The Catalinbread WIIO is a Hiwatt amp emulator specifically going for the sound of Pete Townsend’s Hiwatts on the Live at Leeds album. (Throwing this and a Univox SuperFuzz in the same box would be a must if you’re a big fan of the Who…) The topology of the circuit (cascaded MOSFETs) is similar to the zVex Box of Rock and Catalinbread’s other Hiwatt emulator, the Rah. Here’s the schematic for reference. Should fit in a 1590B just fine.
