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ron.eddy 18th December 2005 01:19 AM

Amplifier PCB Layout Guidelines?
 
I was attempting to make a few circuit boards in Eagle the other day and after spending hours and hours trying to make the components fit while keeping signals in order I gave up. I did eventually make a "complete" layout for the circuit I was working on (See pics below) but I am not sure it is a good way to go. It is just a simple circuit for a Randy Slone headphone amp and I just wanted to practice laying out components using it. But I just am not happy with it at all. It seems like it got put together only through luck, and not skill at all! :) :) :)

So my question is: Are there any general guidelines you pros could give a newbie like me in laying out a circuit, especially when it has multiple pin devices in it such as ICs or chip amp transistors like the LM3886? I mean, with what components should I start? What are some things to keep in mind as far as certain signals being next to certain components? Etc. From what I gather all this comes with experience, but I would like to speed that up a bit, since experience could take a while (I never was all that patient :D ).

Any tips would help a great deal, I just don't have a very creative brain as far as improvising things like layouts, so any kind of structure to this process will help me and any other like minded DIYer out there.

Thanks!

- Ron

http://people.aero.und.edu/~reddy/circuit-sm.jpg

http://people.aero.und.edu/~reddy/layout-sm.jpg

Leolabs 18th December 2005 01:25 AM

try to search on the forum,with the term"circuit board design".

ron.eddy 18th December 2005 01:40 AM

Searching this forum didn't yield very many direct responses to this sort of question, but going into each project and reading the tips on those specific circuits does help. Thanks for the advice. I just wish there was a more centralized place to learn.

I should note that I have already read the PCB design guide here and am actually asking in this forum for any little tips or advice you all could give for audio specific circuits, as I said especially when IC's/multiple pin chips are involved.

Ron

poobah 18th December 2005 01:44 AM

Looks fine dude ... and it ain't easy... takes lot of practice to do it fast.

If Eagle lets you do 45's, replace all those 90 deg turns with 2 45's.

If you want it smaller... that just takes work and patience.

As far as the "black magic" is concerned. just keep your outputs away from your inputs... audio is pretty forgiving as far PCB's go.

:D

poobah 18th December 2005 01:47 AM

Is this going to be a single or double sided board???? LOOKS like single...

ron.eddy 18th December 2005 02:12 AM

Yes, it is a single side, however there is one component on the top side (the 1206 SMT capacitor) but that will actually be going on the bottom side, I just couldn't figure out how to make eagle put it down there so I just left it as is, figuring if I ever made the board I can make it go on the bottom, real close to the two pins it is connected to.

Anyway, what you say about audio circuits is exactly what I thought too (I figured at these low frequencies there shouldn't be anything to worry about) but I think some may disagree on this forum about the audio being pretty forgiving. In fact, this is what most of my confusion rises from. When I go to look at other's projects on this forum and they ask for advice on their PCB layout, usually they get a TON of responses telling them to keep signal A away from those caps, or make sure those traces are short or whatnot. So seeing all of that frustrates me, since I know there are so many suggestions out there and it isn't possible to remember them all.

In any case, I guess a good question I could ask is, how long does it take one of you more experienced DIYers to layout a simple circuit such as the one I have done? This one took me 14 hours and I just never could get into any sort of rhyme or rythm with it.

Mike Gergen 18th December 2005 02:27 AM

Practice, practice, practice.

poobah 18th December 2005 02:28 AM

Check you email - :D

mzzj 18th December 2005 02:37 AM

Quote:

Originally posted by ron.eddy

Anyway, what you say about audio circuits is exactly what I thought too (I figured at these low frequencies there shouldn't be anything to worry about) but I think some may disagree on this forum about the audio being pretty forgiving.

It depends where you compare it. :)
Try fitting SMPS and a mic preamp on same board if you like challenges :D

Where you are going to connect those bypass cap gounds together? AD797 is usually tought as tricky nut to bypass compared to any other audio-opamp. Aim to keep total trace+component lenght minimal between supply pins, bypass caps and ground.

I usually start with bypass cap placement, then feedback resistors and after that rest of the stuff where it fits. Dont be shamed to use jump wires on 1-side board, its way more better to use couple of jumps than run signals around the board in loops trying to not use jumper wires. Some people seem to rate pcb layout by amount of jumpers used, thinking that less is better.

ron.eddy 18th December 2005 02:37 AM

Quote:

Originally posted by Mike Gergen
Practice, practice, practice.
Yea, good plan. It is fun, in an odd sort of way.


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