Analogue-sequencer

> Id like the polydac hardwired to the p3, but my own machine 
> is prior to you adding multiple midi outs - I assume youd 
> recommend me 
> cloning whatever circuitry you used on the latter p3s on a 
> bit of stripboard or something, to replicate the existing 
> single midi out 
> for the polydac's input?

A MIDI connection is optically isolated to prevent ground loops.
If you are connecting two devices that already share the same ground
internally, you can just wire the UART TX pin on one CPU to the RX pin on
the other, and save an unnecessary opto-isolator.
 
> The polydac installation would take preference over battery 
> power and i havent looked into polydac battery operation at all yet, 
> but, with regards to the p3, im assuming simply feeding the 
> power from the batteries in post regulator would do the 
> trick, without 
> any other issues?

As long as the battery voltage stays within spec for all the ICs, you might
be OK.
Personally I think I would use a high efficiency DC-DC convertor to convert
whatever the battery voltage might be to an accurate 5v.
That will give you maximum operational reliability and battery life.
A multi-output convertor could give you the necessary rails for a polydac
too.

Best regards,
Colin Fraser
Sequentix Music Systems Ltd
http://www.sequentix.com