Z1 MK1 Zonk Machine

Instead of germanium, the Z1 uses a matched set of new-old-stock Mullard/Philips BC108C silicon transistors, with a few components added to the original MK1 layout so the MK1 character holds at any ambient temperature.

Controls are Swell (volume), Attack (which works more like a bias control and adds crumbly decay past noon), and Sensitivity, which adjusts the crackling gate at the front of each note. A Zonk/Thick toggle switches between a bass-cut Zonk voice and a fuller MK1 tone. The circuit is built on a brown phenolic board with Alpha pots, JB capacitors and Lumberg jacks, and is powered from a 2.1 mm centre-negative DC jack with no battery snap.