so are you pluging it into the dc power in on the AD-20? and not the 9v spot...
I amde a set up with a 12v Sealed Lead Acid Battery (12v 3.4 AmpHour PowerSonic PS-12130) to power my Denceke AD-20 and my (Phantom) PS-2
it could run both for nearly 20 hours
the ad 20 doesnt use much juice
but the Phantom, depending on the mics does...
I contacted denecke
I no longer use the AD 20
but was using the 12v SLA to power my Presonus Firebox
as far as I remember the AD-20 can be powered in a voltage range from 7v to 18 (maybe 24v)
I daont understand the noise issue though?
how does it introduce noise?
did this help?
or thats not the issue?