Database Users

FLAC for car stereo.

is it possible to create an ipod emulator or a program that would interface with the car stereo and use the phone decoder and then send pcm wav format to the car stereo?
at the moment none (with exception of ipod) mp3 players use their own sound processing. and theres no flac support for car stereo. the car audio corporations are beeing big ******* and dont want to release the support for FLAC saying that the market is not big enough.( well because theres no support for it)
portable players and home audio already caught up to speed.
at the moment theres 2 options for car stereo
1 ipod that converts all audio to PCM(while applying apple sound processing and EQ) yes it is processed to sound "better".
ipod requires all your audio files to be in their format which is gay.
2 simple USB/mp3 player connection both act as a mass storage and the unit reads compressed data and uses onboard processing for supported formats(aac,mp3,wav,wma...) but still no flac.
to be more specific, pioneer's excuse was that flac needs more processing power which requires either programmable chip or more powerful ROM and it will probably cost them a dollar per unit to produce... yet they are spending time and money designing animated dolphins and other BS for their background...

fuzzysig said:
is it possible to create an ipod emulator or a program that would interface with the car stereo and use the phone decoder and then send pcm wav format to the car stereo?
at the moment none (with exception of ipod) mp3 players use their own sound processing. and theres no flac support for car stereo. the car audio corporations are beeing big ******* and dont want to release the support for FLAC saying that the market is not big enough.( well because theres no support for it)
portable players and home audio already caught up to speed.
at the moment theres 2 options for car stereo
1 ipod that converts all audio to PCM(while applying apple sound processing and EQ) yes it is processed to sound "better".
ipod requires all your audio files to be in their format which is gay.
2 simple USB/mp3 player connection both act as a mass storage and the unit reads compressed data and uses onboard processing for supported formats(aac,mp3,wav,wma...) but still no flac.
to be more specific, pioneer's excuse was that flac needs more processing power which requires either programmable chip or more powerful ROM and it will probably cost them a dollar per unit to produce... yet they are spending time and money designing animated dolphins and other BS for their background...
Click to expand...
Click to collapse
the recommended solution is to convert your flac files to mp3 in order to play them on your car stereos
i know a step by step guide on how to convert flac to mp3 on mac or windows at How to Convert FLAC to MP3 on Mac or Windows
hope it helps more or less

epic thread dig

FWIW: My Audiophile Adventures on Android
What's more important? : quantity or quality?
FLACs eat up sdcard space. that's just a fact. so why not stream it?
For those lucky enough to have UNLIMITED DATA PLANS
Oh, how sweet it is.
- Windows users, I HIGHLY recommend JRiver Media Center as your media server. Why? First, you can't go wrong with it as a base for HTPC anyway.. but because through it's companion app Gizmo (free in Play store), it is capable of using the same audiophile grade codecs to encode / decode your lossless files through URL streaming (HTML5 I believe) and preserve a respectable amount of quality. other solutions could include Plex, Plugplayer, etc.
Of course this works almost flawlessly on a decent WiFi connection, but my main purpose was 4G streaming on the road. I'd say as long as I have a solid 3G/low 4G, buffering for tracks is under 20 seconds. Full 4G is almost seamless (YMMV, I am streaming from a FiOS connection but I see no reason why broadband cable wouldn't suffice). The CONS: connectivity, passing between 3/4G, buffering large amounts of data seemlessly... it's not perfect yet but it definately beats paying for Spotify :good:
For the Less Fortunate! And Data Scrooges!
or you just don't wanna wait.
- Assuming an sd-card + internal doesn't satisfy, you will need to assess your device's USB host capacity. the ultimate goal in this case is to use USB storage to accommodate large collections. You will need a USB OTG cable (they are largely universal but check the reviews). Furthermore, most devices have a different condition for enabling OTG support.
For example: SGS3 is simply plug-n-play for thumb drives up to keyboards. I have a Droid Bionic which comes with several expensive docks, but can be OTG capable with an externally powered USB hub + OTG cable.​
ICS brings necessary usb storage drivers, all that's left is tuning up your operating system to produce the best possible output.
(i'll probably add as an addendum to this post in the near future if there's interest)
---
Signal Path Overview (mostly FYI)
---
if that all seems reasonable to you (music is of course a subjective experience!)- unless you have a high-end after market stereo, chances are your audio output at this point will sound terrific with a simple aux cable. People mistakenly believe their iPods/mobile devices have inferior DACs and that full digital pass through produces the highest quality. What these devices are lacking isn't conversion quality, it's amplification. Any audio buff, or avid listener for that matter, knows that source degradation occurs when software amplification / coloration is introduced PRIOR to gain stage(actually, at any point in the chain if you're an elitist ). it is for this reason that adjusting EQ on your car stereo will typically sound better than doing so on your phone. our aim is to output from the phone's aux jack the *cleanest source material possible*, even if the signal seems "quiet".
not surprisingly a well preserved MP3 at 320kbps can sound indistinguishable if not BETTER than a FLAC at ~800kbps played through Poweramp with bass knob turned up and various stock EQ settings on top of Beats Audio, 3D sound stage, DSP, etc etc. keep in mind that many of those audio effects are designed for earbud use. they attempt to compensate for weak headphone playback by augmenting the strongest frequencies (like bass and high-end treble) and adding virtual "space" to the sound with reverb. this is why beats earphones, when coupled with beats audio software, sound A LOT A HELL louder and "crisper" than average headphones.. the headphones and the software component are doing similar things, just on a hw vs. sw level. (not my cup of tea, but it's a brilliant use of simple acoustics to wow consumers, eh?)
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Mobile Audio Considerations
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car head-units and discreet amplifiers, on the other hand, don't need as much help... depending on hardware of course. i'll use my own arrangement (though somewhat unique due to Motorola hardware) as an example of how this could play out:
- Lossless source audio is outputted by capable app (in my case, Neutron Player)
- Droid Bionic sits in Motorola Vehicle dock which features a proprietary Y-cable that carries analog audio over USB + charges
- Because of the analog signal going out through USB, the phone bypasses software DSP / volume controls (the assumption being that you are connecting to a stereo with a stronger amp!). this is for all intents and purposes the cleanest signal that Android can output without more components in the chain. the intent is more than just clear, the design of the dock+cable disables the OS from adding DSP or software amplification. this is true of a handful of manufacterer docks.
- 3.5 mm aux cable connects the terminating end of the Y-cable to head-unit Aux in
- Head-unit outputs stereo RCA to a discreet amplifier in trunk
- Amplifier drives component speaker system​
Don't be afraid to turn the knob to say 30 when your CDs play at 20 (just make sure to turn it BACK down! ), but on most stock radios you don't want to crank past 70% of max volume. i like my music loud but more importantly *clear*... but i guess if you've gotten this far in a FLAC thread you're already convinced!
---
Links / Resources
---
CableJive-dockBoss-Smart-Adapter-iPhone
- this is a really nifty hw hack that basically allows any portable music device to hijack iPod docks/connections. it does *not* add digital audio playback, it is simply injecting an analog signal into a pre-existing dock or stereo system.
For Motorola Users: The Y-cable for Droid 3 and up devices (?) is hilariously difficult to obtain if you have already purchased a vehicle mount from Verizon or any non Moto OEM package. For whatever reason, they loathe selling the cable as a seperate item and will likely charge you ~$20 (though best grudging investment of my life). Details:
Bionic Car Mount Y-Cable Discussion (External)
And for the truly adventurous:
[DIY] "Car Dock" Cable - USB audio out + charging - UPDATED! (11-9-11)
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Potential Future Topics
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Basic Android Optimizations for Audio Quality
Network / Connectivity Tweaks for Streaming
(True!) Digital Audio Output : External USB Components Overview
Desktop / Mobile Software Recommendations / Reviews
FAQ?
this started as a harmless reply to OP but, we can't help ourselves sometimes, heh. if there's interest feel free to suggest something, I'm no expert but im sure i'll have 2 cents at the least! i'd love to see a serious A/V resource eventually come together for Android as devices are rapidly evolving and opening new possibilities.
---------- Post added at 10:06 AM ---------- Previous post was at 09:47 AM ----------
polobunny said:
epic thread dig
Click to expand...
Click to collapse
it was meant to be my friend.:good:

JVC released few NAV units with flac support finally
so no need for this anymore.
and thanks again for letting me know that i can convert flac to MP3 lol for the 10000000000000th time

Using as Car Head Unit??

Ok so Ive been looking in to building a Android tablet in to my car to use as a head unit.
Ive been looking around at different tablets and the A7 definitely looks the best for my budget.
Basically im running amps in my car so i need an audio signal from the unit.
I DONT want to simply run the 3.5mm headphone jack cable to the amps cause it will sound shocking.
I was just wondering if there are other ways of doing it.
I was looking in to something like sending the audio out the usb but i dont think they can do that.
But what interested me was using the HDMI audio out and using a DAC (digital audio converter i think) and converting the signal to analogue.
Does anyone know if this is possible at all or if there are better ways of doing it?
Ive been spending hours trying to find out a way of doing this!

There are converters available to go from HDMI to standard RCA outputs.

You could run the 3.5mm output through a preamp - the sound quality is pretty good, especially with good filtering, although a preamp with HDMI or SPDIF input would be better (you'll also need a HDMI-SPDIF adapter for the latter)...

Android 5.1 head unit >>> USB Audio (DAC) output

Hi, I installed a MTCD Android head unit with Android 5.1.1 in my car two weeks ago. (I could'nt start this thread in the MTCD section because I'm new here)
My car audio setup goes as follow: Android Head Unit >>> USB Cable >>> PCM2704 USB to SPDIF adapter >>> SPDIF coax cable >>> MiniDSP 6x8 >>> 3 Amps >>> Speakers + sub.
So far I've been able to get SPDIF sound output with Neutron (Direct USB mode), Onkyo HF Player, USB Audio Player Pro, HibyMusic Player.
Sound is amazing btw.
If I understand correctly, all these apps are working with the USB DAC because they use their own app's USB Driver.
Important to know: All song in 44khz are playing fine, songs in 48khz makes every app freeze. I got a way around this by setting Neutron to resample every song in 44khz, so all songs are working now.
Now, if I play a song in Google Play Music, Spotify, Kodi, etc no sound comes out ... same thing for my HU video app, phone calls etc.
Is there a way around this ? What modifications can be made so every sound outputs to the USB Audio ? IE. kernel update, system files modifications etc ??
Thanks for any input.

Nobody use a USB DAC with his head unit ?
I have found this thread: http://forum.xda-developers.com/showpost.php?p=66707293&postcount=47
But I dont think it applies to Android 5.1, sound management is different.

i dont use any DAC on this head unit. But I do have a Dragonfly USB DAC on my computer. the Dragonfly Red says it works with Android. Not sure if that is just marketing, or if it doesn't something specific.

CadillacMike said:
i dont use any DAC on this head unit. But I do have a Dragonfly USB DAC on my computer. the Dragonfly Red says it works with Android. Not sure if that is just marketing, or if it doesn't something specific.
Click to expand...
Click to collapse
Can you try it please ?

DanB0y said:
Can you try it please ?
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i dont know how I would even go about hooking it up? i could plug it into the USB port, but then what? use headphones?
all my speakers go through the wiring harness

CadillacMike said:
i dont know how I would even go about hooking it up? i could plug it into the USB port, but then what? use headphones?
all my speakers go through the wiring harness
Click to expand...
Click to collapse
you would need to be using pre-outs, using a 3.5mm to rca cable into an external amp.
---------- Post added at 09:03 AM ---------- Previous post was at 08:57 AM ----------
interesting that you've tried this. This forces you to completely by-pass the HUs sound processing.
I have the same DSP, but I'm using direct pre-outs. I like this idea though bc it gets around the low pre-out voltage, and allows you to ignore the poorly implemented sound processing in the HU.
Unfortunately, you probably need to modify the filesystem to get this to work, as your link shows. Why do you feel the need to use a DAC in addition to the DSP?

Hisma said:
you would need to be using pre-outs, using a 3.5mm to rca cable into an external amp.
Click to expand...
Click to collapse
my sub is tapped into my speaker wires, so I dont use the RCA preouts. So I probably can't try this.
However, I think my audio is pretty great with the Joying

CadillacMike said:
i dont know how I would even go about hooking it up? i could plug it into the USB port, but then what? use headphones?
all my speakers go through the wiring harness
Click to expand...
Click to collapse
Yes simply use headphones
We just need to know if audio is outputing from the DAC.
I would appreciate, thanks !

Hisma said:
Unfortunately, you probably need to modify the filesystem to get this to work, as your link shows. Why do you feel the need to use a DAC in addition to the DSP?
Click to expand...
Click to collapse
The DAC is a really clean source signal VS the head unit, I have a 2000$+ sound system in my car and sound quality is very important to me.
Also, DAC is digital signal VS analog RCA outputs on the head unit.

DanB0y said:
The DAC is a really clean source signal VS the head unit, I have a 2000$+ sound system in my car and sound quality is very important to me.
Also, DAC is digital signal VS analog RCA outputs on the head unit.
Click to expand...
Click to collapse
I agree. I feel like right now my HU is the "weak point" of my system. I am about the same as you, roughly $2000 in equipment (probably a little more).
focal KRX3 3-way active system w/ a cheap kicker sub + 3 amps. I have the C-DSP along w/ a line driver to manage the low pre-out voltage. Would love to take the line driver out of the signal chain if I could. All these components are taking up a lot of valuable space.
I hope you figure this out. I don't have a MTCD, I have a non-joying 4.4 HU. Would love to use the SPDIF inputs on the C-DSP as opposed to the ****ty pre-outs from the HU.

Hisma said:
I agree. I feel like right now my HU is the "weak point" of my system. I am about the same as you, roughly $2000 in equipment (probably a little more).
focal KRX3 3-way active system w/ a cheap kicker sub + 3 amps. I have the C-DSP along w/ a line driver to manage the low pre-out voltage. Would love to take the line driver out of the signal chain if I could. All these components are taking up a lot of valuable space.
I hope you figure this out. I don't have a MTCD, I have a non-joying 4.4 HU. Would love to use the SPDIF inputs on the C-DSP as opposed to the ****ty pre-outs from the HU.
Click to expand...
Click to collapse
Nice ! I have 3 way peerless (tweets + 3.5 mids + 7in woofer) 1 pioneer amp 4ch for tweets + mids and 1 pioneer amp 2ch for the woofers, another JBL amp in the trunk with a 15in Alpine Type-R. I have the C-DSP 6X8 MiniDSp as well

SPDIF to C-DSP SPDIF Input would give you 4V at the MiniDSP RCA outputs

DanB0y said:
SPDIF to C-DSP SPDIF Input would give you 4V at the MiniDSP RCA outputs
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Click to collapse
well you have convinced me to give this a shot. The USB DAC + 25 ft coax cable only set me back $35 on amazon. So even if this doesn't work I won't be mad.
The potential for 4V of CLEAN pre-out voltage is too enticing to pass up. The line driver works, but like I said it's another box that needs power/space/etc. The USB DAC also allows me to take the HU sound processor fully out of my signal chain.
I am unfortunately using android 4.4, so dont think I can help you much, but I will let you know if this works nonetheless.

Hisma said:
well you have convinced me to give this a shot. The USB DAC + 25 ft coax cable only set me back $35 on amazon. So even if this doesn't work I won't be mad.
The potential for 4V of CLEAN pre-out voltage is too enticing to pass up. The line driver works, but like I said it's another box that needs power/space/etc. The USB DAC also allows me to take the HU sound processor fully out of my signal chain.
I am unfortunately using android 4.4, so dont think I can help you much, but I will let you know if this works nonetheless.
Click to expand...
Click to collapse
If it dont work natively, I'm 99% sure it will work with the Neutron music player. Install it and then go to hardware settings and enable Direct USB Driver. :good:

DanB0y said:
If it dont work natively, I'm 99% sure it will work with the Neutron music player. Install it and then go to hardware settings and enable Direct USB Driver. :good:
Click to expand...
Click to collapse
well I tested this today and I am very pleased with the results. I really do notice a difference in SQ. It sounds "cleaner" and fuller.
Only major thing I notice is the overall volume seems really high over SPDIF. Only place I can adjust the volume now is with the DSP, but even then, I find I need to turn the gain down on the SPDIF inputs to get an acceptable volume. This is even with gain all the way down on my amps. This leads to a bit of clipping on the highs.
Did you make any adjustments in neutron player or the DSP to get an acceptable volume? Or do you get by with just adjusting the DSP master volume?
Now I just need to see if I can get all my sound to route through. I like to listen to streaming music too but I don't think I can go back to using analog pre-outs.

Hisma said:
well I tested this today and I am very pleased with the results. I really do notice a difference in SQ. It sounds "cleaner" and fuller.
Only major thing I notice is the overall volume seems really high over SPDIF. Only place I can adjust the volume now is with the DSP, but even then, I find I need to turn the gain down on the SPDIF inputs to get an acceptable volume. This is even with gain all the way down on my amps. This leads to a bit of clipping on the highs.
Did you make any adjustments in neutron player or the DSP to get an acceptable volume? Or do you get by with just adjusting the DSP master volume?
Now I just need to see if I can get all my sound to route through. I like to listen to streaming music too but I don't think I can go back to using analog pre-outs.
Click to expand...
Click to collapse
Great ! Now you're in the same boat as me lol
(Except for the clipping, I have no problem with that)
What is the model of your amps ? I have my gain to around 1/3 in the amps (They're up to 6.5V input sensitivity) and spdif input gain is at 0.
For your sound routing, you can sum the rca inputs and the spdif input together in the DSP And then you use your input levels to match the loudness. That way, you'll be able to listen excellent SQ music from Neutron and still hear BT phone calls, Youtube, navigation etc trough the analog inputs.

DanB0y said:
Great ! Now you're in the same boat as me lol
(Except for the clipping, I have no problem with that)
What is the model of your amps ? I have my gain to around 1/3 in the amps (They're up to 6.5V input sensitivity) and spdif input gain is at 0.
For your sound routing, you can sum the rca inputs and the spdif input together in the DSP And then you use your input levels to match the loudness. That way, you'll be able to listen excellent SQ music from Neutron and still hear BT phone calls, Youtube, navigation etc trough the analog inputs.
Click to expand...
Click to collapse
Yes! This is exactly what I have done. I spoke too soon also. The clipping was more a tuning issue than anything (changed cross-over on tweeters & lowered their output a bit). I was able to set the gain on SPDIF back to 0.
Man it sounds really good now. I haven't any real tuning yet outside of setting gains and cross-overs. I think once I tune the system it'll take it over the top.
I have a mosconi as100.4 on the tweeters and mids, and a alpine mrv-m500 on the sub. (i have one other amp I am replacing to power mid woofer, should arrive tomorrow). It's a total overkill system, but I find great deals on used gear on diymobileaudio classifieds so I keep upgrading lol.
So now I will use neutron for majority of listening, and by mixing channels together on the analogs I already had connected, I get acceptable SQ for phone calls and streaming music. I have no desire to mod my system files the way it was shown in that thread you linked. Looks too risky. I am okay with this new arrangement since 90+% of my listening is my personal music collection.
Really appreciate you making this thread. I always knew my system was capable of sounding better and this did the trick. I will let you know if I figure anything else out that could be useful.

Hisma said:
Yes! This is exactly what I have done. I spoke too soon also. The clipping was more a tuning issue than anything (changed cross-over on tweeters & lowered their output a bit). I was able to set the gain on SPDIF back to 0.
Man it sounds really good now. I haven't any real tuning yet outside of setting gains and cross-overs. I think once I tune the system it'll take it over the top.
I have a mosconi as100.4 on the tweeters and mids, and a alpine mrv-m500 on the sub. (i have one other amp I am replacing to power mid woofer, should arrive tomorrow). It's a total overkill system, but I find great deals on used gear on diymobileaudio classifieds so I keep upgrading lol.
So now I will use neutron for majority of listening, and by mixing channels together on the analogs I already had connected, I get acceptable SQ for phone calls and streaming music. I have no desire to mod my system files the way it was shown in that thread you linked. Looks too risky. I am okay with this new arrangement since 90+% of my listening is my personal music collection.
Really appreciate you making this thread. I always knew my system was capable of sounding better and this did the trick. I will let you know if I figure anything else out that could be useful.
Click to expand...
Click to collapse
Yeah I know what overkill sounds like haha
For frontstage 3way I got a 4ch Pioneer Premier PRS-X340 running 2x NE25-VTS04 Peerless tweets and 2x NE95W-04 3in Peerless mids, another Pioneer old scholl amp pushing 2x175w for 7in Wavecor woofers. In the trunk is a JBL GTO14001, 1500Wrms @2ohm pushing a 15In Alpine Type-R sub in 3.5cuft tuned @21hz
All my amps are very good condition used gear found on classifieds too, you can dig some real treasors for very little money sometimes !
I've been looking all around the web since last week for how to route every sounds of the HU to a USB DAC, translating and reading about 500 pages worth of XDA/Russian Android forums, spent last nights editing config files all around my HU System folder, I tried the how-to link I posted in OP for MTCB units, nothing to do.. I really think the Kernel must be enabled for USB Audio for it to work, my DAC shows up in USB devices info but not in the audio output devices.
Well, I'm still happy because my FLAC music collection plays incredibly well i dont car that much for FM Radio SQ, I only wish I'd be able to listen to Spotify or Kodi on the DAC.
Im r eally glad if I could be any help to you and will keep this thread updated if I find something !

navigation guidance voice goes through usb audio ?

DanB0y said:
Yeah I know what overkill sounds like haha
For frontstage 3way I got a 4ch Pioneer Premier PRS-X340 running 2x NE25-VTS04 Peerless tweets and 2x NE95W-04 3in Peerless mids, another Pioneer old scholl amp pushing 2x175w for 7in Wavecor woofers. In the trunk is a JBL GTO14001, 1500Wrms @2ohm pushing a 15In Alpine Type-R sub in 3.5cuft tuned @21hz
All my amps are very good condition used gear found on classifieds too, you can dig some real treasors for very little money sometimes !
I've been looking all around the web since last week for how to route every sounds of the HU to a USB DAC, translating and reading about 500 pages worth of XDA/Russian Android forums, spent last nights editing config files all around my HU System folder, I tried the how-to link I posted in OP for MTCB units, nothing to do.. I really think the Kernel must be enabled for USB Audio for it to work, my DAC shows up in USB devices info but not in the audio output devices.
Well, I'm still happy because my FLAC music collection plays incredibly well i dont car that much for FM Radio SQ, I only wish I'd be able to listen to Spotify or Kodi on the DAC.
Im r eally glad if I could be any help to you and will keep this thread updated if I find something !
Click to expand...
Click to collapse
Any update on this thread ?
I made some sort of experiance, on Joying HU , the 2GB Rockchip Sofia version (10.1" screen) :
Using info from https: // source.android.com/devices/audio/usb.html - i looked into the "audio_policy.conf" file on the Joying, and for sure , there was no reference to any USB audio interface.
I am no android expert .. but i edited this file , with the info gathered from the link above , and after a reboot - the HU did indeed send the audio to the USB port.
Audio from all the apps i tred , was routed to the USB interface (Radio , DAB player,Kodi etc..)
The bad thing (?) - there was no volume control , all audio is at max level.
An external volume control could possibly remedy this.. i will look into it
Frank

Connecting via USB to processor/DAC - Eonon GA8150 Android 7

Hi Guys
I have been searching and researching for hours but can't get this to work the way that I want, although I don't see any reason why it shouldn't work.
I recently purchased one of my dream cars, and promptly changed the headunit to a more modern unit, to allow me to have spotify, google maps, etc etc. I purchased the Eonon GA8150A for this purpose, and it sounds OK.
I was always planning to upgrade the sound, namely using a Helix DSP and amplifier, upgrading the speakers, etc etc.
Since the helix has an optical input, I figured I could maximise quality by running a digital signal to the unit - to this end I purchased a Behringer UCA202, as its a class compliant USB DAC which has optical out.
I connected via USB, and went into developer settings, and changed the "Select USB Configuration" to Audio. I plugged in some headphones for testing, and....nothing.
After some research, I downloaded the Onkyo player, and this worked! I was getting audio via my USB dac, through the headphones. But spotify, bluetooth, radio, nothing else worked.
Was wondering if what I am trying to achieve is possible?
The only other alternative it to sell the uni, and purchase an AVIN Avant 3 unit - this comes with high quality 4V pre outs but its a lot more expensive and i really dont want to do this. I could use the RCA outs on the Eonon to feed the processor, but as mentioned, these leads to many stages of A/D D/A conversion that will markedly reduce quality.
Thanks
Saad

Ok updates - it now works - the inbuilt audio player via USB, spotify, both work, however the radio doesn't send audio via the DAC, and nor does it send audio to the dac from my phone via bluetooth.
Not sure why this works now, maybe I had to turn off the car a while so the unit could properly reset?
The head unit volume control however doesn't work to adjust the volume of the audio coming from the dac.
Any way to get radio and bluetooth working via the dac?
Cheers

Digital Audio Out via USB

The amp in my car (BMW E39) has a S/PDIF coaxial input that will only work at a sampling rate of 44.1khz. At the moment, I have the RCA analog line-level outputs of my head unit (Dasaita Max6, Android 9) running directly into an ADC that I have mounted on the back of the head unit, and from there I just run a single coax cable to the back of the car that then plugs into the amp. This sounds great to my uneducated ears, however it bugs my OCD-ness that the head unit is converting from digital to analog, and then I am converting this straight back to digital again. It would be better if I could just run a digital signal al the way through.
So, as an experiement, I bought a cheap USB to S/PDIF sound card off ebay (PCM2704), which I hoped that I would be able to plug into one of the USB outputs on the head unit and instantly get digital audio. Only it didn't work. I tried a heap of things and I could not get the head unit to output audio via USB. I did a bit of sniffing around the file system, and found all of the audio-policy configuration files (all are XML) in the /vendor/etc directory. There is a USB Audio policy file there, however the main audio policy file makes no reference to it. The main file recognises a heap of audio outputs (bluetooth, headphones, speakers etc), but neglects USB.
This is as far as I have gotten so far. There is very little info available on this that I could find. I few people managed to get this sorted on Android 6, but all of the audio policy files changed between Android 6 and 9. My next step is to see if I can add USB to the main audio policy file and see if that works, but before I do that, I thought I would post here and see if anyone else had tried this before.
I'm aware of things like USB Audio Player Pro, which uses it's own proprietry drivers to send audio out via USB, but this is not really suitable to me as it won't work with other audio sources, like Youtube, youtube music etc.
So has anyone had any experience with this? Has anyone gone down this path before? Any suggestions or ideas would be much appreciated

Have you get this resolved? i have the same question about it.