If you leave the power switch on, yes, the batteries drain.
You will get roughly 100 hours from each set, so leaving the preamp on for an hour will deplete 1.0% of the life of that set of batteries (D-cells and 9V's).
-PB
« Last Edit: February 17, 2014, 06:20:52 PM by Caucasian Blackplate »
Paul "PB" Birkeland
Bottlehead Grunt & The Repro Man