Electrical audio signal processing systems and devices – Including frequency control – Automatic tone control
Patent
1993-11-26
1994-10-25
Isen, Forester W.
Electrical audio signal processing systems and devices
Including frequency control
Automatic tone control
381106, H03G 900
Patent
active
053596650
ABSTRACT:
A device for enhancing the bass frequency components in an audio signal while avoiding overload problems associated with fixed levels of bass frequency enhancement. The device divides the input signal into two parts, the first of which passes through to the output of the device. The second part of the input signal is input into a low pass filter which passes only the bass components of the input signal and imparts a frequency dependent phase shift to the bass components. The bass components then pass through a variable gain amplifier which may or may not invert the polarity of the bass components and then are recombined with the first part of the audio signal. The gain of the variable gain amplifier is varied in accord with the level of the bass components. As a consequence the device provides greater enhancement of the bass frequencies when they are at lower levels and less enhancement when the bass frequencies are at higher levels, thereby reducing the likelihood of overloading any subsequent audio signal amplifiers. The enhancement is the result of a dynamically changing frequency response and increased duration of the bass frequencies.
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Don Lacaster, Active Filter Cookbook, 1979, pp. 46-57.
Aphex Systems Ltd.
Chen Tony D.
Isen Forester W.
Rozsa Thomas I.
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