Amplifiers – Hum or noise or distortion bucking introduced into signal...
Patent
1981-09-08
1984-04-03
Mullins, James B.
Amplifiers
Hum or noise or distortion bucking introduced into signal...
330284, H03F 126, H03G 318
Patent
active
044410832
ABSTRACT:
A noise reduction circuit for use in an audio signal recording/reproducing apparatus is comprised of a first signal path including a voltage-controlled amplifier for amplifying a signal supplied thereto with controllable gain and a differentiating circuit for differentiating at least that portion of the signal passing through the voltage-controlled amplifier within the audio range; a level detecting circuit for controlling the gain of the voltage-controlled amplifier in response to the level of the signal passing through the voltage-controlled amplifier; a feedback resistor connected as a negative feedback path with the first signal path for providing an upper limit to the gain imparted to the signal supplied to the noise reduction circuit; a subtraction circuit for subtracting the negatively fed back signals from the signal supplied to the noise reduction circuit to produce an input signal for the first signal path; a second resistor or a low-pass filter connected as a positive feedforward path between the input of the noise reduction circuit and the output of the first signal path for providing a lower limit to the gain imparted to the signal supplied to the noise reduction circuit; and an anti-limiting circuit connected in parallel with the feedback resistor for compensating the signal supplied to the noise reduction circuit when the level of the signal is abruptly increased.
REFERENCES:
patent: 4004253 (1977-01-01), Takasaki et al.
patent: 4080580 (1978-03-01), Takasaki et al.
Akagiri Kenzo
Katakura Masayuki
Ookouchi Motomi
Eslinger Lewis H.
Mullins James B.
Sinderbrand Alvin
Sony Corporation
Wan Gene
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