High quality Bluetooth audio in car

[sidlauskas]

Hi everyone,

Last week I got mine Dension Gateway BT Lite and I was surprised how bad the quality of the sound is when you stream the music via Bluetooth. I would expect this from 20 EUR but not 140 EUR device. The audio output is very low and you can always hear the hum noise coming from this device and it's not my sound system as there was no hum noises when I was listening to CD's from the CD changer. If you're interested I can post some high-res pictures of how does it look like from the inside.

But this post is not about this device. This device lead me to think about building my own Bluetooth audio module which would replace the CD changer and use it's audio input in the head unit. The idea is to get the best audio quality you can get from the Bluetooth as I'm currently not happy with the quality of the sound I get from Dension Gateway BT Lite.

Right now I'm thinking about connecting CSRA64215 to a DAC over I2S. Does anyone have tried this before? Any information related to this would be very helpful.

 

[sidlauskas]

I've decided to go with CSRA64215 and PCM5102 over I2S. I chose PCM5102 as it's simple to implement, won't require a lot of components and from what I found on diyaudio does it's job pretty well. For the prototype I ordered few boards from Aliexpress to check if it works and fit my needs.

 

[sidlauskas]

I need recommendations how to properly power CSRA64215 and PCM5102 and what voltage regulators to use for conversion from 12V to 3.3V. As these units will be used in the car, they will be powered from the car battery (12V from the headunit). Any thoughts or ideas?

 

[doctormord]

I'll look into this tomorrow.

 

[phase]

Much better choice to not use wireless unless absolutely necessary.
Arcam made some acceptable Bluetooth dacs, but I would rather use a dedicated player of some sort, wired.

I would like to have an alternative to my factory CD player, with a player that uses flash memory, inputting to the factory head unit.

Did you go directly into an amplifier from your first Bluetooth board?

 

[sidlauskas]

Yeah, I know that the best choice is to not use wireless, but I got a bit tired of searching the music in FLAC, then converting the files to WAV and finally playing them from USB (my car has an USB port in the glovebox). The sound quality when playing the records from USB is pretty decent, but the DAC it uses is very average. CD's sounds much better when listening to the same records. The headunit and infotainment system uses separate DAC's.

So why do I want to go wireless? The main reason is because it's easy and convenient way to play the music from the mobile phone using various music streaming platforms like Spotify. I can listen to my vinyls when I'm at home, in the car it's not that important.

I also thought about replacing my headunit with aftermarket double DIN, but this would require a lot of work and they're not a miracle either.

Phase: you mean did I got directly into amplifier from Gateway Lite BT?

 

[phase]

I didn’t know if you were going through the factory stereo or not...
I’ve used this before, just directly to an amplifier;
Arcam miniBlink Wireless Bluetooth(R) DAC at Crutchfield.com
Use the source to control the volume.

 

[sidlauskas]

I will go through the factory headunit to the amplifier. Here is the scheme:

CSRA64215 -> PCM5102 -> Headunit -> Amplifier

I can't go directly to amplifier because I would lose FM, USB port, CD and Hands-free functions. Going through the headunit will let me to have all these functions + to play music through Bluetooth.

By the way, nice device. I have not seen this device before.

 

[doctormord]

Using a TPS7A4700 might be a bit overkill but should work. You may need to seperate the supplies for both devices, depending on how much noise/hum/interference will be conducted from the CSR-implementation. Maybe an isolated 3.3V <-> 3.3V converter is needed.

 

[sidlauskas]

But what if I would separate supplies by using two TPS7A4700? Sorry for such questions, I'm completely new at this and still learning.

 

[sidlauskas]

Hi guys,

I have a couple of questions about power isolation as I want to isolate PCM5102 from CSRA64215 and Atmega168 using a couple of 3.3->3.3 converters. Does it make a sense isolating them in the way I did if at the end PCM5102 and CSRA64215 must have a common GND for a proper I2S connection? Atmega168 should also have a common ground with the CSRA64215 as I want to control it using Atmega. Here is the basic version of the current wiring diagram:

Any thoughts on this?

 

[randytsuch]

You could use a pi, turn it into a access point, and then you can connect your phone to it over wifi
I've played with this software, but didn't try the "car installation" which is what you would want.
pi audio receiver
Then you just need a pi, a dac hat for the pi, and clean power.

Randy