[sdiy] split ground plane

[Joe Grisso]

I don't actually agree with what Achim says about
> connecting the ground planes at the DAC - I think they need to be connected
> so current to/from the digital stuff never flows past any analog parts
> (hence connect only back at the PSU).

Be very careful with this - some DACs and CODECs (especially from AKM)
use different design techniques for their power and grounding.
Depending on the design technique used for the IC, it may be sensitive
to deltas between the analog and digital power and ground planes.
AKM's layout notes (http://www.akm.com/AppsNotes/layout1.pdf) gives
more details for these. If you split the ground plane for a "delta
ground" device and induce more than 300mV of potential difference
between the planes, the device will either freeze or (I've had this
happen) latch up and fail. The same goes for a "delta supply" device,
except it's the power rail that has to have a minimal delta instead of
ground.

This definitely does not go for R-2Rs and older converters, but it's
something to take into account with more modern systems.

Best Regards,

-- 
Joe Grisso
Detachment 3 Engineering