[sdiy] PCB GND planes layout advices needed...

[Jean-Pierre Desrochers]

I need your advice on the following:
I just completed the PCB layout of my new polyphonic (6 voices) MIDI2CV dotcom type module.
It's a 7" X 8" 2 layers PCB. 
I'm using a power connector with the following specs:

Molex 0.156" spacing
Pin#     name
1         -15VDC
2         ANALOG GND
3         ANALOG GND
4         +15VDC
5         DIGITAL GND
6         +5VDC

Both ANALOG & DIGITAL GND's are wired  separately until they reach
the remote power supply using different wire paths.
There (and only there), they are wired together.

The board includes analog IC's (opamps, DAC's, transistors, etc..)
and digital IC's (PIC microcontroller, gates, opto, etc..)
Now that my OrCAD soft has helped me place
both layer traces and since the ANALOG & DIGITAL grounds are 2 separate nets,
I'm doing a 'copper pour' on the TOP side with
the ANALOG GND net and a 'copper pour' on the BOTTOM side using the DIGITAL GND net.
That's what are normally called GND planes..
I know the actual TOP layer ANALOG GND generated plane will
help a lot getting rid of noise all around the board, my question is:

Is it a good idea to generate a DIGITAL GND plane on the BOTTOM side too
or leave the DIGITAL GND paths not covering most of the BOT surface???
(Remember ANALOG & DIGITAL GND'S are NOT wired together on the board)

Thanks
JP