AKM AK4399 DAC PCB+IC on Ebay - diyAudio
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Old 7th February 2013, 01:27 AM   #1
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Smile AKM AK4399 DAC PCB+IC on Ebay

Hi,

I'm about to start building this, and I've seen people show some interest so I thought I'd start a build thread.

I've put the information on my blog for anyone who's interested :

http://myl8test.wordpress.com/audio/ak4399-dac/

cheers,

Tom

Last edited by KlipschKid; 21st February 2013 at 02:57 PM.
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Old 7th February 2013, 08:23 AM   #2
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Great pics!

This is a very interesting DAC. According to the data sheet the AK uses 3 wire SPI for serial/software mode (needed for DSD). Do you plan to use it in PCM/hardware mode or serial/software?
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Old 7th February 2013, 08:43 AM   #3
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Thanks - I think it could be quite easily hacked for serial control, but I'm gonna stick with parallel.

Just a quick look and you can probably see a few routing issues - hopefully I can fix them - an op amp power line runs between the pads for 470R on both channels. It's okay that they cross perpendicular, so there's little chance of any induced problems, but I'd like to improve that. Maybe it'll be as simple as using a through hole resistor mounted on the other side. And the power rails for the DAC run perpendicular across the DAC's analogue output - between the C1-C4 mounting points. On the plus side, a continuous ground plane on the other side is very welcome.

Did I miss anything else that needs to be improved ?

I'll need to work out the Q of the lpf filter too.

cheers

Last edited by KlipschKid; 7th February 2013 at 08:54 AM.
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Old 7th February 2013, 12:27 PM   #4
marce is offline marce  United Kingdom
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The PCB layout! Its not the best.
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Old 7th February 2013, 01:41 PM   #5
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The terms "ground pour" and "via" spring to mind.

I have some ideas about how to mitigate the C1-C4 and 470R routing. Is there anything else to address ?

It is just for fun - I'll try to build it for very little money. The parts I ordered were just US$8. Are there any other AK4399 diy projects out there ?

cheers
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Old 7th February 2013, 02:09 PM   #6
marce is offline marce  United Kingdom
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Some small package SMD decouplers near the device pins would be advisable the 0.1uF decouplers they have put on will be useless there so far from the device.
Its a pity, with a bit of extra effort they could have made a nice DIY board for people to play with.
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Old 7th February 2013, 02:23 PM   #7
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Thanks. I'll try to do just that.

I think the seller is probably willing to make changes and try to improve the design because he has done this with his other kits, and a better PCB might increase sales. I don't doubt he'll read this thread so if you think it's worth your time, do feel free to give some specific comments. Then again, he could just read all those links you've posted !

I2S and digital signal path - in-line resistors?
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Old 7th February 2013, 02:49 PM   #8
marce is offline marce  United Kingdom
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Cheers for the link, I was trying to find it the otherday as I have lost my source of a lot of those links.
As they are already populating the DAC it would be nice to add the decoupling and possibly a local LDo to supply the DAC, wouldn't add much to the overall cost but would make it a much better option for DIYers especially those with limited experience.

Cheers Marc
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Old 9th February 2013, 01:27 AM   #9
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I agree - a little bit more smd done already so the rest of the design can be through-hole stuff.

I found a really good online lpf calculator here : (Sample)Sallen-Key Low-pass Filter Design Tool - Result -

The AKM result is clearly better. However, for the board's values, changing the shunt cap on the op amp input to 7.5nF or 8nF is an improvement, although the cut off frequency is still quite low ~98Khz.

Here's some of the numbers. The site also gives graphs for transient response etc.

AKM Values :

Cut-off frequency
fc = 18202776.4579[Hz]

Quality factor
Q = 0.439589907374

The system does not oscillate.

And the circuit values on the board have this result :

Cut-off frequency
* * fc = 106386.994045[Hz]

Quality factor
* * Q = 0.5

Oscillation frequency
* * f = 0.00124339799291[Hz]

Last edited by KlipschKid; 9th February 2013 at 01:57 AM.
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Old 9th February 2013, 01:57 AM   #10
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Quote:
Originally Posted by marce View Post
Some small package SMD decouplers near the device pins would be advisable the 0.1uF decouplers they have put on will be useless there so far from the device.
Its a pity, with a bit of extra effort they could have made a nice DIY board for people to play with.
zero distance decoupling capacitor is done like this the limitation is always on the diyer happy diying to all
Click the image to open in full size.
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