Test circuit before reinstalling back cover. I tested the 1/4" jack with a guitar, and the 3.5mm jack with an audio interface.

The amp drew about 0.025A, or 25mA when listening to music through the 3.5mm jack.

With a guitar plugged in, anywhere from 0.025A (no sound) to 0.075A (practice volumes) were witnessed. For those wondering, a timid strum with the knobs set to full resulted in a reading above 0.105A!