz: <0.01% (1781A) <0.025% (1781AT) at minimum gain. High pass filter corner frequency: 320 Hz, low pass filter corner frequency: 5 kHz. High and low pass filter slope: 6 dB/oct.

The input preamplifier module shall be the ALTEC LANSING Model 1781AortheALTEC LANSING Model 1781AT