Analog Amplifier for Pine64

[mbt28]

Hi,

I would like to make an car amplifier extension board. Can anyone suggest me about the following topics:

- Volume adjustment (volume can be adjusted over I2C, what is the best way, adjusting volume of analog output of pine64 or tas524C)
- Audio input, there are four channels, pine64 has only 2 ch output. How can I do it?
- Fault, Mute, standby, clip_otw, is it necessary to use these pins with Pine?

http://www.ti.com/lit/ds/symlink/tas5424c-q1.pdf
(typical application circuit attached)

Thanks

[xalius]

I would probably program a fixed volume on the amplifier and regulate the rest from the audio codec side so you have normal software controls, but it also depends on the output/input drive levels of your amplifier circuit. As for four channel audio, do you need 4 different channels in your car? Usually it's only two with left front/back and right front/back so you just buffer the output from the Pine and feed that to two inputs? As for the control signals, that's up to how you want to use your amp and has basically nothing to do with the Pine... I would route them to some GPIO and set sane default logic levels... Maybe also add isolation for the audio path / power supply to avoid ground loops... Since you control some things via I2C you probably need to develop a 'fake' soundcard driver so you have a mixer device to control things....

[mbt28]

I have a quick question,

According to this schematic is the output differential or not? As far I see it is not, how can I make it differential?

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I found the evolution module schematics but doesnt seem well, the resolution of the pdf is very low.

http://www.ti.com/lit/ug/slou359/slou359.pdf

I would like to add si4703 fm module to the system but how can I convert the signal from single ended to differential?