Its got a triordial (spelling?) transformer... that pp2+.
If you put your wah pedal too close to it, it will hum... but... take your dirt pedals, a sensitive one like one with transistors, and... the hum's very minimal, if any, and there's hum only at certain spots... e.g. on TOP of the PP2+, little to none at the sides.
If you put your wah pedal too close to it, it will hum... but... take your dirt pedals, a sensitive one like one with transistors, and... the hum's very minimal, if any, and there's hum only at certain spots... e.g. on TOP of the PP2+, little to none at the sides.