The Custom Mach II was the first deviation from the Wal production line. It features a slightly larger body than the Pro with an elongated upper horn for improved balance specifically designed for this, their first, five-string model.
It has a pair of custom designed Wal humbucking pickups, new bridge and headstock designs and a two-octave fingerboard. The on board active electronics were sophisticated for the time and, more importantly, highly reliable.
The tone controls are actually low pass filters and when the controls are pulled up you get a boost to the harmonic frequencies. The Volume control also has a pull switch function to introduce a high frequency element termed pick attack.
The battery is housed within the control cavity along with the circuit boards and there are trim pots for all but the balance control. There's enough adjustment available here to significantly alter the sound of the bass giving many Wal basses their own distinctive qualities. Session players love the DI socket but a jack plug still needs to be inserted in order to switch on the preamp.
As with many relatively small manufacturers, dates and material spec is hard to verify as records are sparse and many Wal basses were made to customer's requirements, hence Custom in the title. Paduak and hornbeam necks were often requested and quilted maple or American Black Walnut facings were very popular in the eighties. Fretless versions usually had ebony boards. The Mach II has also become known as the Mark II and this new design proved so popular that a four-string version soon followed.