JMI Vox Wah c. 1967	Click images to enlarge
Possibly not as rare as most people believe, here are three of the sought after grey Vox wahs. Often mistakenly referred to as prototypes, they were in production for some months, possibly into 1968. It is true that they were based on the prototype circuit sent to JMI from Thomas Organ, but nevertheless it's clear they were considered a production model by JMI. Cardboard shipping boxes were printed with the same WAH-WAH graphic and the pedal was advertised in the music press (see scan at the bottom of this page).
The grey Vox wah housings are slightly larger than the Italian and US versions. The throw on the treadle is about 1/2" longer on the grey wah.
Input is on the left, output on the right, like the early Tone Benders and Fuzz Faces. Some have a hardwired cable instead of an output jack.
Vox lettering is raised, unlike the Italian pedals. The castings were linished roughly and brush painted with silver grey Hammerite.
The serial number is stamped into the bottom plate near the front edge. The known range of serial numbers covers around 2000 units.
In an interview published in Guitarist magazine, Dick Denney claimed he and his wife assembled and wired these wahs at their home. Note the DPDT switch wired for true bypass.
The circuits in early examples were covered in black epoxy in an attempt to prevent them being copied. According to the JMI factory circuit diagram, the inductors were nominally 250mH, although they vary considerably. The lower inductance results in a much higher sweep range than most wahs.
TI 2N3707 transistor, dated 16th week of 1967. The factory circuit diagram shows BC150s, which were used in the early units.
Magazine ad from 1967. The grey Vox is most associated with Jimmy Page, and can be heard on the late Yardbirds recordings and the first two Led Zeppelin albums. Other artists using these wahs included The Beatles (on Across the Universe) and, taking an educated guess from the sound on the recordings, Pink Floyd (Apples and oranges), Status Quo (Pictures of Matchstick Men) and the Pretty Things (Bracelets of Fingers). Thanks to Philip for the scan.