MPD is not offering any audio output

[eragefe]

Yes? No? something else?

BR G

[ACX]

RuneAudio currently doesn't output to HDMI on the BBB, but we are working on it for those who need this feature.

[eragefe]

Thanks for your answer.

HDMI itself is not interesting. The reason I am asking is because enabling that will give you I2S on the header.
I have done several DAC constructions over the last years and I can tell you the sound is remarkable better when you use a ground isolated I2S directly from soc.
I have tried that with other images on BBB and it sounds much better than anything else by far.
You have done a remarkable nice job with the software (the best out there) so BBB+runeOS+I2S+somthing like dual mono PCM1794 +NOS mode +ground isolation +clock resync +discrete class A buffer/output stage could be the best total solution for many many years.
The USB BUS itself has construction issues from the beginning and in my eyes and ears are not the best way to transport sound. Some USB DACs sounds pretty decent but I believe that people like you and me are seeking for the highest end regarding audiophile sound.

BR G

[ACX]

I absolutely agree with you on considering I2S as THE way to go. We are currently focusing on I2S output on the Raspberry Pi, and BBB will be the next one to receive the treatment.
Would you please consider contributing to this feature with your knowledge? We are very busy in these days with the rework of the RuneUI (next release will introduce huge improvements on that front), and a help would speed up the development.

[eragefe]

It feels like you just opened Pandora’s Box.
1. Why beaglebone and not RPi ? Everything that has with your audio signal to do is related to ground. Your ground should be solid rock 0vDC 0vAC. My first thought was let’s do some measurement’s to the RPi ground. Placed the probe between a ground point near the HDMI connector and the I2S header ground pins.
Obviously you have high frequency ripple generated from the CPU and other guys on the board.
Ok not so unusual let’s start MPD playing something.
What a …. We almost have music between ground point and ground point on the same device.

Solid rock Nooot. Those devices are not made to play audio primarily.
I can see the same problem on BBB but the amplitude is 20 times lower.
That’s why I am talking about ground isolation
2. You hear often people talk about digital signals like “a zero is always zero and one is always one.” BUT your audio signal consists of wordclock, bitclock and data and for sure zero’s and ones are always zero’s and ones there but the most important is the relation between them in time.
There you have the problem.
That’s why I am talking about resync/reclock.
I could continue forever but people would stop reading. I can take more details on another post.
I will post here the layout of a pcb I recently made that accepts both RPi and BBB and has all those features I am talking about.

BR G

[ACX]

You don't have to persuade me about that, really I like BBB a lot, first because it's a fully open source board, and then for the build quality. We are focusing on Raspberry Pi in these days because it's the most popular platform and because there are already some nice projects of I2S DACs around that we would like to support as soon as possible (we are talking about them around the forum). I'm aware of the Pi's limitations and I'm really interested in seeking the best possible sound quality from BBB.

[eragefe]

As you understand I am a hardware guy.
I have compiled some kernels for BBB/RPi/cubieboard but software is not my strongest area.
Here comes the layout I promised to post.
I hope you not misunderstood me. I think that RPi is a fantastic little thing.
But we have to know the issues around it if we will succeed to go around them.

BR G

[ACX]

That design, together with the compatibility with Raspberry Pi and BeagleBone Black, is really interesting for anyone who wants to get the highest sound quality from both boards.
Are you considering to put it in production someday in the future?

[eragefe]

Yes Its only few weeks away.
The prototype sounds very nice. Together with RuneOs could it be an outstanding streaming solution.

BR G

[dafart]