The Vox Defiant Amplifier 1967 - 1972





Image of the Vox Defiant from the 1967 JMI Vox Catalog
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The Defiant was one of a series of five new Vox solid-state
guitar amplifiers introduced by Jennings Musical Instruments (JMI) in the summer of 1967. Other models in this series of guitar amps included the Supreme, Defiant, Virtuoso and Traveller. The new range also included three solid-state bass amplifiers; the Dynamic Bass, Foundation Bass and the Super Foundation Bass.

Modular Design - This new range of JMI Vox solid-state guitar amps incorporated a new modular design philosophy developed by Thomas Organ for Vox amp production in America.

Thomas developed a three-channel solid state preamp module in 1966 for guitar and a second modular two-channel solid-state preamp module for bass guitar. Thomas also designed three solid-state power amp modules rated at 30, 60 or 120 watt RMS. Thomas Organ used combinations of these five modules to create much of the US Vox amp line, including the Super Beatle, Royal Guardsman, Buckingham, Viscount, Westminster and Sovereign.

JMI experienced many problems with their early attempts at building a dependable solid-state amp. Their first solid state model, the Vox T.60, was introduced in 1962. It's 30 watt amplifier stage was powered by germanium output transistors that were
subject to repeated and costly failure, making JMI apprehensive to develop additional solid-state amp models. However, the success of the modular, solid-state Vox amps produced by Thomas Organ in 1966 proved to JMI that with proper engineering and by integrating silicon output transistors with large heat sinks, solid-state amps could be just as dependable as those with tubes.

With new found confidence and following the lead of Thomas Organ, JMI designed a two-channel modular solid-state preamp module in November 1966 that would be shared by four models of Vox guitar amplifiers. JMI also designed a similar two-channel modular preamp module for use in three models of bass guitar amps. JMI then designed four solid-state power amp modules rated at 15, 30, 50 and 100 watts RMS to be combined with these preamp modules, in turn creating seven new models of amps.

Printed Circuit Board Construction
Unlike the hand-wired solid-state T.60 amp and UL Series preamps that preceded them, the solid-state JMI Vox amps introduced in 1967 utilized printed circuit board construction.


Vox Defiant with a Swivel Trolley
The Vox Defiant
The Vox Defiant amplifier head was the union of the guitar preamp and 50 watt amp modules designed by JMI in November 1966. JMI intended it to replace the AC-50 MkIV. The preamp features and power output of the Defiant made it similar to the US made Vox Royal Guardsman. The matching Defiant speaker cabinet was equipped with two 12" Fane Speakers and one Goodmans Midax horn with crossover. The Defiant endured in the Vox line for six years, appearing in the 1967 - 68 Vox catalog, the 1969 Vox catalog, the 1970 Vox catalog and the 1971-72 Vox catalog.

Features and Effects
The Vox Defiant shared it's modular preamp and features with the Supreme, Conqueror and Virtuoso amplifiers. The features and effects of the JMI modular preamp and control section were virtually identical to those found in the modular preamp designed a year earlier by Vox in America.

The Vox Defiant control section had two channels, Normal and Brilliant. The Normal channel had two inputs, volume, bass, treble, tremolo depth and speed controls plus a "Top Boost" rocker switch. The Brilliant channel had two inputs, volume, bass, treble, a remotely footswitchable variable distortion effect plus MRB (mid-range boost) with a three-position frequency selector. A second three-position rotary selector allowed spring reverb to be assigned to either channel.

Control Panel
Unlike the costly anodized or etched and filled control panels included in earlier Vox amps, the two-sided control panel of the Vox Conqueror amp had simple white silk screened nomenclature on a black background, just like their Thomas Organ counterparts. The horizontal side of the control panel included all of the inputs, volume and tone controls. The effects controls (reverb, tremolo, three way MRB selector, distortion) plus the foot switch connector and pilot lamps were mounted on the vertical side of the panel. The placement of the reverb and distortion controls, three-position MRB selector, foot switch jack and pilot lights on the vertical side of the control panel varied over time for no obvious reason.

Three Button Footswitch
Originally designed by Vox for the UL Series guitar amplifiers, the cast aluminum three button foot switch shown at right was included with the Defiant amplifier. It provided remote operation of the tremolo, reverb, and distortion circuits. While many Defiants utilized the same six-pin DIN foot switch connectors installed on solid-state Vox amps built in America by Thomas Organ, some Defiants used a smaller five-pin foot switch connector. The Defiant head pictured above had the full size DIN connector.

Head Cabinet
In a break with traditional Vox cabinet design, the control panel faced forward rather than toward the rear. Head cabinets produced by JMI and VSEL (1967-69) were covered in traditional black basketweave vinyl, had front and rear panels covered in black Vox grill cloth, front and rear horizontal Vox name plates, gold cabinet piping, perforated steel grills, two-pin corners, pancake feet and a Vox logo handle. During the VSL era (1970-72), the Defiant head had a vinyl covered back, silver cabinet piping and plastic vent louvers.




Name Plates
The name plates on the earliest versions of the JMI Defiant amplifier were nearly identical to the horizontal and vertical logos designed by Thomas Organ for use on their US produced amps (see photo, far left). A "Defiant" model flag (shown at lower left) was installed on the lower right front corner of the head.

Later versions of the Defiant added the words "Solid State" to both the horizontal and vertical Vox name plates. The horizontal logo was also modified to have rounded corners.

Side Swivel Stands
Vox abandoned the traditional AC-30 Super Twin style swivel trolley in favor of a pair of swivel side stands for the Defiant and Conqueror speaker enclosures. The upper loop of these new side stands angled away from the enclosure to create a hand hold for transport. As the head would no longer rest on the trolley, JMI designed a set of restraining clips to secure the head to the speaker cabinet. This allowed the Defiant head and speaker cabinet to swivel together as a unit.

These side stands had a serious engineering flaw. The speaker enclosure, less the head, could be safely tilted as desired. However, once the head was secured to the speaker enclosure, the weight of the head shifted the center of gravity of the amp above the swivel point of the trolley. This created an unstable condition that could cause the Defiant enclosure to flip over backwards, slamming the amp head onto the floor. For this reason, most people removed the side swivel stands from their Defiant speaker cabinets.

The Hello Goodbye Video
More than fifty years later, a debate rages on regarding the three amps standing behind the Beatles at the Saville Theater for the Hello, Goodbye video. I'd like to offer my opinion about these amps.

Paul is standing in front of a UL series bass head. The UL Series amp heads had a row of controls at the bottom of the face plate, just as shown in the picture below and at left. All three speaker cabs have vertical "pie-shaped" Vox nameplates with white letters and traditional Vox trolleys. The combination of Vox logos with white letters and traditional swivel trolleys suggest that these are probably either UL730 or UL430 cabinets. Conqueror or Defiant cabs would have Vox logos with gold letters and swivel side stands.

It is really quite difficult to ascertain if the heads behind George and John are Conquerors or Defiants but the side stage photo of the Beatles at the Saville Theater offers the best clue. A side profile of the Defiant (lower) and Conqueror (upper) heads are shown at right. The photo reveals that a Vox Defiant head cabinet is deeper than it is tall while the height and depth of the Conqueror head cabinet are identical. The view from side stage suggests that the solid state amp heads behind George and John have the shallower profile of a Conqueror head.








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Photos and editorial content courtesy Gary Hahlbeck, North Coast Music


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