Active Audio Processor AD-1304

• alternative name: Heath Company

The Heathkit AD-1304 is a vintage 1970s Active Audio Processor designed to improve audio quality through dynamic range expansion and noise reduction. Unlike systems like Dolby or dbx, it is a "non-encoded" processor, meaning it works on any audio source without requiring pre-recorded encoding.

Technical Operation:
Reviewers and technical documentation highlight several operational details:
Adjustability: One of its main advantages over similar consumer processors (like the Phillips DNR) is that its filtering and gain reduction are manually adjustable. 
Visual Indicators: The front panel includes a row of LED indicators and a level knob to help users monitor the processing and prevent "pumping and breathing" artifacts. 
Integration: It can be integrated into a system via a receiver's tape monitor loop or connected between a source and a preamplifier.

AD-1304 SPECIFICATIONS: Rated Input: 200 mV. Input Impedance: 100K ohms. gain: Expander off, 0 dB (unity) ±0.5 dB. Expander on, —3 dB to +4 dB. Frequency Response:
+0, —0.2 dB from 20 Hz to 20 kHz. High Filter: 7 kHz, 12 dB octave rolloff. Noise Reduction: 10 dB typical between 4 kHz and 15 kHz. Hum and Noise: —70 dB, 20 Z to 20 kHz.   Channel Separation: 50 dB at 1 kHz. Output Impedance: 500 ohms. Input Overload:
5 volts. Total Harmonic Distortion: 0.1% from 20 Hz to 20 kHz.                                         Power Requirement: 120/240 VAC, 50/60 Hz, 15 watts.

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