This invention relates to an audio mixing circuit for use in audio mixing consoles (audio mixers) or the like.
FIG. 1 shows a block diagram of one exemplary arrangement of audio mixing consoles using an audio mixing circuit according to the present invention. In operation, an audio signal applied to the input terminal 1 is passed (transmitted), through the head amplifier 2, the equalizer 3, and the fader 4, in this sequence. The output signal of the fader 4 is transmitted to the distance filter 5 for adjusting a sense of distance of a sound represented by the audio signal. In the distance filter 5, an audio signal level of the audio signal in an entire audio-frequency band and an audio signal level of a high-audio-frequency component extracted from the audio signal are attenuated or increased, in a correlated manner.
The output signal of the distance filter 5, of which the signal level of the audio signal in an entire audio-frequency band and the signal level of a high-audio-frequency component extracted therefrom have been attenuated or increased in a correlated manner, is then transmitted through the pan circuit 6 to the BUS 7.The output signal of the fader 4 is also transmitted through a variable attenuator 4a to the AUX 8. The output signal transmitted through the AUX 8 is fed to the external reverb circuit 9 in which a timber signal is generated and output. The output signals from the reverb circuit 9, transmitted from two output terminals thereof, are input through the input terminals 10, 11 to two separate audio mixing circuits as indicated by broken-line boxes, respectively, and the output signals of these audio mixing circuits are added to the original audio signal in the BUS 7. FIG. 2 illustrates a variation of the arrangement of the distance filter 5 for use with the audio mixing circuit according to the present invention, in which a variable resistor and a low-pass filter comprised of a capacitor-resistor (CR) device are provided. An operation of this embodiment of the distance filter 5 will now be described with reference to FIG. 2.
First, at both ends (of which one is grounded) of the variable resistor R1 is impressed an output audio signal of the fader 4, and an audio signal that has been voltage-divided in an arbitrary (or predetermined) proportion between a sliding contact of the
variable resistor R1 and the ground is obtained. The thus-obtained audio signal is fed to the low-pass filter comprised of the resistor R2 and the variable capacitor C1, and only a low-frequency audio component signal is extracted from an entire audio-frequency band and output through both ends (of which one is grounded) of the variable capacitor C1 to the pan circuit 6. The proportion of voltages divided in the variable resistor R1 and a capacity of the variable capacitor C1 (which is an element for determining the cutoff frequency of the low-pass filter) are adjusted in a correlated manner so that if the attenuation of the input audio signal by the variable resistor R1 is raised, an audio signal level of a high-audio-frequency component is attenuated. According to the present invention, an adequate adjustment can be made to a sense of distance from a sound source so as to make the sound more natural. The only operation required is to manipulate an AUX (quantity of signals transmitted from the post-fader terminal) and a distance filter (i.e., to adjust two adjustment elements). To be more specific, the need for adjusting three adjustment elements, as arising in a conventional audio mixing circuit, i.e., to attenuate an audio signal level using a fader, to attenuate high-audio-frequency components of the audio signal using an equalizer, and to adjust the
quantity of signals transmitted through AUX from the post-fader terminal can advantageously be obviated. Therefore, the load of an operator of the audio mixer can considerably be reduced, and the sound quality of programs produced by means of the audio mixer can be improved enormously.
