[sdiy] PCB layout tips

[Tony Clark]

   Hi Scott,

> In AN-15 (Electronotes), BH suggests putting +ve and -ve supply lines 
> in two parallel rows underneath the chips. This sounds like a good 
> idea to me. Yet when I look at PCBs of various modules (from people 
> on this list no less), I never see this in practice. Is there some 
> reason why this is in fact a really bad thing to do?

   Well there have been some great technical aspects of PCB design spoken 
already, so I'll try to chime in with some of my two-bits worth...

   Putting the power lines between the chips makes for a rather _clean_ 
looking design.  But it _can_ cause problems depending on the trace 
density of your circuit board.  If you have many signal paths on your 
circuit board, having two large continuous traces running the length of 
your board can be a headache to route around.  (This may be only a 
problem for _ME_, however, as my trace densities are a bit insane!).
   Instead, I run the power lines on the outside, lowpass filter them, and 
then bring the dedicated line into the specific chip being powered.  That 
way each IC has it's own semi-isolated power line.  I find that to work 
the best for my circuit boards (again due largely to density issues).
   As for ground planes (or copper pours), I have never bothered to keep 
the traces seperated, although if you are mixing analog and digital 
stuff, you should definately have two grounds and separate copper pours 
for each.

   Really, for most synth stuff, it won't really matter a whole great 
deal HOW you route your boards.  Probably 99% of them will be fine even 
with the most chaotic of routing styles.
   In the end, everybody develops their own unique PCB layout style, so 
it's really up to you!  Try it and see how you like it!
  
   Cheers,

   Tony

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