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Old 10th August 2012, 02:33 AM   #1
diyAudio Member
Join Date: Aug 2012
Default Where to get started?

I am interested in learning more about PCB design and how it relates to audio etc, but there is so much, it seems difficult to find a place to start.

I understand logic gates, flip flops, registers, adding/subtracting/logic operations on registers, processor cycles, timing signals, and microinstructions through my computer architecture class, but I am more interested in how to start designing electrical devices that utilize these from scratch

Maybe there are some good projects to get started with?
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Old 11th August 2012, 06:28 PM   #2
marce is offline marce  United Kingdom
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Join Date: Jun 2007
Location: Blackburn, Lancs
PCB design is related to electronics, and audio repreduction involves electronics. Depending on what is being designed audio can encompass digital, analogue, power layout techniques. Learn and master these layout requirements and you can lay out PCB's for audio. The attached text file has a few links that show some of the stuff yoiu need to understand for PCB design.
Attached Files
File Type: txt PCBlinks.txt (5.1 KB, 10 views)
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Old 11th August 2012, 10:52 PM   #3
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Join Date: Jun 2011
You're right, it is difficult.

Difficult but not impossible.

It helps that you understand logic circuits, but logic circuits have just high or low values, analog design is a whole new subject.

Stick with the logic design, it contributes to having confidence that you can make circuits that work.

It's easiest if you have someone to teach you, so getting on a course helps. Radio amateur societies often run courses for those interested in getting a license, although these naturally have a bias toward radio.

A brief list of subjects required includes simple 'light-bulb' circuits leading to an appreciation of resistance, voltage and current and expands through Kirchoff's laws to Norton's and Thevenin's theorems followed by electro-magnetics and capacitance.

A special area requiring attention is operational amplifiers.

Some exposure to logarithms (dB), trigonometry, Fourier analysis, real and apparent power and complex numbers helps.

Semiconductors (diodes, transistors), thermionic valves, noise and feedback must also be dealt with along with AC and DC, transformers, rectification and power supplies.

You can look up any of these subjects on google and try to make sense of them.

The Radio Amateur's Handbook from the ARRL or the Radio Communications Handbook from the RSGB both contain sections on basic electronics which are updated yearly.

A book on practical design for more advanced students is The Art of Electronics by Paul Horowitz and Winfield Hill. It has very good sections introducing the design of single transistor stages and also deals with power supplies and some digital issues.

A project for someone with some grasp of digital design might be the design of a digital (microprocessor controlled) volume control, with buttons for up and down and a (7-segment?) display showing the set level. You could follow this with an opamp or other simple stage to drive headphones. You'd need access to a programmer, but a USB programmer for PIC can be had on ebay for very little.
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Old 11th August 2012, 11:36 PM   #4
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Join Date: Feb 2009
Location: UK
I think you can also take the view that it's very easy...

Most circuits will just about work when built on Veroboard, so it's quite difficult to make a circuit that won't actually 'work' better when built on a PCB. If the actual cost of the PCB is not a major factor, then a four layer board (with more-or-less solid ground and power planes on the inner layers) eases the task considerably.

Understanding the typical PCB design package and its 'workflow' is the first thing, though. There's a lot of jargon and terminology to understand (most of it pretty straightforward once you look it up and see an example of it), and a few technical and file format-related pitfalls you might fall into when sending off your first PCBs for manufacture. Once you've got all that stuff under your belt, you can start to consider the finer points - which are more often rules of thumb and common sense than rocket science. The major area of debate is grounding, and you'll see all sorts of recommendations regarding the separation of analogue and digital grounds, particularly in digital audio. My tip for the top when starting out in all this, is to follow the advice given to me by a real hard core physics/maths/electronics expert many years ago: use a 4 layer board and simply stick to a single solid ground plane for everything, and you won't go far wrong.

(By the way, don't dismiss Veroboard out of hand as a method for constructing high performance prototype circuits. The key is to completely cover the top layer with self-adhesive copper tape which forms your ground plane. You solder any component leg that requires grounding directly to it, and cut small holes with a scalpel to pass any other component legs through. It's a lot quicker and easier to do than it sounds, and it eases your layout problems considerably).
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Old 12th August 2012, 08:17 AM   #5
marce is offline marce  United Kingdom
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Join Date: Jun 2007
Location: Blackburn, Lancs
I'll second the ground and power plane. I never do 2 sided boards these days and havn't for many years. With digital these days they are almost mandatory due to even the most simple design being high speed, the speed of a circuit is determined by the signal rise time not ultimate clock frequency. The links I have posted above have several guides on analogue digital layout, the main thing here is seperating the analogue and digital sections as much as possible.
The hardest circuits to lay out are realy high speed digital, RF and SMPS's.
Also look up RS-274X (Gerber) Excellon (drill data) and ODB++ you will have to understand these formats to transfer you data to a PCB manufacturer (ODB++ is best).
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Old 12th August 2012, 03:44 PM   #6
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Originally Posted by gingerkid101 View Post
I am interested in learning more about PCB design and how it relates to audio etc, but there is so much, it seems difficult to find a place to start.

Maybe there are some good projects to get started with?
Your starting project should be something that interests you and only you can answer that. But, since you asked, I suggest a discreet, R-2R DAC. That will give you a mixture of analog and digital. You can make is as simple or complex as you wish. I also think it would be more interesting than the usual CS8414/TDA1543 DAC that's been done a million times already.

As for PCB design, www.expresspcb.com offers free schematic capture and PCB layout software for use with their PCB-manufacturing service. Compared to the pro level programs, the software provided has fewer features but it is easy to learn and use. If you can live the limitations, you can get three, small, two-layer PCBs made for as little as $51; four-layer for $98. Larger and more complex boards cost more.

Iíve been using them for years. (I have my own CDL integrated with the ExpressPCB layout software.) Each time I think I might benefit from a full-featured PCB layout program and a full-featured PCB manufacturer, I look at the learning curve required and the additional expense. In all the cases I have examined it was not worth it.
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Old 13th August 2012, 11:04 AM   #7
marce is offline marce  United Kingdom
diyAudio Member
Join Date: Jun 2007
Location: Blackburn, Lancs
For the majority of DIY stuff the free programs will suffice. Express are a capable PCB manufacturer and the service they offer is excellent for small runs DIY.The difference between what you can do on basic software and a full blown package is not that great for basic designs (4 layer layout, simple logic etc), it when you get on to PC motherboards, FPGA's etc hat the features of a full blown package with simulation, 3D transfer etc etc comeinto play, and even then for the majority of designs (apart from the number of layers) the main features you use are the basic ones. Placing components is the critical part of any layout mastering that is the main skill that you can develop for PCB design, this means you have to look at the pattern of ats nests (the connections) and picture how they will route depending on your placement.
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