BBB - Building a DAC - part 2

RE: BBB - Building a DAC - part 2

clem57 — Mon, 07 Oct 2019 13:53:07 GMT

[mention:b0bc65b9ecdc4307bd967592f00e340a:e9ed411860ed4f2ba0265705b8793d05] do you think this would work on the BB-AI? If you can, please try it out.

Thanks Clem

RE: BBB - Building a DAC - part 2

Former Member — Sat, 02 Aug 2014 17:32:41 GMT

There is a nice discussion of how to add a PCM5102A-based audio device driver to linux: Sitara Linux SDK Audio DAC Example - Texas Instruments Wiki

You can use it "as is" with shabaz's design. This lets you get rid of the pesky BCLK inversion problem, as well as use sample rates other than 48kHz. Of course, to use a BCLK rate that is not a multiple of 48kHz, you need an external MCLK source. If you want the ultimate fidelity, an external low-jitter MCLK source is necessary, but fidelity with the internal MCLK is really pretty awesome. I can barely detect any difference between external and internal clocking on my $10K hifi system. What I hear is that positions of instruments are slightly more clear and precise, and transients like piano notes are more distinct, with the external clock. Don't hold me to a blind testing!

If you wish to supply the MCLK externall just change

ret = snd_soc_dai_set_sysclk(cpu_dai, 0, sysclk, SND_SOC_CLOCK_OUT);

ret = snd_soc_dai_set_sysclk(cpu_dai, 0, sysclk, SND_SOC_CLOCK_IN);

and activate the appropriate pinmux for AHCLKX.

Although this example is based on kernel 3.12.10, I found it quite easy to adapt for kernel 3.15.4. I wish this had been available last Jan., it would have saved me a lot of work.

RE: BBB - Building a DAC - part 2

shabaz — Fri, 01 Aug 2014 19:55:52 GMT

Hi John,

Good stuff! Nice compact board.

RE: BBB - Building a DAC - part 2

Former Member — Fri, 01 Aug 2014 19:25:51 GMT

I taught myself to make PC boards, using the free gEDA tools (gschem and pcb). My first project was a small 1.5x2 inch Beaglebone outboard 2 channel DAC. I'm also using the pcm5102a, due to the ease of interfacing and the small number of external parts needed. The central chip is the DAC and the other large rectangular chip is a crystal oscillator that generates the master clock. I used 3 x 3.3 v regulators with plenty of bypass capacitance, and I cannot detect any trace of digital grunge. I thought that working with very tiny SMD parts would be problem, but actually it is easier than the old way. Fewer holes to drill, and solder bridges are easily fixed using solder wick.

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RE: BBB - Building a DAC - part 2

Former Member — Thu, 29 May 2014 20:16:12 GMT

[mention:b0bc65b9ecdc4307bd967592f00e340a:e9ed411860ed4f2ba0265705b8793d05], very inspiring. I'm attempting to do a pcb for this in Eagle and hitting some snags. Happy to share my output with you if you'd like. Would you consider sharing your layout (front and back)? If that's a big faux pas to ask then I apologize. Amazing work! Thank you.

RE: BBB - Building a DAC - part 2

Former Member — Thu, 15 May 2014 14:16:33 GMT

Hi, I'm unable to download the atached zip file or to see the schematics png files, any way to get them from another source ?

Thanks.

+++

RE: BBB - Building a DAC - part 2

alonzo — Sun, 16 Feb 2014 01:23:38 GMT

oh, so you've disabled it? anyways, thanks for checking.

RE: BBB - Building a DAC - part 2

alonzo — Sun, 16 Feb 2014 00:07:47 GMT

hi, may i ask a question? -- the bitclock inversion thing, has this been solved? or is there any hope it will?

thanks!