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Old 14th November 2012, 05:36 AM   #11
i2k92 is offline i2k92  Indonesia
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@SandyK : thanks for the schematic, great for the poor like me who drool over those expensive SOTM filters.
How critical is the component value selection for that circuit ? I'm having difficulty to locally find 4700uF low esr caps , can I use 2x2200uF in parallel without affecting the effectiveness of the filter ?
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Old 14th November 2012, 06:00 AM   #12
sandyK is offline sandyK  Australia
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i2k92
That should be fine. The main thing is to make sure that you balance the electro types between low ESR and normal types, otherwise the sound can become too detailed and fatigueing.I realise that we are talking about digital here and it shouldn't matter, but it does. In my tests with Martin Colloms from HiFiCritic magazine, the C-L-C rip of "Dire Straits- Private Investigations" was judged to sound more like the master that M.C. had heard.
The findings were published in HiFiCritic Vol6 No.1, although far more detail was given in various threads in HiFiCritic Forum. I am presently getting even better results when using a modified version of an old John Linsley Hood PSU Add-on design (A.K.A JLH Ripple Eater) which has a simulated capacitance of around 1Farad and a typical noise level of approx. 4uV.
Alex
P.S.
I will not be responding to any posts about why all of this is impossible.
As far as I am concerned, Martin Colloms is among the most respected and qualified of the technical writers and reviewers, and he had 6 separate Blind A/B/A/ 3 minute sessions during this lengthy investigation. I chose to contact him after around 4 years of investigation in this area, in which there were far too many sarcastic replies in DIYAudio and a couple of other forums.
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Old 14th November 2012, 10:52 AM   #13
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Quote:
Originally Posted by hochopeper View Post
At that price, I would rather Ian's FIFO (a project developed on these forums) with his new isolator board on the i2s lines and reclock the i2s after the isolator. In theory should make the system almost transport agnostic and variations on the computer side will have minimal impact.
I like the "In theory" and "almost" most.

Though I do agree.

The first and most cheapest step would be to count on a quality Toslink implementation - which keeps all the noise out. It needs to be that good that the receiver is able to lock to the stream. I'd prefer that one over e.g. Adnaco USB over fiber isolators.

I don't think I2S isolators are required. Those come with their own problems.

Jitter/timing variations need to be covered on the DAC side by a reclocker.
That's the key challenge.

The DAC should then be run from a battery, to avoid ground/noise loops
through the backdoor.

I consider it waste of time and money to concentrate on the transport. Though I did do it by myself for years.
You'll never manage to get the transport under control.
And don't forget. You'll never be able to tweak all your transports (PC, phones, tablets, squeezeboxes) the same way.
Every HW/SW swap/change can make a difference. That'll drive you nuts.
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Old 14th November 2012, 11:16 AM   #14
marce is offline marce  United Kingdom
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A guide to filter design, ore effective at the frequencies likely to be present in the digital domain and should serve as an introduction, a quick search on google will provide many links to information on filtering.


http://www.ti.com/lit/an/swra064/swra064.pdf

Filter Calculator
Chebyshev Pi LC Low Pass Filter Calculator

And if you want to get serious about filter design...
Electronic Filter Design Handbook, Fourth Edition McGraw-Hill Handbooks: Amazon.co.uk: Arthur Williams, Fred J. Taylor: Books
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Old 14th November 2012, 12:23 PM   #15
JLOP is offline JLOP  France
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Thanks Marce for the info

The greatest challenge for my understanding is prioritizing the different efforts that have to be made to mitigate noises in a "Big Picture" with some measurement data if possible
- there are different sources (PS, digital components themselves, ..)
- there are internal cables, aerial transmitting modes, external cables
- there are digital parts, DA convertors, analog parts, HDD, ventilators, Optical DD,... all the mess inside a pc and USB=>SPDIF convertor

I dunno where I could get that faster than training few years as design engineeer (was trained in EE but long ago and practice more in IT)

BR
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Old 14th November 2012, 12:43 PM   #16
qusp is offline qusp  Australia
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a hint, dont start with using CLC filters to improve EAC audio rips...
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Old 14th November 2012, 12:48 PM   #17
jtwrace is offline jtwrace  United States
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This is very simple and effective Felix project see also http://www.audiocircle.com/index.php?topic=18443.0

PCB isn't needed either. Very important to use "X" rated caps though.
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Last edited by jtwrace; 14th November 2012 at 12:54 PM.
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Old 14th November 2012, 01:10 PM   #18
marce is offline marce  United Kingdom
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I dont want to disapoint anyone, but owever noisy you percieve your PC to it will work as will most competently designed digital systems, that is the beauty of digital. Now I know that no doubt there are some audiophile who may think otherwise but they are misinformed or ike peptuating the myths that are coming out regarding digital systems and digital design. Most of these I suspect , the nearest they get to digital design is pressing the on button on their PC.
If you are so concerned about the noise getting to your DAC galvonic isolation is the only way.
As I stated earlier, there are numerous filtering circuits built in to digital equipement these days so adding the SOtM overpricedfilters aint gonna do a lot more.
So isolate your DAC, have the bare minimum digital on your DAC board and thats the best you can do.
As to digital it is very tolerant of noise that is why it is so prevelant these days,and most designs that employ DDR memory interface are simulated these days to ensure that both the signal integrity and EMC performance are at acceptable levels, then equipement is also tested.
If you wanna get an understanding of all this there are many links in the attached text file that will lead you to signal integrity, EMC sites and design guides.
I would reccomend looking at Ians stuff linked to earlier
Attached Files
File Type: txt PCB related links.txt (5.1 KB, 88 views)
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Old 14th November 2012, 08:55 PM   #19
sandyK is offline sandyK  Australia
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Quote:
I dont want to disapoint anyone, but owever noisy you percieve your PC to it will work as will most competently designed digital systems, that is the beauty of digital.
In Marce's "perfect" little digital world, this shouldn't be possible either.
Yes, I am aware that he has designed PC Motherboards.

Cookie Marenco is an award winning record producer and leading exponent of DSP recordings.
Quote:
"If you can't hear the difference between an original CD and a copy of your CD, you might as well give up your career as a tester. The difference between a reconstituted FLAC and full size WAV is much less than that, but it does exist."-Cookie Marenco. cookiemarenco.com
Additional reading for those who like to listen for themselves, rather than blindly accept everything they are told about how perfect digital is.

Sound is better from uncompressed downloaded files?

HiFiCritic Vol.6 No.1 by Martin Colloms ( Various HiFiCritic forum links can be provided on request via PM for those with open minds,)

The Absolute Sound 220 and 221 from earlier this year.
Computer Music
Audio Quality, Part 3
"Is FLAC a Fraud" Charles Zeilig,Ph.D and Jay Clawson.

Anyway, I am now out of this thread. I simply provided a possible answer to the OP, as something to try for himself.
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Old 14th November 2012, 09:09 PM   #20
marce is offline marce  United Kingdom
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It isn't perfect for noise when you are converting to analogue, though that is why I promote isolation of the DAC from the PC source, and to limit the digital circuitry in the DAC, no SMPS's, LDOs etc I know we disagree, but getting data from a to b has been worked on for decades now, and just the speed and reliability of the internet, mobile communications etc these days, never mind the amount of digital data worked on each day on millions of devices. i am not going on about FLAC I am refering to digital signal transmission. Fior the record I use uncompressed WAV.
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