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Old 4th May 2013, 03:04 PM   #1
diyAudio Member
 
Join Date: Sep 2010
Location: Perth, Western Australia
Default Audio Pcb Layout Techniques

Hi All,
I've designed a few pcb's for myself in the last year or two, and as happy as I've been with the results, I really have no way of measuring success nor a framework to think about improving designs. As such I suspect I'm really fumbling around in the dark and there's improvements to be made on what I do. I'm completely self taught in this, so I've probably developed a few random methodologies that would do the be debunked.

In terms of learing it myself, iterating through 6 versions of the same idea to explore the differences isn't a practical option. So my basic question is

What are the fundamental ideas behind quality pcb design?

I could attach a few pcb layouts I've done as example pieces to discuss if anyone is willing to constructively critique the improvements possible (they are all single sided as I make em at home via toner transfer). So if this is helpful, please say so. I would imagine working through a few examples would benefit anyone wanting to learn this art.

To date, all I try and do are
1. minimize length/proximity of presumed current flows
2. minimize parallel traces/maximise orthogonal crossing of parts
3. er...

So, advice or links are appreciated. Thanks in advance.

Last edited by aspringv; 4th May 2013 at 04:09 PM. Reason: clarity, and I'm better the second time around...
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Old 7th May 2013, 04:10 AM   #2
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Location: Loxahatchee, Florida
asprinv.

It's late, and I want to do this topic justice, so I'll mull over it and write a long writeup, a paper so to speak, for you and whoever else is interested.

I am qualified to speak to this matter.

I am an electrical engineer, with a graduate degree in electromagnetics (the discipline most conducive to printed circuit board technology) over two decades of experience, and the top recognized subject matter expert in printed circuit board physics at my company, which is a multinational commercial, industrial, and military electronics giant. I have published multiple technical papers on noise, have developed a novel, proprietary PCB routing technique for integrating ultra-high speed baseband controller circuits into super-sensitive RF transceiver sets, I give lectures on the subject and teach classes on this topic at my company, and hold several US patents on PCB and noise-related technologies.

I am a PCB and circuit noise expert. (also the technical director of our multi-million dollar noise lab) I get "called in" and flown out to design centers around the world to fix PCB noise issues when entire teams cannot (in industry jargon, I am a "cleaner". Think Pulp Fiction. Cleaners clean up the scene of a crime (a broken design that's late for ship), remove the body, clear evidence, and make the crime scene disappear. "It never happened".). It's my bread and butter and I can definitely talk to this.

Give me a little while and I'll write something up that hopefully all can use. You'd be surprised at the little tricks that you can employ to reduce noise and crosstalk on a PCB.

So many experienced and seasoned folks here have helped me tremendously with speaker design concepts and the physics associated with them that I'd be happy, actually enthusiastic to "give back" for a change.

This is my element.

Last edited by Frankie Carbone; 7th May 2013 at 04:15 AM.
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Old 7th May 2013, 06:04 AM   #3
gootee is offline gootee  United States
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Frankie Carbone,

(It's very late. So this might not come out right. But I might not have time to get back here, soon-enough, so here goes...)

Wow. We have been hoping for someone like you for a long time. It sounds like it will be a great privelege, and of great benefit to us, to receive even just a few paragraphs, from you.

There are a few things that many people here very-often naturally get wrong, which I hope you will also touch on. One is unwittingly making what I would call magnetic antennas, or maybe they could be called "Faraday loops" (after Faraday's Law), by separating conductor pairs, often both the incoming AC Mains pair and transformer secondary wire pairs AND the input signal and input signal ground pairs. And having quiet and noisy grounds share conductors is another very common oversight, here. RF incursion is another mostly-overlooked area.

I am sort-of worrying that it might be a little difficult for you to translate your knowledge to our rudimentary available construction techniques, since you are probably very-accustomed to always having state-of-the-art construction available. The home-made toner transfer PCBs can almost-as-easily be made two-sided. So you can include that as a possibility. But it would also be extremely nice if you could somehow relate as much of your knowledge as possible to as many DIY construction types as possible, even if just in passing; e.g. no PCB, 1-sided home-made PCB, 2-sided home-made PCB, and, pro-made multi-layer PCB, which is much less common here, especially for one-offs.

(However, I am still also planning to try my "multi-layer" PCB "sandwiching" idea, at home, eventually. e.g. Design four or more 1mm or thinner pcbs (probably mostly 1-sided) that will be stacked tightly together at the end, with large-enough holes where needed in order to solder on inner layers, and etched-away areas for inner pass-throughs, etc etc. The benefits of having two power planes and a ground plane, and of thereby freeing up a fourth layer's layout to have only signal (and probably also ground), should make it well worth it, AND should also make the layout simple-enough that it won't be nearly as complicated as it might at first sound, especially for very simple circuits such as chipamp power amplifiers.).

Note that our typical home-made PCBs have no plated-through holes, and, any vias must be hand-made by soldering wires through pad holes. Among other things, that means that even with a two-sided PCB, we can't use a component-side connection to a large radial electrolytic, or under a terminal block, et al.

If you get fired up, you could probably become a huge hero simply by showing people here an example of, say, an ideal two-sided layout for an LM3886 chipamp. And there are certain very-widely-used PCB designs on this site for which any suggested changes might be of great benefit to many people.

Sorry if I have asked for too much, or "grabbed the wheel" too hard. I am just excited by the possibilities.

Regards,

Tom Gootee

Last edited by gootee; 7th May 2013 at 06:11 AM.
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Old 7th May 2013, 06:50 AM   #4
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Join Date: Feb 2012
Hello,

I too have to say, we all can be very lucky to have a person like you in the forum.
The thread's title immediately caught my attention, as I am a student in a sort-of technical high school (mechatronics dept.) and our electronics-lessons seriously lack a good education on pcb design. I started gathering that knowledge by myself, but somehow that's an impossible task without having someone to explain it.

I got a script about EMI scanned, which I received from one of my teachers, but there wasn't much interesting stuff in it. As an example, I couldn't find a single word on how to share quiet and noisy grounds and how to connect them.

If wanted, I'll upload it. Please keep in mind that it's written in german.

Best regards,
Daniel
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Old 7th May 2013, 09:45 AM   #5
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Join Date: Sep 2010
Location: Perth, Western Australia
Default Wow. That sounds exceptional. :)

Frankie Carbone - Thank you.

Sounds like you are indeed the one to speak to this topic. I (and I suspect many others) look forward to your contributions.

I'm very much in this hobby to learn and stretch my understanding and mind, so your proposed write up sounds like some excellent grist for mill! I'm looking forward to the journey.

Cheers,
Aren.
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Old 7th May 2013, 01:06 PM   #6
marce is offline marce  United Kingdom
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Some generic links covering a wide array of PCB related design notes and information.
One of the best books you can get is Henry Ott, "Electromagnetic Compatibility Engineering" a very good reference for may noise issues and EMC problems.
Attached Files
File Type: txt PCB related links.txt (5.1 KB, 213 views)
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Old 7th May 2013, 03:11 PM   #7
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Join Date: Sep 2010
Location: Perth, Western Australia
Marce - Thanks! I'll get cracking doing a bit of light reading then. Much appreciated for the links.

I'll chase up the book; again, thanks for the suggestion.

Edit - for those interested, a sample of the book can be found at https://play.google.com/store/books/...d=2-4WJKxzzigC

Last edited by aspringv; 7th May 2013 at 03:17 PM. Reason: linky
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Old 8th May 2013, 11:10 AM   #8
gootee is offline gootee  United States
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I bought that book a while back and it is great. And by the way, marce is also extremely knowledgable about PCB design.

You both should also do some searches for on line material by Henry W Ott as well as Bruce Archambeault, Howard Johnson, and Eric Bogatin.

Regarding sharing of conductors by quiet and noisy grounds: Simply avoid doing that. Use separate conductors for them, to connect to the star ground (asssuming you don't have planes). Otherwise, the voltages induced across the shared conductor's inductance (and resistance), by the noisy currents, or any dynamic (or large) current, will appear at the ground reference points that were supposed to be quiet, and will, for example, arithmetically sum with your amplifier input signal. Remember that even a small-amplitude current through an inductance can cause a relatively-large-amplitude voltage, if it is changing fast-enough.

Last edited by gootee; 8th May 2013 at 11:19 AM.
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Old 8th May 2013, 11:46 AM   #9
marce is offline marce  United Kingdom
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Bruce Archambeault

beTheSignal.com

Signal Consulting, Inc. - Dr. Howard Johnson

Speeding Edge consultants specialize in high-speed PCB and system design disciplines

And this book is a good gentle way of getting your head back into the physic's of signal transmission, often overlooked with conventional electronic convention, ie electrons whizzing everywhere, which they don't...
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Old 10th May 2013, 04:37 PM   #10
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Location: Perth, Western Australia
Default Looks like my university physics is going to get a workout!

Cheers all,
I appear to have a lot of reading ahead of me! Give me a few months and I'll get back to you all... <nose down in books>
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