Phil Allison wrote:
"Eiron"
Assuming that inside the DAC is a bridge rectifier, a big capacitor, and
a regulator, it should be just as happy with a DC input as with 12v AC.

** Very bad assumption.

The main reason makers use AC output adaptors instead of DC ones is to
generate MORE than one DC voltage rail inside the device.

Two diodes and two filter caps gives +/- 18 volts DC from 12 volts AC.

More diodes and more caps can increase the number of rails even further.

Won't work with DC - see:

http://hyperphysics.phy-astr.gsu.edu...c/voldoub.html

That's all very well and I'm sure you often teach your grandmother to
suck eggs
but we are considering what's inside this box:
http://www.cambridgeaudio.com/summary.php?PID=320

--
Eiron.