The LM1894 is a stereo noise reduction circuit for use with audio playback systems. The DNR system is non-complementary and compatible with virtually all prerecorded tapes and FM broadcasts. It achieves 10 dB of noise reduction through psychoacoustic masking and an adaptive bandwidth scheme. It features low-cost external components and a wide supply range.
The LM1894 is a stereo dynamic noise reduction (DNR) circuit designed for audio playback systems. It operates with a wide supply range, low‑cost external components, and provides up to 10 dB of CCIR/ARM‑weighted noise reduction without requiring encoded source material.
The document includes absolute maximum ratings, detailed electrical characteristics, typical performance curves, external component recommendations, circuit operation explanations, and application hints such as placement before tone and volume controls and methods to adjust bandwidth and attack/decay times.
| Supply Voltage Range | 4.5 V to 18 V |
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The device operates with a supply voltage from 4.5 V up to 18 V.
Bandwidth can be changed by altering the values of capacitors C3 and C12 or by adjusting the size of C10, which sets attack and decay times.
The DNR system should be placed before tone and volume controls.