Vox PA units

In 1965 The Who evidently used a first generation 100 watter - one of the sloping-fronted "metal clads":

On the left, the PA amp behind John Entwistle.
On the right, a page from the 1965 Vox catalogue (repeated from the page on 50W PA amps).

Dick Denney at the Russell Hotel Music Fair in November 1964, with a 50W or 100W six-input PA to his left.

Surviving examples of early 100W Vox public address amplifiers are yet to come to light, but it is to be hoped that some do still exist.

Vox PA units

In 1966 Triumph Electronics put into production for Vox a new set of 50W and 100W public address amplifiers, some with transistor preamps, though the power sections remained all valve. The blue/grey and white livery was applied also to the growing array of Vox Effects Units, and other devices:.

Above, the Vox Guitar Organ power unit

The catalogue in which the range appears is available on the Vox Showroom website.

In terms of electronics, a notable feature of the new 100W PA amps is the provision of individual bias controls for the output valves, similar to those of the Vox UL 4120 and UL 7120, also assembled (and designed) by Triumph.

Vox PA units

PA100 type 2 - transistor preamp, meter on front, two speaker outlets

Serial number unknown - currently in the UK

Currently in the UK, an extremely rare PA 100 with power meter. The transistor preamp looks good and intact; the power section does require a little attention though. Two of the four EL34s were replaced at some point by 6L6s.

June 2013 - the amp now beautifully restored and in full working order. Thanks to Mick for the pictures.

PA100 type 3 - transistor preamp, meter on front, four speaker outlets

Serial number unknown - currently in the UK

Sold on ebay in September 2014. Box and power meter missing, but great condition. Assembled by Vox for Triumph Electronics. The preamp, as above and below, is solid state. Power section is all valve with individual bias controls for the EL34s.

One of the pots has the code "AO" = January 1967.

The same amp as above, cleaned up and with the addition of a power meter.

Serial number unknown - currently in the UK

Sold on ebay.uk in early 2014. Just the power amp chassis, but in good condition. This is a larger (wider) unit, as above, with four 1/4" jack outputs rather than paired round Bulgins.

PA100 type 4 - valve preamp and power amp, redesigned box, two outputs

On the left, the band Styler's Musical Express playing at the Lion Hotel, Singapore - note on the centre of the riser a metal-clad PA much as the 100 watter below. Centre and right, the Yardbirds, April 13th, 1967.

Serial number unknown - currently in the UK

A 1966/67 monster in good physical and cosmetic condition. Many elements are similar to the 7-series amps - tagboards with eyelets (instead of hooks), Mustard capacitors, insulated stand-offs on the chassis, and individual controls for the output valves' bias on the back panel. The EL34s are the original ones, with Mullard date codes B5G2 = Blackburn Factory, 1965, 2nd week July.

Vox PA units

Later, it seems that there was a plan to replace these amps with a new all solid state version, as part of the line of all solid state guitar amps (the Conqueror, Defiant, Supreme, and so on):

Image from a brochure reproduced by J. Elyea, Vox Amplifiers. The JMI Years, p. 485. See also the Vox Showroom catalogue section - first page - second page.

No surviving examples have hitherto been seen however.