# My Android tablet Stereo Project



## chris45389 (Feb 26, 2014)

hi, I'm about to start a project soon turning an android tablet into a stereo head unit. 
One of the things I was not sure about is whether an idea I had would work.
to get audio to speakers and sub I was going to get a 3.5mm - RCA cable converter, then simply using a couple of double adaptors, connect them to all the channels in the amp for the sub. I know the fader/balancer options won't work but i don't really care about that.
I'm wanting to know whether this would work or not.

The plan is to take the accessories power to charge the tablet, have the audio coming out using the 3.5 jack to the two amps.
would this work?

thanks.
Chris.


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## WinWiz (Sep 25, 2013)

Yes it should work, but you will need a lowpass xover for the sub and a highpass xover for your speakers. Do your amps have high- and low-pass ?

Please note that analog audio from android tablets is rather low quality


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## chris45389 (Feb 26, 2014)

WinWiz said:


> Yes it should work, but you will need a lowpass xover for the sub and a highpass xover for your speakers. Do your amps have high- and low-pass ?
> 
> Please note that analog audio from android tablets is rather low quality


I haven't bought anything for it yet. just wanted to be sure it would work before starting. and yeah, getting the right amps won't be a problem. 

I was looking at some other people's way of doing this. and instead of using the aux jack. they used a parrot bluetooth and sent all the audio through this way. I can't imagine that giving better quality audio.

Any ideas for getting better quality then?


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## WinWiz (Sep 25, 2013)

Bluetooth compress the sound like mp3 so thats also low quality.
To get high SQ you need a tablet with a high quality dac (I'm not aware if any exist) or some digital audio output. Most people into SQ use the micro usb to get digital sound, but tablets like my nexus7 need a custom rom to support this. I think some tablets support digital out through a docking connector? But you will also need an external dac or an amp with digital input.
Tablets a cool and very convenient but requires so work if you want really great sound :surprised:
Its all been done before try using the search.

I recommend anyone interested in smartphone/tablet dac quality read this: http://www.anandtech.com/show/7567/smartphone-audio-quality-testing


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## 00goobs (Nov 14, 2010)

My android phone does usb SPDIF out when it is connected to a USB DAC. If your android device supports it, there is a big jump in quality going all digital. I've been playing with the miniDSP and there are devices from them that may allow you to go the all digital route affordably. You catually may want to use a windows tablet and play media and control the DSP from the same source.

The ipad does indirectly support digital output SPDIF through a camera connection kit. If you have an ipad, it is documented on how to get digital out to a DSP.

If you just want to have some fun with the tablet, you could use an affordable line driver to be sure you're getting enough signal to feed the amps. I would try to incorporate a volume control between the tablet and the amps?line driver. My ipad and windows tablet like to change volume settings randomly...


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## Dignan1443 (Apr 2, 2008)

This is an external DAC that I used in my tablet install: Amazon.com : Behringer UCA202 Audio Interface : Computer Audio Interfaces : Musical Instruments

If you have a tablet that supports audio out through USB, you can use this to then send the audio signal to your amp.


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## chris45389 (Feb 26, 2014)

Thanks. I'm wondering if I'm even going to need an amp now, I have a 04 Avalon which apparently has a factory amp. I just pulled it out and had a look and attached to the stereo is a device with the model ta277100 1290. I'm assuming this is the factory amp, I figure I could just connect straight through the original harness since it then goes through the amp then to speakers and sub just using the factory wiring. And that external dac you linked to. Is that as simple as connecting left and right RCA cables to the input and output? I couldn't see clearly what type of connections they are. If that's the case I can run audio through this then through the factory harness. 
I could be wrong about any of this Btw. Please let me know if I am.


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## WinWiz (Sep 25, 2013)

DAC = (D)igital to (A)nalog (C)onverter. 
All your music on tablet or CD is stored in digital format. But normal passive speakers needs analog input to drive them, that's why we need a DAC. 
Most external dac have normal (analog) rca output, but the input is digital like usb or spdif.
On Ebay you can find a lot of cheap china made external dacs, but do not in any way trust the manufacture specs. 
I don't know about the amp in your car, wiring a dac could be easy or very difficult, so you will have to do some research or talk to someone who knows the audio system in your car.
If you don't mind losing a little SQ and your car has aux input, finding a convenient source with decent analog output would be an easy route....


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## steveholt (Feb 25, 2014)

love this section, google search results in a lot of inconsistent information


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## chris45389 (Feb 26, 2014)

So I've hooked it all up. Sound works Fine I've encountered one problem though. The USB port doesn't charge the Samsung galaxy tab 3 tablet I've used. 
I've searched this problem and apparently they can only be charged By an Ac wall charger by USB. Does anyone think they can offer a solution. Also the USB is connected in parallel to the switched wire. With a device that drops it to 5V 2A (I'm about 60% sure that's the output)

After that the last step is just mounting it in the front panel

Ps. The amp I used was an alpine ktp - 445U


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## bigfastmike (Jul 16, 2012)

If it is like my Samsung phone you can get a micro USB cable that has an extra cable off to plug into charger. 

Sent from my SCH-I605 using Tapatalk 2


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## chris45389 (Feb 26, 2014)

so its all in and working. the solution i found was an iStyle Power Pill. boosts the amps to 2A to give enough power to charge.
now its just the little things i need to get fixed up. ie. when there's no sound playing through the tablet, i just get a crackly noise that is no doubt caused by the aux cable. I need a way to get rid of that.
any ideas?


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## chris45389 (Feb 26, 2014)

i, to control volume I have put in a potentiometer in the aux cable before the amp. Trouble is, when it is turned down, there is both static and an engine whine. 
How would I prevent this.
Thanks


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## WinWiz (Sep 25, 2013)

Im not an expert on this subject but I think you need a ground loop isolator to get rid of the engine whine.
What kind of pot did you use? I believe you may also need a hifi grade pot.
But a pot mounted near the source will make your rca voltage low and this is bad because it lowers the S/N ratio, so any induced noise will be worse.
Placing the pot at the end of the cable near the amp normally isn't practical so I would also advise you to use a high quality dual shielded RCA cables made with braided or twisted copper + foil.


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