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Old 8th August 2014, 05:07 PM   #11
Toshen is offline Toshen  Ukraine
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Quote:
Originally Posted by AndrewT View Post
All the in/outs must be located close together at one edge of the PCB.
Are any benefit to place analog and digital in/outs together?
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Old 8th August 2014, 08:55 PM   #12
AndrewT is offline AndrewT  Scotland
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I would need to read Ott again.
But one thing I do know:
I do not know enough to design a planed PCB.
__________________
regards Andrew T.
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Old 9th August 2014, 07:29 PM   #13
dmills is offline dmills  United Kingdom
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The key things to remember is to always try to minimise current loop areas, especially when fast signals are concerned.

Lay the board out as if you were doing a split plane, but don't actually split the plane is generally best practise for most things.

I would critique that board as trying to be overly pretty (especially with those long curved tracks leading to vias to the ground plane), a via right next to the pad is almost always better then one 10mm of skinny trace away.

Get some decoupler ceramics right at the pins, and where possible connect them to the relevant pins without involving a via (Going say from a part on layer 1 -> via to ground -> via to layer 1 > decoupling cap ground end is much worse then part on layer 1 -> decoupling cap for all that both nets have the same names).
Quite often you will find that a sensitive part is designed to allow a 0603 or similar cap to be conviniently placed with the power and ground pins in reasonably good alignment, take advantage.
Those enormous thru hole caps are mostly a wate of time for HF decoupling, a 100nF or so X7R 0603 or even 0805 or 1206 will stomp all over them in effectiveness simply due to smaller loop area and hence less inductance.

the advantage of placing all the IO on the same edge of the board is that everything has the same ground and is thus less likely to radiate once the cables get outside the case.

I worry about the missing reconstruction filter parts, without it you still have significant energy up into the RF on those analogue outputs just begging to get into things.

Regards, Dan.

Last edited by dmills; 9th August 2014 at 07:33 PM.
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Old 14th August 2014, 04:51 PM   #14
Toshen is offline Toshen  Ukraine
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Here next revision
Click the image to open in full size.Click the image to open in full size.

Quote:
I worry about the missing reconstruction filter parts, without it you still have significant energy up into the RF on those analogue outputs just begging to get into things.
Investigate this now=)
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Old 22nd August 2014, 11:01 AM   #15
Toshen is offline Toshen  Ukraine
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Can anybody link reconstruction filters article? How its work, how to design filter, examples etc. Thanks a lot.
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Old 26th August 2014, 03:32 PM   #16
Toshen is offline Toshen  Ukraine
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Are anybody can tell where I can find literature about reconstruction filter: how to design it, where is it used in DAC, etc ? Please! I was unable to find literature in Internet
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Old 26th August 2014, 03:45 PM   #17
marce is offline marce  United Kingdom
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quick answer I believe it is a low pass filter to get rid of the hf noise and conversion steps...search this forum there are threads on these filters.
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Old 26th August 2014, 04:04 PM   #18
Toshen is offline Toshen  Ukraine
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I thought that low pass filter used for cut the signal to frequency range that subwoofer can play. And reconstruction filter used to make the signal smooth (as I understand DAC IC has output signal look like a stair).
Is it right?
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Old 26th August 2014, 04:10 PM   #19
marce is offline marce  United Kingdom
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Same thing, the steps are caused by the high frequency content of the output, filter that out and your left with the audio spectrum. There are others that can discuss this in more detail than I can, but that is the basics of a reconstruction filter.
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Old 26th August 2014, 04:21 PM   #20
Toshen is offline Toshen  Ukraine
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Thank you, that is what I needed to find out.
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