You can plug in your headset to the test jack on the P5 and listen to the audio inputs into the CVR anytime a.c. power is on.
Now I dont have our schematics in front of me but the inputs are active without oil pressure.Is it recording though?
The 115vac answer sounds best to me.There are a few nasty configs I can think of where you have no oil pressure but still flying.It would be handy to hear what was going on in the cockpit under those conditions.
Someone will have the schematics available for definitive answer.