The low-power audio amplifier employing IC LM386 (IC5) shown in Fig. One can use much higher-power audio amplifier along with the audio mixer circuit. The audio amplifier circuit shown in Fig. Since both the left- and right-channel input pins 15 and 4 have been shorted in this application, the IC acts as a mono volume/tone control circuit.) Audio Power Amplifier The outputs are available at pins 8 and 11 for right and left channel, respectively. Switch S2 is contour switch, which can be used to change the tonal response of the of the IC. Potmeters VR11, VR12, VR13 and VR14 are meant for adjustment of volume, balance, bass and treble, respectively. Bass emphasis can be increased by incorporating a double-pole, low-pass filter.Its output can drive most power amplifiers.Switchable contour (for quick changing of the tonal response).2: Circuit of audio mixer with bass, treble, volume and balance control A good heat-sink is necessary for longer life and better performance of the IC. Although it may work reasonably well with 9V DC supply, for better bass response, a 12V supply can be used. This IC serves as an efficient tone controller. All these functions can be controlled by DC voltages or by single linear potentiometers. It includes functions for bass and treble control, volume control with built-in contour (can be switched off) and balance.
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TDA1524A is designed as an active stereo-tone/volume control for car radios, TV receivers and mains-fed equipment. The amplified mixed signal output of IC 747 is applied to shorted input pins 15 and 4 of stereo tone controller IC TDA1524A (IC4). The overall gain of individual amplifiers can be adjusted with the help of potmeters VR9 and VR10, respectively.
The outputs of the two amplifiers taken from pins 12 and 10, respectively, are combined at the junction of resistors R9 and R10 before feeding to the next stage (tone controller) via capacitor C12 (10 ♟). Circuit Operationįor level adjustment, logarithmic variable resistors VR1 through VR4 and VR5 through VR8, respectively, are employed while feeding the output from respective microphones to the input of the two amplifiers inside IC 747.
Similarly, microphone outputs M5 through M8 are applied across the differential input terminals (pins 7 and 6) of the second amplifier inside op-amp IC 747 after their individual level adjustments. The microphone output signals M1 through M4, after their individual level adjustments, are mixed and applied across the differential input terminals (pins 1 and 2). In this application, +12V and –12V regulated DC supplies are used for operation of IC 747. The IC has short-circuit protection and wide common-mode and differential voltage ranges. The two internal amplifiers share a common bias network and power supply. Here, dual operational amplifier IC 747 (IC3) is used for mixing several inputs without any mutual interaction. 1: Block diagram of the audio mixer with bass, treble, volume and balance controls The power supply and audio power amplifier circuits are shown in Figs 3 and 4, respectively. 1 shows the block diagram of the audio mixing system along with the audio power amplifier, while the circuit of the audio mixer along with a tone controller is shown in Fig. For capturing the sound from various sources, the audio mixer employs up to eight microphones. Presented here is an eight-input audio mixer circuit with bass, treble, volume and balance controls, which you can use to balance sounds from all the sources until you have the desired mix. When recording direct to stereo master tape, it’s crucial to make sure that all the voices and instruments sound right before you hit the record button. When recording sound from several orchestral instruments being played by different musicians using a single microphone, the only way to adjust the sound balance is to change the position of the musicians relative to the microphone.
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