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Old 5th February 2014, 02:40 AM   #1
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Default Building an open embedded audio applicance.

For quite some time I have been interested in streaming direct from an embedded system to an Asynchronous DAC.

I did this many moons ago using a beaglebone, and later beaglebone black, but while the results were great - I was not entirely happy with the complexity. I basically had a custom kernel and ALSA modules. In short more than I was happy to share, and it took far more effort than the average Joe would care to undertake.

Recently however the folks behind Raspbian and especially Florian Meier with his contributions to I2S modules have made me take a much closer look at the raspberry pi - particularly "model B - revision 2". The addition of P5 and the newest Raspbian and Volumio builds make it possible to have an incredibly good I2S based music appliance by simply adding a great DAC - such as the Buffalo III-SE - which works perfectly - but you could just as well use any asynchronous I2S input DAC.

Using the raspberry pi with the B3SE is very simple. I have tested two scenarios - each with distinct advantages.

First pi -> DAC direct.

This is really simple:

just wire P5 to the DAC appropriately - as show in the attached picture. Pin 1 is indicated on the rpi by the square pin. And P5 is located right next to P1 (directly below with P1 oriented at the top).

The best news is once configured you can use the pi as an airplay receiver (with a mac) for audio (at 44.1khz) and as a direct audio appliance at up to 192/32bit sample rate (the limit of ALSA at the moment).

I have mine streaming directly from NAS (an ASUS RT-AC66U with a USB SSD drive) at up to 192Khz sounding superb! No complaints. The sound is incredible.

The second method I will introduce if there is enough interest.

Here is detail you will want if setting up Raspbian, or Volumio for B3SE.

make your /etc/modules file looks like this:

Code:
snd_soc_bcm2708
snd_soc_bcm2708_i2s
bcm2708_dmaengine
snd-soc-pcm1794a
snd_soc_rpi_dac
I am happy to help anyone who has any further questions on how to make it work.

You won't be disappointed with the results.

I have developed two different USB -> I2S modules, and I have yet to find any reason to use one of those over this much more direct approach. Especially for the Buffalo III-SE.

Cheers!
Russ
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Last edited by Russ White; 12th February 2014 at 01:24 PM.
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Old 5th February 2014, 03:00 AM   #2
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Edited because i forgot to attach the P5 image.

I should be forgiven because I am listening to some incredible music at the moment and it is hard to keep the mind on posting...
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Old 5th February 2014, 05:32 AM   #3
miero is offline miero  Czech Republic
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Quote:
Originally Posted by Russ White View Post
I have developed two different USB -> I2S modules, and I have yet to find any reason to use one of those over this much more direct approach.
What about jitter? Or ESS DPLL/ASRC will take care of that well?
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Old 5th February 2014, 09:31 AM   #4
amix is offline amix  Hungary
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I hope Russ doesn't mind, also, I don't want to hijack this thread, but did anyone have the chance of comparing what Russ described here with the DAC here: http://www.hifiberry.com

Bye, Andreas
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Old 5th February 2014, 09:35 AM   #5
4est is offline 4est  United States
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This is great news Russ, thank you! I haven't a clue as to how the programing works, but I am interested in this and your other option.
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Old 5th February 2014, 09:54 AM   #6
DQ828 is offline DQ828  Australia
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Hmm, I can feel another project coming on, watching with interest.

Could you make stand alone active speakers this way, you would have to stream 1 channel to each speaker?
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Old 5th February 2014, 10:00 AM   #7
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This is very interesting, could you elaborate on the jitter performance? The pi is known for having less than great jitter output.
Can the pi be powered from the 5v placid psu or should a separate psu be used for the pi?

Last edited by MASantos; 5th February 2014 at 10:19 AM.
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Old 5th February 2014, 10:02 AM   #8
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This is really peculiar - just yesterday I was googling on how to use one of embedded systems (Raspberry or BeagleBone) with my BIIISE's, omitting PC and USB, and now here is Russ's post

Russ, did you try outputting DSD?

Thanks,
Fedor
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Old 5th February 2014, 10:44 AM   #9
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It would be interesting to point volumio/runeaudio/raspbian developers to this thread so they could integrate the code Russ detailed above in the releases. This Way the users would not have to code anything, which can be quite daunting for most people, myself included!

Russ,many stability, gapless playback, pop sounds or noise issues?
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Old 5th February 2014, 11:11 AM   #10
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Originally Posted by amix View Post
I hope Russ doesn't mind, also, I don't want to hijack this thread, but did anyone have the chance of comparing what Russ described here with the DAC here: HiFiBerry | HiFi for the Raspberry Pi and more

Bye, Andreas
Have a look here, this one seems better to me vs the one shown in your link :
RPi-DAC - High Quality DAC

tjaekel is member here

Regards

Phil

Last edited by korben69; 5th February 2014 at 11:14 AM.
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