The Vox MC50
50 watt Public Address amplifier
The MC50/4 in a well-thumbed copy of the JMI newspaper format catalogue "Precision in Sound", late autumn 1964.
The "MC" of the model name stands for "metal clad". MC50s (sometimes called the PA50) were produced for Vox under contract by Triumph Electronics in Purley along with the other models in the range - the MC15, MC30 and MC100. Triumph also produced AC50s for guitar and bass through to early 1965.
The earliest units, ie. those illustrated below, were all valve, four input, and had plain metal cases with sloping fronts. Bulgin chicken-head knobs were fitted to the control pots. Initially all models had four channels: - three for microphone and one for music. Each had its own volume. Overall treble and bass could be varied via the controls on the upper right hand side of the fascia.
During the course of 1964 JMI developed two new units - the MC50/6 and MC100/6 - flat-fronted, transistor preamp with six inputs, meter on the front (so that bias voltage and power output could be read), and a valve power amp. In other words these were hybrids. They were exhibited for the first time at the Russell Hotel Trade Fair, August '64.
Certainly where the MC100/4 is concerned, sloping front became flat front in mid 1965, though all else remained the same. AC50/4s were presumably issued in the same way.
Towards the end of 1965 a new format was introduced: - amps with dark blue-grey fascias (both MC50/4 and MC50/6) and silver lettering. Examples can be seen on this page.
The power sections of the surviving units below are all solid state rectified. But it may be that the earliest units had valve rectification. It seems likely that the smaller metal-clad amps - the MC15 and MC30 - were valve rectified through to the end of 1965. No circuit diagrams for the range have so far come to light however.
Serial numbers of the PA amplifiers ran as part of the same series as the guitar/bass amps.
Although reasonably large numbers were produced, survivals are fairly few and far between, as is the case with most early public address amplifiers. Many are likely to have been gutted for parts or junked in the 1970s and 1980s.
References to PA units in music paper small ads are being collected together here.
1964
First generation Metal-Clad amplifiers
A page from the catalogue of 1964, put to press in February 1964. Note that the units as described (though not depicted) have "two low impedance inputs" and a "master volume". Envisaged use: "For factory, theatre, club, pop groups, etc.".
A detail from the "Precision in Sound" newspaper of 1964. The units pictured above have "three high impedance inputs and one music input" The surviving amplifiers below follow the format depicted.
1965
Second generation Metal-Clad amplifiers
Updated, Jan. 2025
Vox MC50 (Metal Clad 50) serial number 2666
In superb condition. One of the blue Hunts capacitors in the power section has the date code "TDT"" = 48th week of 1964. The amplifier is likely to have been assembled at some point towards the end of the first third of 1965. Thanks to Christian for correcting the serial number, wrongly given initially as 2885. The amp is still in fine working order.
Vox MC50 serial number 3901
Sloping front, solid state rectified, assembled by Triumph Electronics for Vox in early 1965. Serial numbers ran in the same sequence as those assigned to AC50 guitar and bass amplifiers. Judging by small ads placed in music papers of the later 60s and early 70s, Triumph made reasonably large quantities of these Public Address units. They are scarce today however. Thanks to Daniel for the pictures.
Note the all valve preamp and power amp. Triumph also produced hybrid Public Address amplifiers for Vox - transistor preamp and valve power amp - long before the company embarked on making the 7-series range.
Vox MC50 serial number unknown
Sold on ebay some time ago. Well used, but all important components still in place.
On to the page on Vox PA50s, 1966 to 1968.