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 Improve input audio signals to car audio system
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Posted - Nov 18 2016 :  01:36:45 AM  Show Profile  Visit yumi's Homepage  Reply with Quote
I am helping a friend to solve a low and not so clear sound to his car's audiosystem, when using aux-input in particular. He is getting great signals from CD or Radio, but when he feeds the audiosystem with analog in, it sounds "okay" but low. I have tried different quality cables and signal medias such as mp3, flac, WAV and streaming from youtube. Even with high quality cables and high resolution media files like flac, it did not sound as good as CD. I even tried with different phones, but still not satisfied.

And then I suddenly thought of this idea: "What if we transmit the data from the phone to a DAC (with a mini amp inside) and then further to the car's audiosystem." Would not that be awesome? I understand it is not easy to imagine how it will sound untill you try it. Therefore I drew couple of sketches on how to approach to a solution to the problem and also how to supply the DAC and the phone with power while the phone and the DAC exchanges data. All those three components interacting simultaneously. The third component here is a node (power source) from the car which is then transformed with a buck converter from 12V to 5V. Transformer can supply MAX 15 W power. That means it can supply max 3A current, from P = UI formula.

On second sketch I wonder if it would be necessary with a fuse or resistor next to the phone and the dac (in series with each of those to components, just like pointed on the sketch).

According to a article at digitalaudioreview, the DAC is supposed to drain 4-5mA. Let us say i want to allow it to get max 10mA. R = U/I = 5V / 10mA = 500#8486; and the phone to charge at max 1A. R = 5V / 1A = 5#8486;

My last question is would it be necessary with a resistor(http://www.kynix.com/Product/83.html) or a maybe a fuse or will those components drain as much as they need so I can expect it to go fine? What else would to do or not do to make this idea easier and realizable?

Edited by - yumi on Nov 18 2016 01:43:22 AM

Aaron Cake

6706 Posts

Posted - Nov 18 2016 :  10:23:37 AM  Show Profile  Visit Aaron Cake's Homepage  Send Aaron Cake an ICQ Message  Send Aaron Cake a Yahoo! Message  Reply with Quote
If I read that correctly, the problem he is having is that sound from the aux in sounds fine, but the level is very low?

Is this just a headphone mini jack style aux in? Or some other source?

Some systems have a gain feature for the aux in which is factory set to very low as it is designed to use a factory CD changer or similar system. Might need to turn up the gain in you can find it in the menus. It would help to supply make/model of the system.

Another choice is simply to use a preamp circuit to boost the level a bit. Stereo preamps are fairly easy to make. For example, this one:

Probably kits available too.
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Nobel Prize Winner

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Posted - Dec 07 2016 :  8:47:26 PM  Show Profile  Reply with Quote
What do you have to convert the 13V to 15V in the car to 5V? A transformer won't work and a resistor also won't work.
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