DC Trigger Connection for Parasound 1205A

My pre-amp does not have a 12V DC source to trigger my 1205A amp, and obvioulsy I cannot use the pre-amps switched plugs since they are not sufficiently rated and only two prong. I did read a few forums on how to do this, however some options were expensive and I wanted to get some direct advice.

I do not clearly understanding how the trigger works; does it require a constant 12V source to keep the amp on, or only a 12V pulse?. Could a 12VDC/15mA AC adapter plugged into one of the pre-amp's switched plugs be safely connected to the DC Trigger? I'm trying to "wife-simplify" the user experience, which is an issue in itself...
Plug a 12vdc output wall wart into the switched outlet on your preamp, connect the other side to the amp's trigger input. Polarity likely won't matter since you're just energizing a relay, but double check that and the plug size / config with Parasound or your owner's manual.

You could also just leave your amp on all the time- it'll sound a little better if you do.
Thanks. Why does leaving the amp on make it sound better?