My BeagleBone Black + integrated DAC music server / streamer project page

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At the Computeraudiophile.com site an article was published how to use a BeagleBone Black compueter as music server/streamer.

It triggered me enough to buy one and I have it running with MPD playback software and the MPad App for control.

I will build an enclosure with two stacked compartments which will hold the BBB board, the DAC PCB (stripped Lindemann USB DAC) and a power supply board.

In the bottom part I will put the BBB server and in the upper part I will put the Lindemann USB DAC (bare PCB only) and a custom built power supply.
The supply will have 3 seperate outputs (DAC / BBB / USB) with multi-stage filtered RC network and shunt regulator for stable and clean 5Vdc out.
External power is through a brick type power supply which delivers 15Vdc.
I will remove the DAC backplate and LINE OUT connector, put some Neutrik NF2 style chassis connectors in the backpanel, remove the mult-colored LED's from the DAC PCB and mount LED's and selector button in the frontpanel extended via a flatcable.

An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.


The BBB is shown at the same spot as the DAC PCB but it is actually mounted in the lower part of the cabinet.
I can use an USB cable of only few cm's through the centre plate and solder the signal leads (USB power comes external) direct on the corresponding pins of the XMOS board connector for shortest signal path bypassing the dedicated USB input connector completely.

An externally hosted image should be here but it was not working when we last tested it.


The BeagleBone will draw max 460 mA so I set the LM317 current source a little higher at 570 mA.
Because the average current draw by the BBB is likele to be much lower I dit not really calculate 150% x 460 = 690 mA.
During playback and streaming I still will have plenty headroom left even with "only" 570 mA.

The current draw by the DAC and USB will be more stable so here I will calculate the full 50% extra for the current source.

Although it is designed that way the TI ARM processor can be quite warm to the touch.
The first modifications already are already done: lowering thermal stress for 24/7 operation ;-)
From an ATI graphic card from my old PC I had some adhesive heatsinks which were meant for additional cooling for the overclocked RAM chips.
They fit nicely on the processor and RAM / MMC memory.

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


This will be an ongoing project page so do not expect regular updates weekly because I still have to collect all the parts before I can build it.
Besided that I also have to tweak the buffer settings in the MPD config files to get the best and fluent playback.

P.S. I know I will probably lose my warranty / manufacturer support on the Lindemann DAC ;-)
 
The Lindemann DAC is fitted with 3 pieces of 4-pin multi-color (RGB?) leds.
The color shown represents the sample frequency or "not connected" state.

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I decided to take it another route and make a new LED design using the available signals from the DAC PCB run them trough a set of AND/OR ports and make it look (and function ;-) like this:

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Today I had some time to continue with my project.
Determine the mounting position of the DAC board and BBB on the centre plate af the aluminium enclosure.
The BBB will be hanging upside down in the lower compartment.

Using PC parts (the studs on which you mount the mainboard in a case) I thought it would be neat and look professional.
I measured the thread of the studs which appeared to be M3. I have cutting tools from M4 - M10 so I had to buy a M3 tap too.

I first drilled the holes for the BBB studs but during this porcess I realised I only had 4 of these studs ... the silver ones.
All other were the brass models which had different thread. Measuring these I guess they are 1/8 inch (= approx. 3,2 mm) for which ofcourse I did not have any cutting tap.

I drilled the holes for the brass studs with 2,5 mm too and used the drill too have the studs cut them selves into the aluminium with some pressure which worked quite well.

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The power supply PCB's will be installed with the brass studs too. I will make 2 dedicated PCB's on each side for each component.

When drilling the holes in the edge of the DAC PCB I hoped I did not destroy any traces which I might have overlooked but now I am writing this topic my DAC is playing nicely installed on the bare aluminium so everything is fine.

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As an anti-vibration solution I have a piece op adhesive bitumen which I cut to fit and attached to the centre divider and top and bottom plate.

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As I will not use the USB power from the BBB I cut a standard USB cable and use only the signal leads.
The 5 Volt needed for the USB receiver and XMOS chip will be clean regulated from the custom power supply.

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The pins marked in red are the USB signal pins so the green/white leads will be soldered directly to these pins.
The pins marked in yellow are the USB power pins. Also the USB power will be soldered directly to these pins.

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Hi Kimbo,

It has been some time but I have made some progress ...

I have built the power supply boards and some more.
I also soldered the short USB cable to the receiver board of the DAC.

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During testing when measuring the stability op the voltages I short-circuited the USB power at the receiver board by accident when my measuring pin from my DMM moved a little. After that the system still functioned but after a few power on/off cycles the DAC refused to lock to the USB input. After some tests I concluded the USB output was faulty ... not surprising after all.
I needed a new BeagleBone Black ... :-(

Ordering a new one had a delivery time of some weeks. Apparently the BeagleBone was very popular and the seller was out of stock. A few weeks later I got the new one so I could finally continue.

After installing the new BBB I first used an external USB cable (the earlier with my HTPC used Wireworld Starlight 2 mtr length) but when everything played fine again I soldered the silver USB cable direct to the USB receiver board of the DAC and WOW !! ... what a difference that made. Much more detail and the acoustic ambiance in the recodings was much more present.

The height of the power supply boards made me realise the aluminium side profiles would be to low to fit.
I had some wood prepared with some grooves to hold the three aluminium plates.

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For max. RFI protection I covered the inner panels with aluminium foil.

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On the XMOS board are some crystal oscilators. These oscilators are high frequency so they probably emit high frequency radiation.

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Being very close to the analog output stage I decided to make some screening made of aluminium foil covered with tape for electrical isolation. It is like a bag which I slip over the XMOS board.

At this moment the streamer is running fine without any issues for more than a month now. Need to paint the wood and make a nice backpanel for better fitment of the cable entries but am happy with the results so far.

If you have any questions feel free to ask.
 
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