1967
The move to fully solid state Public Address amplifiers. Above, the PA50 in the JMI catalogue of April 1967. The PA100, depicted on the other side of the brochure's gutter, looks much the same. There are four microphone inputs, one music. The five channels apparently each have volume, treble and bass (volume above the socket); and there is overall volume, treble and bass at right. The amps in a sense bridge the gap between the all-valve MC amps (three mic inputs, one music), and the MC units with transistor preamps (five mics, one music). But the MC PA amps only have treble and bass controls for the master volume.
The knobs on the fascia of the amps pictured in the catalogue have numbered skirts and are probably the same as the ones used for the 7-series. Note that there are no legends for the controls though - only for the inputs and the "Master" at right. Nor has the indicator lamp underneath the master volume control been given any caption. ON/OFF and STANDBY switches will been on the rear panel (as in the solid state guitar and bass amps).
The two units as illustrated were presumably mock-ups for the catalogue. Quite how many were actually produced is hard to gauge - there are certainly entries for both in the pricelist of April 1967 - the PA50 at £105 12s 6d; and the PA100 at £134 - but none has ever been seen (or at least noticed).
Detail from the JMI pricelist of April 1967.
Their presence shows though that the move towards fully solid state PA amplifiers had begun at least a year before the new low-profile range - the PA50SS and PA100SS - was formulated. Below, details from JMI circuit diagram SSC/004, dated March 1968, for the PA50SS.
