This page picks up from the general overview of Vox microphone mixer units, 1964-1968. Evidently the first batches of mixers supplied by JMI to Thomas Organ were Mark 2s - probably part of the second major shipment to the USA in early 1965 rather than in the first (of September 1964). Mark 2 mixers - variously designated the "M2", "M.2", and "M.II" - had three low gain inputs, three high gain, and overall treble and bass controls. Cases, made for JMI by P.A. Glock in Crayford, were of wood with a vinyl covering, the front attached with latches.

In April 1965, Thomas priced the mixers - product code "V-7-2" - at $150.00. This was nearly two times more than the JMI list price in the UK (£28 and 7 shillings), packing and shipping doubtless accounting for a good proportion.

A facsimile detail of the Thomas pricelist "effective April 1965". This will be replaced by a photo of the original shortly.

Below, a detail of the illustration in the "King of the Beat" catalogue:

Six channels, high gain inputs at left, then three low gain. At right overall Bass and Treble controls. The front of the cabinet, with its storage compartment, could be completely removed.

Few Mark 2 mixers are seen these days in the USA - or in the UK for that matter. Currently (Jan. 2023) only two are known, many originals doubtless having been scavenged over the years for their germanium transistors, pots, and so on, and the rest discarded. Mark 3 "metal-clads" are by far the most common type.

The Mark 3 (M3, M.3, M.III)

One of the most variable aspects of the Mark 3 was the type of transistor used. One very often finds RCA 2N2613, but not always. The JMI circuit diagram (OS/082), dated June 1965, envisages the OC71 and AC107. Production clearly moved in stages, perhaps in line with the price and availability of certain classes of component.

A detail of Mark 3 serial number 340 (or 349), exported to the USA early on, probably soon after production. The visible transistors are OC44s.

The back panel with stencilled owner's name and address.

In the sheets pictured below, Thomas envisaged germanium SK3004 and SK3003/SK3005, presumably made by RCA, and good equivalents. Lists of "transistor equivalents and substitutes" published in the 1970s certainly give the SK3004 as an alternative to the OC71, and the SK3005 as an alternative to the AC107.

On a point of detail, C1 and C12 in English-made units are normally 5uf, not 2uf. Whether 2uf is reflected in the build of mixers that found their way to the USA is not clear at present.