Dynamic Noise Reduction System DNR

General Description
The LM1894 is a stereo noise reduction circuit for use with
audio playback systems. The DNR system is noncomplementary,
meaning it does not require encoded source
material.
LM1894 datasheet

Servo Amplifier

NE544 datasheet

LM340/LM78XX Series
3-Terminal Positive Regulators
General Description
The LM140/LM340A/LM340/LM78XXC monolithic
3-terminal positive voltage regulators employ internal
current-limiting, thermal shutdown and safe-area compensation,
making them essentially indestructible.
LM7815 datasheet