The sound fader control circuit TEA6320 is an I2C-bus controlled stereo preamplifier for car radio hi-fi sound application . The source selector selects one of 4 stereo inputs or the mono input. The maximum input signal voltage is Vi(rms) = 2 V. The outputs of the source selector and the inputs of the following volume control parts are available at pins 8 and 10 for the left channel and pins 23 and 25 for the right channel.
The volume control function is split into two sections: volume I control block and volume II control block.
The control range of volume I is between +20 dB and -31 dB in steps of 1 dB. The volume II control range is between 0 dB and -55 dB in steps of 1 dB.
The bass and treble control functions can be switched off via I2C-bus. In this event the internal signal flow is disconnected. The connections B2L and B2R are outputs and TL and TR are inputs for inserting an external equalizer.
The balance and fader functions are performed using the same control blocks. This is realized by 4 independently controllable attenuators, one for each output. The control range of these attenuators is 55 dB in steps of 1 dB with an additional mute step.
As the two audio channels (left and right) are independent, two comparators are built-in to control independent mute switches.
To avoid a large delay of mute switching when very low frequencies are processed, the maximum delay time is limited to typically 100 ms by an integrated timing circuit and an external capacitor (Cm = 10 nF).
The mute function can also be controlled externally ,if the mute pin is switched to ground all outputs are muted immediately (hardware mute).
The power supply should include a VCC buffer capacitor, which provides a discharging time constant .
This sound fader electronic project circuit needs to be powered by a DC power supply circuit that will provide an output voltage between 7.5 volt and 9.5 volt , typically a 8.5 volt DC power supply circuit is required .
