Double sided ground plane?

[chromesphere]

Hey guys,

Cant google a straight answer on this one, suspect the answer will be "for most anything pedal related, its probably not going to matter" but thought i would check anyway.

On a 2 sided board, is it best to have only one side ground planed?  Also, should one side generally be dedicated to ground?  Does it matter if both sides are ground planed?

Any advise appreciated!

Paul

[R.G.]

Ground plane is one of those special-purpose tools. It can help, it can hurt. Depends on what the signals and impedances are.

Ground plane is almost requires for signals from low RF on up. It does no special good for audio and below other than putting a lot of copper there. That might help if there is a lot of ground current, and it may help if you have unusual capacitive coupling situations. At DC and audio, you are often concerned with exactly where a current flows. Ground plane makes this almost impossible to manage. You have to just try it and hope. Often it's not a detriment. ICs which have a tendency to oscillate if their power supply has high or inductive impedance (or both!) or which have frequency responses up into the RF and which are not properly decoupled with local decoupling caps may get advantages from it, but again this is its high frequency goodness that's helping.

Things on pedal boards with digital logic and regular clocks may need ground planes for the high frequency reasons.

So -
(1) Do you need one ground plane?
Maybe. If you have digital logic, very high performance transistors, FETs, and so on with high frequency responses, or sloppy power and ground routing and decoupling.
(2) Do you need two ground planes?
Maybe. This makes it very difficult to reverse engineer something for beginner reverse-engineerlings. For audio stuff, I'd call this it's primary virtue.

Note that one ground plane makes repair work more difficult on anything with a grounded lead, and it makes mods tremendously more difficult. If any of these matter to you.

For my personal work, I can have as many ground planes as I want, just by doing what amounts to telling the machine: "Ground-Plane, Go". This takes a second or two to run. I do not put ground planes on all-analog stuff, I put ground planes on mixed analog and digital, and have never felt the need for two-sided ground planes on two sided boards for effects work.

I have done four and six plane boards for pure digital logic.

It's like castor oil - take only the amount you really, really need.   

[chromesphere]

Very informative RG, thanks for hte detailed response!  I'm going to get rid of the 2nd ground plane, i dont think its necessary.  The particular board im working on at the moment is a modified punch amp (tda7052a 1 watt chip amp), fabricated.  I have decoupling at the plus and minus of 100uf.
Paul