# Validation of Concept Arduino / Custom Headunit



## Luarana (Jan 2, 2018)

Hi All,

Bit of background. building a custom headunit for my 1988 BMW E30 motivated by the fact i have gauges where my radio should be. I have no desire to relocate the gauges as they are in a good location visibility wise. I have a useless clock and a whole lot of room behind the gauge cluster/old radio location to install a stealth unit. As such i decided to embark on building my own custom headunit. 

I'm in IT/Automation/Coding by trade and have a low level electrotech training in college. But only basic audio tech knowledge.

Equipment so far:

- Front end 2x16 Arduino controlled screen passing signals to a CSR8645 pairing to my phone via. BlueTooth4 Controls are via. 6 buttons. up, down, left, right, enter and exit. and controls are context sensitive via. the screen.
-Pioneer TS-WX120A Sub x 1, TS-A1376R x Speakers 4 and a GMD1004 AMP.

My issue:
I've got a proof of concept working with the CSR module and my Arduino. I'm at the point where i'm going beyond my knowledge and would like some validation. I would like to use a IC to control the settings. and Y Splitter my stereo into the IC and the subwoofer. My Current IC of choice is a TDA7313 which has built in fade/balance/volume/bass/treble control


The IC can effectively handle 4 speakers and i believe by Y-Splitting 2 signals into the sub. I would then output the signals to a RCA Connector going into my amp. 

Schematic goes something like this:

BT Module -> Y Splitter -> LME49721 *converts Differential to single output* -> TDA7313 -> Outputs to RCA Connector 

Otherside of Y Splitter goes into Subwoofer which accepts LN,LP,RP,LN as valid signals.

Other considerations: 
Power - Stepping down 12v to 6 - 10v for TDA7313/Arduino and 3.3v for LME49721 and CSR module.

Noise?? - Don't know much except strategically put caps and resistors. Seems to be enough enough projects using each component to piece together what i need maybe.


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## blaube (Sep 7, 2014)

Hello, 

I see it's been 10 months since you asked your question and no reply. I hope you figured it out. I cam across this looking for answers to my questions. I'm going to use a Lattepanda which has Arduino controller built in. I don't know coding, but do want to learn how to use the Arduino for other parts of the Jeep build. 

Like many people here, I have an extensive back ground in car audio and even home theater and dabbled in the PC arena. So I'll answer your questions as best as I understand them. 

You said - CSR8645 pairing to BlueTooth4 and TDA7313... 

I did a search on those items. I think that's great as long as it does not degrade the sound quality. Well, at least not below your personal standard of audio quality. It looks simple and easy to use. It's also your custom install and I'm all for that. 

My question would be the RCS line voltage from the IC components to the amps. You want to ensure you have plenty of voltage to overcome the noise floor and prevent noise. I looked up the specs on that amp and it says:

Maximum input level / impedance:
RCA ...................................... 1.0 V / 22 kW
Speaker .............................. 10.0 V / 22 kW

So, if you use the amp's RCA inputs, you need to ensure you have 1 volt of signal into it or 10 volts for the speaker level inputs. 

You didn't mention what amp you're using for the sub, but I don't recommend this amp unless you're going to keep the install as small and simple as possible. This amp has fixed gains:

Gain control:
RCA ...................................... Fixed 28 dB
Speaker .............................. Fixed 8 dB

This means you don't have any control over adjustments for clipping, sound quality, etc. 

You also mentioned using Y adapters. It can be done, but you could run into issues when you're trying to sum a signal for a subwoofer signal. You would need to solder 1000 ohm resister between the positive leads on the Y cable.

techtalk.parts-express. com/forum/tech-talk-forum/60443-stereo-to-mono-summing-circuit]Stereo to mono summing circuit? 

I suggest you not use the Y adapters and check out one of Audio Control's line drivers or other processors. audiocontrol. com

(I had to alter the links because I have not posted enough yet. Just copy and paste them into a search bar and you will find them.)

They will accept the signal from your IC and process it internally to give you the voltage you need for your amps and a summed subwoofer signal to send to your sub amp. This piece alone will do wonders for the entire system. 

I hope this helps. If you have already started the process, I'm interested in where you're at so far.

Brent


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## soFat! (Apr 25, 2011)

*Teensy *is the *best* for your audio arduino applications.
https://www.pjrc.com/teensy/td_libs_Audio.html

check this out:
"The Audio System Design Tool lets you easily draw a system to process 16 bit, 44.1 kHz streaming audio while your Arduino sketch also runs."
https://www.pjrc.com/teensy/gui/index.html


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## imickey503 (Dec 16, 2015)

Love these threads. Can't wait to show my proof of concept soon.


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