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Old 10th January 2013, 05:26 PM   #71
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Quote:
Originally Posted by metalsculptor View Post
Audio D/A converters have a passive filter with a rolloff frequency of less than 22kHz to avoid aliasing.
You sure about that? Even after the eighties?
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Old 10th January 2013, 06:46 PM   #72
AKN is offline AKN  Sweden
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Hi marce,
Yes, it is important.
15 years ago I returned to school and studied PCB design and EMC at the university. The latter opened a whole new world for me. Highly recommended!

Btw, not all supplies are equal even if the same, Linear/SMPS.

Recently I needed a +/-15V supply for a application. I found a linear Mascot stabilized +/- 15V 250mA in my storage. Perfect, or? Well, lets measure. Pic1, load 100mA - not so good! Opened it up and the PCB design were a disaster. Caps on stubs. Currents in tracks also used for reference.
Quick fix just to prove current design wrong. Cut two tracks and three wire jumpers pic2. Result: Pic3 explains it better than words. Of course, more to improve but that's the job for a new PCB.

mascot.JPG

mascot_modding.jpg

mascot_mod.JPG
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Last edited by AKN; 10th January 2013 at 06:58 PM.
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Old 10th January 2013, 07:14 PM   #73
qusp is offline qusp  Australia
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yeah marce: i'm keenly waiting for hochopeper's copy of that to arrive so I can attempt to scan all 200 pages or whatever lol.
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Old 11th January 2013, 06:58 AM   #74
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Quote:
Originally Posted by analog_sa View Post
You sure about that? Even after the eighties?
Yes A quick check to confirm just in case my memory was failing me.

There is no escaping Nyquist, over sampling just make it possible to get good results with a single pole filter on the D/A convertor, which has both a cost and a phase error reduction advantage.
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Old 11th January 2013, 07:35 AM   #75
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Not arguing about Nyquist but only about your stated figure "of less than 22kHz". You reckon all these 96/192/384kHz recordings are a scam?
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Old 11th January 2013, 07:44 AM   #76
marce is offline marce  United Kingdom
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Qusp, 843 pages including index
AKN, got to admit when called in to sort out a PCB thats failing EMC or just problematic, it is usually a SMPS that is layed out incorrectly, often by both dedicated PCB designers and engineers that lay there own boards out (often the worse layouts). This is a big problem even with reference designs, numerous application notes and design guides. I have discussed this with SMPS application engineers from the likes of TI and Linear, and it does seem to be a big problem, bad SMPS layout!!! I believe it is this that gives SMPS a bad name. Once where I worked we outsourced from a distant shore some SMPS,s, the samples were perfect, the container load that we recieved were so noisey we had to scrap all of them. Unlike linear PSU's SMPS;s are not forgiving of bad layout.
I do get frustated with bad layout of SMPS's because basicly the design and layout rules are simple.
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Old 11th January 2013, 07:51 AM   #77
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Originally Posted by marce View Post
Qusp, 843 pages including index
I can hardly wait

On backorder with the mob in Aus so I think 4 or 5 weeks away from my eager hands
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Old 11th January 2013, 07:55 AM   #78
qusp is offline qusp  Australia
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haha hmm methinks I will need to prioritise, why the hell dont they offer an Ebook version? or do they?
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Old 11th January 2013, 07:56 AM   #79
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If they are the recordings with the DRM, most certainly a scam of a different kind not very common so I didn't even consider them
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Old 11th January 2013, 08:40 AM   #80
qusp is offline qusp  Australia
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huh? were talking about an electronics design EMC manual over 800 pages. or you are talking to someone else?
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