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Old 8th May 2012, 09:08 PM   #41
BFNY is offline BFNY  United States
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I've been down this road before, and thought about it a great deal. This take on the matter from the link above pretty much sums up what I agree with
Calculations for PWB Trace Termination and Reflection values
"Source Termination may effect the rise time of the signal because of the RC time constant [R of resistor, C of the cable]. The driver is specified with a rise time based on some unit load [say 10pF], the rise time will be reduce to the R * C time constant with the series resistor. As the rise time is decreased the over all current demand from the driving pin is also reduced. Reducing the rise time has one benefit, reducing the Instantaneous current demand on the driver [reducing ground bounce and EMI] A series terminated line does not stop reflections [the load is still not terminated, un-matched], but it does reduce [damp] the amplitude of the ringing."

With digital audio, especially at the mixed signal device (DAC chip) you need to do all possible to avoid digital contamination of the analog output. The chip die wire connections to pins are very close, so you want to reduce coupling effects from pin to pin. And the effects of ground bounce from fast transitions can also create DAC conversion problems.

In my opinion, you need to examine which clock and data lines need sharp transitions (those that effect data conversion timing, i.e. jitter) and which don't. By fast transitions, I'm referring to fast rise and fall times.

In general, my experience is you should load the data frames reliably, but use the slowest transition time possible to get the job done. This approach also requires you to research what clock reference the DAC chip uses to control/trigger the conversion timing - it's either the L/R clock or bit clock. That one needs to be fast, (but not ringing) the others should be as slow (longer rise and fall times) as possible, to still work.
This edge speed is controlled by the value of the series resistors.
This is not a textbook approach, it's what works for me in this particular application. You need a decent scope (2GS/s or faster, 500MHz) and decent probes (500MHz active or better) to really observe what's going on.
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Old 9th May 2012, 05:43 PM   #42
marce is offline marce  United Kingdom
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The main skill in designing PCB's is component placement, the success of the design depends on good comp placement, the rest should then follow. Autorouters, very very rarely use them, may use them interactively for little areas and to get a metric on placement but that is it.
Some analogue digital design links, mainly relating to ground and how to placethe components...
http://www.hottconsultants.com/pdf_f...ixedsignal.pdf

AES 2006 ? Henry Ott, Saturday - Anablog | Blog on EDN
http://www.hottconsultants.com/pdf_files/aes-2007.pdf
http://www.elmac.co.uk/pdfs/Lord_of_the_board.pdf
An intuitive, practical approach to mixed-signal grounding
http://focus.ti.com/lit/an/sbaa052/sbaa052.pdf
http://focus.ti.com/lit/ml/slyp167/slyp167.pdf
http://www.ieee.org.uk/docs/emc1206a.pdf
http://www.icd.com.au/articles/Split...s_AN2010_6.pdf
http://www.analog.com/static/importe...0Grounding.pdf
http://www.analog.com/static/importe...als/MT-031.pdf

Common Mode Ground Currents

PCB Stack-Up - Part 6
Tech Tips

Analog Devices: Analog Dialogue: Ask The Applications Engineer - 12

http://www.ti.com/lit/ml/slyp167/slyp167.pdf


Twisted pair cables

And some general info on PCB design, the misc section has a couple of tutorials...
http://www.elmac.co.uk/pdfs/Lord_of_the_board.pdf
IEC 60950 Glossary
Star Grounding Wars
http://www.cvel.clemson.edu/Presenta...Decoupling.pdf
PCB007 Quiet Power: Resonances in Power Planes
PCB007 Quiet Power: How Thin Laminates Suppress Resonances
PCB007 Do Not Perforate Planes Unnecessarily
http://www.ipblox.com/pubs/DesignCon...Weir_color.pdf
http://electrical-integrity.com/Quie...ietpower-6.pdf
http://electrical-integrity.com/Quie...ietpower-7.pdf
http://electrical-integrity.com/Quie...ietpower-8.pdf
http://electrical-integrity.com/Quie...ietpower-9.pdf
http://www.electrical-integrity.com/...EPEP98_DET.pdf
Ground Pours: To Pour or Not to Pour?
http://www.goldphoenixpcb.biz/pdf/Lo...Decoupling.pdf
beTheSignal - BTS-305 Battling Ferrite Superstition
http://www.speedingedge.com/PDF-File...ance%20(2).pdf
MIL-STD-461: Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment - Advanced Test Equipment Rentals
http://www.sigrity.com/papers/Power%...ber%202009.pdf
http://alicedcs.web.cern.ch/alicedcs..._Grounding.pdf
http://hephaestusaudio.com/media/200...-for-Audio.pdf


http://www.nalanda.nitc.ac.in/indust...p/slyt012a.pdf
http://focus.ti.com/lit/an/slyt026/slyt026.pdf
http://focus.tij.co.jp/jp/lit/an/slyt319/slyt319.pdf
http://focus.ti.com/lit/an/slyt051/slyt051.pdf

http://www.designcon.com/2010/DCPDFs...ee_Ritchey.pdf
http://www.speedingedge.com/PDF-File...ance%20(2).pdf
Magnetism: quantities, units and relationships
Grounding and Shielding Audio Devices


http://focus.ti.com/lit/ml/slyp167/slyp167.pdf
http://www.e2v.com/assets/media/file...s/doc0999B.pdf
Printed Circuit Design & Fab Magazine Online

EMC Testing

First Link Requires Login
EMC Information Centre

http://www.compliance-club.com/pdf/EMCTestingPart1.pdf
http://www.compliance-club.com/pdf/EMCTestingPart2.pdf
http://www.compliance-club.com/pdf/EMCTestingPart3.pdf
http://www.compliance-club.com/pdf/EMCTestingPart4.pdf
http://www.compliance-club.com/pdf/EMCTestingPart5.pdf
http://www.compliance-club.com/pdf/EMCTestingPart6.pdf
http://www.compliance-club.com/pdf/EMCTestingPart7.pdf
EMC Design
Design Techniques for EMC
Design Techniques for EMC: cables and connectors
EMC Compliance Club – Design Techniques for EMC. Part 3 Filtering and Suppressing Transients.
Design Techniques for EMC - part 4
PCB DESIGN TECHNIQUES FOR LOWEST-COST EMC COMPLIANCE
Design for EMC Part 6: ESD, dips and dropouts, etc.


PCB Checklist


EMC Compliance Club – Design Techniques for EMC Part 0 Introduction & Part 1 - Circuit Design and Choice of Components (SECOND PART)
EMC Compliance Club – Design Techniques for EMC Part 2 Cables and Connectors (first half of part 2)
EMC Compliance Club – Advanced PCB Design and Layout for EMC Part 6 - Transmission Lines - 3rd Part



EMC Compliance Club

Ground Loop
Ground loop problems and how to get rid of them

MISC
http://electronica.ugr.es/~amroldan/...esignators.pdf
http://www.ucamco.com/public/RS-274X...ion_201012.pdf
http://www.downstreamtech.com/suppor...Simplified.pdf
http://pcbtalk.com/data/upload/Desig...anced_PCBs.pdf
http://www.pcb3d.com/uploads/PCB_Des...on_Process.pdf
http://www.alternatezone.com/electro...torialRevA.pdf
http://www.dnu.no/arkiv1/The%20CAD%2...e%20Future.pdf
http://www.ece.unh.edu/courses/ece71...0Libraries.pdf
http://www.smtnet.com/library/files/...rid-System.pdf
Screen and stencil printing
http://www.rakon.com/Products/Public...SCILLATORS.pdf
http://www.analog.com/static/importe...als/MT-008.pdf
Right the First Time

RF
YO3DAC\Home Page
http://www.intelliconnect.co.uk/wp-c...ncy-Chart1.pdf

He He
http://www.edn.com/contents/images/243231.pdf
Printed Circuit Design & Fab Magazine Online

Return currents#2
http://www.oocities.org/timfoo6143/P..._Singapore.pdf
http://www.pcbcarolina.com/images/Pr...use_of_EMI.pdf
Trace Inductance


Calculators 2
Inductance Calculator


De-coupling
http://www.pcbcarolina.com/images/01...s_Debunked.pdf
Decoupling
http://www.ewh.ieee.org/r4/se_michig...ecoupling3.pdf
http://web.mst.edu/~jfan/slides/Archambeault1.pdf
http://www.ece.rochester.edu/users/f...I_06_Decap.pdf
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Old 9th May 2012, 05:47 PM   #43
marce is offline marce  United Kingdom
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TXT document of links above as some have been cut down when cut and pasted...
Attached Files
File Type: txt PCBlinks.txt (5.1 KB, 63 views)
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Old 11th May 2012, 09:51 PM   #44
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Quote:
Originally Posted by marce View Post
TXT document of links above as some have been cut down when cut and pasted...
marce, Thank you for this super extensive list!!!!
Hope I can get around one day to reading most of them hehe.

Really good references there
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Old 12th May 2012, 07:24 AM   #45
marce is offline marce  United Kingdom
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Just pick the relevent info you require, the rest is there for future reference. I put together the list as a compilation for another forum on PCB design, as the same questions came up again and again from people new to PCB design, so it covers most of the topics that were asked about, and provides some reference data for people both new and experienced to follow.
Glad to help.
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Old 22nd May 2012, 12:57 PM   #46
PET-240 is offline PET-240  Australia
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Quote:
Originally Posted by s3tup View Post
Another example of wrong digital design is Twisted Pear products. They use single GND wire for I2S connectors on their boards. This mistake creates horrorous amount of EMC energy, which both kills analog TVs and radios around, and as well denies the whole SQ gain of external DAC thing. To overtake the issue you should use copper foil tape - solder it on both ends directly to PCB near the connector, and wrap the cable with it. Then you'll get both good EMI shield, good ground and good low semi-controlled impedance.
You can't use a short wire to connect the foil to circuit, you'll need to scratch the board to get to the GND layer directly near the connector, and connect the foil directly to it.
G'day s3tup,
Just wondering if you can post a pic or drawing of what you mean as I have a B III from TP, would like to look at what you are mentioning. Sounds like both ends of the foil are soldered to the same ground point on the DAC board and then wrapped over the incoming I2S lines, though this doesn't make sense.

Can you please advise?

Much Thanks,

Drew.
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Old 22nd May 2012, 01:51 PM   #47
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Hi,

See attatched.
The copper foil is soldered to "pad" on the pcb, near I2S connector, and then being sticked to I2S wires + wrapping around wires.

The issue looks this way:
Click the image to open in full size.

On the board above, the "I/O" port goes as follows: GSSSSSSSSS where G is gound and S is signal. In general, you need at least one ground wire for each signal wire, and need to arrange them in "GSGSGSGSGSG"-style on the cable.

Connector should look like this:
SSSSSSSSSSS
GGGGGGGGGGG
OR
GSGSGSGSGSGSG



Your's B3's ports look better, in
SSSSSSSSSSS
GGGGGGGGGGG
style, but i'm not 100% sure the second row of each port is connected to ground. Check it out, and if they are connected to ground, use flat ribbon cables, and stick every 2nd wire into GND pad.
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File Type: gif EMC.GIF (8.8 KB, 623 views)
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Old 22nd May 2012, 04:46 PM   #48
PET-240 is offline PET-240  Australia
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Hey S3etup

Thanks for that, much clearer, picture paints a thousand pixels, probably more....

I am looking to use the u.fl connectors for the I2S to the BIII, thoughts on these? Will check the grounds as you advise, will see how I can fit the copper foil....

Thanks again,

Drew.
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Old 22nd May 2012, 05:45 PM   #49
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I've gone SMA myself, as these are crimpable, and easily obtainable connectors.
I do the I2S wires as described above, but these I2S wires go to the DFF reclocker on DAC's board, which gets it's clock from SMA. It's the cheapest way i could think of for maintaining best I2S signal's shape jitterwise - after reclocker.

u.fl are fine as long as you don't need to reconnect them several times (i've heard they would break). They should be much better than ribbon cables.
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Old 22nd May 2012, 05:53 PM   #50
qusp is offline qusp  Australia
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Quote:
Originally Posted by s3tup View Post
I've gone SMA myself, as these are crimpable, and easily obtainable connectors.
I do the I2S wires as described above, but these I2S wires go to the DFF reclocker on DAC's board, which gets it's clock from SMA. It's the cheapest way i could think of for maintaining best I2S signal's shape jitterwise - after reclocker.

u.fl are fine as long as you don't need to reconnect them several times (i've heard they would break). They should be much better than ribbon cables.
no actually u.fl are much hardier than people think if you handle then correctly and besides if you are doing lots of disconnect cycles for initial testing perhaps just use the ribbon (hardwired with minimal solder at dac end) for that and then use u.fl after youve confirmed correct operation, you should be planning your layout thoroughly beforehand anyway. pretty easy to replace anyway, particularly here when you are only using 1 x ring and the center.

but yeah as long as you dont try to just disconnect them by just pulling them off they'll actually last quite well. definitely either buy the disconnection tool, or fashion your own
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