List of updates / new info. on Vox solid state amps (1967-1972)

2026

10th July

Thanks to Björn, a couple of shots of VSL Supreme serial number 2544, probably later 1972, .

7th July

A couple more decapitated Virtuosos, the second fairly skilfully done as these things go. Five in total are currently known.

6th July

Thanks to Mark, details of Vox PA50SS serial number 1151 from later 1969 .

4th July

As mentioned in yesterday's entry, pre-production solid state amps were fitted out by JMI with American-made Amphenol mains sockets - an unusual choice. Standard production amps, starting from November 1966, had English-made Belling Lees. Below, a detail from the Burndept components sheet for the Supreme and Super Foundation Bass.

A Belling Lee L1722/S in place.

3rd July

Photographs of the solid state amplifiers submitted by JMI to the Patent Office on 27th July 1966. Seven survive: four for a Defiant/Supreme amplifier section, three for a Foundation/Super Foundation Bass. Legends and logo, which formed no part of the submission, were struck through in blue. The pictures will naturally have been taken earlier in July.

Design was already well advanced. The control panels of the two versions (bass and treble) were on printed sheets of some sort though - i.e. designed but not printed on metal. Although it is not known for certain at present whether solid state bass amps were displayed at the London Trade Fair in late August 1966 along with the Conqueror and Supreme, the pictures below do suggest so.

One of the (many) peculiar things about the pre-production amps is the presence of an American Amphenol mains sockets of a type not used before by JMI. Plugs to fit will have been extremely uncommon in electrical shops in the UK in the 1960s. Stock was presumably available to JMI via the Amphenol factory down the coast at Whitstable.

Was the intention originally to release the range to coincide with the Thomas amplifiers (shown for the first time in late June / early July 1966)? A few months later the two companies certainly synchronised their advertising and release of the Wah-Wah pedal.

Detail of the Amphenol socket.

Amphenol socket on a pre-production Defiant. It is extremely hard these days to find plugs to match. The US standard changed at some point in the 1980s. Later plugs that at first glance look the same do not fit.

2nd July

There is now a page on the .

1st July

A synopsis of sections D, E, and F of the Warwick Industries report of Dick Denney's visit to Sepulveda in October 1965 published in "The Vox Story", ed. Denney and Petersen (1993), pp. 141-145. Copies of "The Vox Story" are still relatively easy to come by - well worth buying or borrowing.

1: - three transistor amplifiers are expressly mentioned: "engineering protoypes" of proposed 30W and 100W models, the latter already termed the "Super Beatle"; and a production example of the "Essex Bass".

2: - the 30W and 100W prototypes evidently had at least two channels - Normal and Brilliant - perhaps Bass too though nothing is said explicitly. Denney is reported as having found the tremolo (on the Normal Channel) "very good".

4: - the 100W version was tested with a bass guitar, and an unpleasant sound noted at volume. During Denney's visit, a limiting circuit (an existing but unused Thomas design) was added.

5: - no explicit mention is made either of reverb or distortion.

6: - Denney is said to have approved of the modular design of the proposed range - front end the same, but varying power chassis of different outputs.

7: - following discussion, it was felt that the Essex Bass might benefit from the limiter too.

8: - the Essex Bass had the Tone-X circuit (which Sava Jacobsen later indicated was of his own design).

9: - the paragraph on the tone circuits of the 30W and 100W engineering prototypes begins with a sentence noting that they were judged to be "satisfactory". Some of the statements that follow are a little difficult to construe in places though. It may be that a number of the elements presented for assessment were on independent boards (separate assemblies) that could be connected and disconnected for testing and review. The report states:

"The resonant boost feature may represent a new sound in guitar amplifiers and can be carried to any degree of variety by providing multiple switch positions. Warwick proposes, at this time, to include at least one such selection on a boost switch in the treble channel and will also reserve provision for, perhaps, a three-position selector switch on the rear panel.... An interesting wah-wah effect is obtained by operating the boost switch between its two positions.

The first sentence is certainly a statement of Thomas's feeling. The extent to which it reflected, or was derived from, Denney's views and suggestions not clear.

10: - little is said of the power sections of the 30W and 100W prototypes. Both were designed for a 2 ohm speaker load. Dick recommended four Celestion T1088s for the 100W amplifier. He did not like the JBLs that were demonstrated, a point to be taken up in a coming post.

Development and design clearly had a good way to go. The new range was first demonstrated to the trade (and publc) at the Hilton Hotel in New York, late June / early July 1966, an event arranged by Marv Kaiser, head of sales for the Thomas Vox Division.

As for "resonant" or Mid Range Boost, Dick of course had already exploited the effect, demonstrating it on his protoype Guitar Organ in late 1964 / early 1965. Dick never let an opportunity to show the Guitar Organ off slip by.

The novelty expressed by Thomas? Largely as was stated. The incorporation of the effect in guitar amplifiers.

30th June

Continuing the series of notes (begun on 25th June) on the Thomas Organ and JMI solid state amps, an overview of the character of the circuit boards (and potentiometers) in a pre-production Defiant (later 1966).

Pre-production Defiant. From left to right: mixer board (standing transversely); reverb; treble channel; tremolo (to the right, above); normal channel. JMI and its contractor (Burndept) experimented with different positions and formats for these boards during the second half of 1966.

NORMAL CHANNEL BOARD: as Thomas (June 1966 circuit diagrams), not as standard JMI production amplifiers (1967).

BRILLIANT CHANNEL BOARD: not as Thomas. Aligns with JMI production amps (though not identical). All known JMI pre-production amps have variable distortion though - including the Conqueror displayed in London in August 1966. When Thomas did come to work it in later (see yesterday's entry), it was invariable, either on or off.

TREMOLO BOARD: still to be examined, but likely to be much as Thomas. Allowing for a few differences here and there the Thomas circuit aligns with the one found in JMI production amps.

MIXER BOARD: entirely different from Thomas. The circuit is much the same as the one in JMI production amps.

REVERB BOARD: not as Thomas. Aligns with JMI production amps (though not identical).

These for the time being are the bare facts.

29th June

The famous fancy Conqueror footswitch with indicator lights, photographed at the Trade Fair in London, late August 1966. In later '66 the familiar ovoid three-button switch appears. Ultimately this alone was produced. So far as one can tell, nothing further came of the fancy switch (in the 1960s at least).

The earliest production Thomas solid state amps - the V14 and V114 (where the Super Beatle is concerned) - had a plain three-button unit to start with however, much as the simpler Jennings footswitch in terms of function, but switching MRB (with a momentary switch) rather than distortion.

With the introduction of distortion in later '66, Thomas produced a four-button version, this time with a lamp.

Safe to say, JMI was prime mover in both respects. Distortion, recommended by Denney in late 1965 / early 1966, evidently did not find favour with the Thomas engineers, presumably Jacobsen included, early on.

London, late August 1966.

Detail from the JMI solid state catalogue drawn up for the Australian market, late 1966.

Note the "knock-outs" for further switches. The smaller roundels were for letters to designate the effect in view however, not lamps, as only the larger blanks go all the way through the case.

Detail of another early three-button unit, the MRB switch removed.

Detail of a Super Beatle V114 and its switch above.

Thomas Organ service addendum dated October 1966.

28th June

OK - in order to separate out the various strands in the development of the JMI and Thomas Organ solid state lines, an annotated chronology is required. There are for instance a number of difficulties in Sava Jacobsen's letter published on the , some outlined on various forums a few years ago.

Questions naturally arise also - sometimes related - from the report made by Warwick Electronics (effective owners of Thomas Organ) of Dick Denney's visit to Sepulveda in October 1965 published in "The Vox Story", ed. Denney and Petersen (1993), pp. 141-146, Denney ever the diplomat (well, for the most part - we'll come back to that).

The new Thomas Organ range was displayed and demonstrated for the first time in public at the Hilton Hotel in New York, late June / early July 1966, i.e. 10 or so days before the NAMM Show in Chicago. The NAMM Show was the more important of the two events though. The earliest advert for the new amps in the American music trade press is from June, nothing prior to that so far.

The new Fender solid state range was shown for the first time to general public and trade at the 1966 NAMM Show too (10th-14th July '66).

JMI's Conqueror and Supreme were displayed and demonstrated at the Russell Hotel Trade Show (in London) in late August '66. Whether bass models were exhibited is not known at present. One person who may know, and who was at the show, is still around (the question asked).

As the chronology may take a little time to set out properly, certain ancillary things will be illustrated in the meantime.

27th June

Some notes on JMI's work on transistorisation in the late 1950s and early 1960s - simply an overview of the main items. Safe to say there was naturally a good deal more than is mentioned below. The Tonebender is too much of a hot potato still.

1959: - a transistorised add-in effects module for Jennings organs. The effects offered were: percussion, echo, vibraphone, harpsichord, chimes, bells, celeste, marimba, glockenspiel, harp and piano. Some of these are likely to have been re-purposed later for the Guitar Organ.

1962: - a large number of accessories and instruments, principal among which: the Vox T60 amplifier (with transistorised tremolo); the Continental organ; and the Radio Microphone. It is likely that Denney began work on the Guitar Organ at around this time.

later 1964: - Dick's prototype Guitar Organs, with a Mid Range Boost (MRB) circuit. The circuit was termed "contrast" at this point. Mid Range Boost was invented by Dick, and can be heard in a film clip (early 1965) of one of his demonstrations of a prototype Guitar Organ.

1965: - the Guitar Organ in marketable form; a transistorised front end developed for the new MC50/6 and MC100/6 Public Address amplifiers. Work on the two-manual Super Continental organ. A transistor amplifier developed for the Line Source 40 speaker columns. A set of such columns, the amplifier housed in the top of one of the cabinets, was shown at the Russell Hotel Trade Fair in August 1965.

1965/1966:- the 4- and 7-series amps. Rodney Angell, who worked at JMI from the early 1960s to 1968, was clear that the electronic design of the amplifiers (as we have them) was farmed out to an independent contractor (not Triumph, name to be given in due course). The power sections were based on circuits drawn up by Jennings in 1964. Contemporary newspaper reports record that work on the new models had been a matter of great secrecy; and this seems to have been so even within JMI. Rodney indicated that only the R&D Department (of which he was a member from 1965) knew the detail.

Late 1965: - Dick Denney assists Thomas Organ, his activities (at that point) recorded in "The Vox Story", ed. Denney and Petersen (1993), pp. 141-146 (well worth looking out).

1965/1966: - work begins on the new fully solid state range. The line generally used to be that the project would have been realised sooner were it not for the unreliability (read "unknown track record") of silicon NPN power transistors. Early versions of the Conqueror and Supreme were at any rate shown in all their glory at the Russell Hotel Trade Fair in August 1966.

To come: the Thomas preamp boards, and the boards of two of the pre-production JMI solid state amps.

26th June

A note on "modularity" - standardised interchangeable chassis or assemblies, as in the case of JMI's solid state preamps, a Treble version common to the Virtuoso, Conqueror, Defiant, and Supreme; and a Bass version common to the Dynamic, Foundation and Super Foundation Bass. Power sections were common in pairs according to output: 30W for the Conqueror and Dynamic Bass; 50W for the Defiant and Foundation Bass, and so on.

The first company to embrace modularity in any serious way in the United Kingdom seems to have been Audix, which brought a range of Public Address amplifiers to market in 1961/1962. Different types of front end (suitable for required purpose) could be swapped in and out. Power sections were available in 15W, 30W, and 60W versions - which turned out to be three of the increments adopted by JMI for its 4- and 7-series amplifers in 1966. Audix advertised its designs mainly to (and through) the "Association of Public Address Engineers". Jennings joined the Association in 1963.

And it is probably no accident that Jennings's first range of modular amplifiers was not the 4- and 7-series, but the "Metal Clad" Public Address amps, introduced in 1964. The 30W, 50W, and 100W Metal Clads had a common preamp (same size, same circuit), only the power sections differed. The preamp of the 15W version followed the designated circuit but was built on a smaller assembly.

Thomas Organ took its cue from JMI. As has been mentioned, the company's engineers had no experience whatsoever of guitar amplifier design and manufacture before Jennings came along.

A short history of the company written in the 1980s records the sad spectacle of Thomas salesmen in Beatles wigs trying to sell equipment they simply didn't understand. This was not, however, universally the case. Good numbers of dealers knew exactly what was what. Marv Kaiser, the head of Thomas's Vox sales division, was a key driving force.

That Thomas Organ solid state amps should have been modular is no real surprise though. Some notes on their mind-boggling wiring to come. A multitude of sins buried deep in the case of a console organ is one thing, a guitar amplifier preamp ...

Below, a quick shot of one of the adverts placed by Audix in the trade press in 1962:

Audix advert, 1962.

25th June

Posted yesterday on the : - One thing that has been lost sight of in commentary on the Vox T60 amplifier is that the topology of its power section (as it stood in 1963) was used some years later by JMI for the range of state amplifiers introduced in 1966-1967: the Traveller, Virtuoso, Conqueror and Dynamic Bass, and the Defiant and Foundation Bass. The Supreme and Super Foundation Bass differ in certain respects, but their lineage is clear.

The claim, sometimes made without qualification, that this range was somehow simply a poor cousin of the solid state range marketed by the Thomas Organ Company (Sepulveda, California) - the Vox Buckingham, Vox Super Beatle, and so on - unfortunately does not wash. One has to remember that Thomas did not enter the business of designing and manufacturing guitar amplifiers until JMI came along. In the autumn of 1964, Jennings appointed Thomas the sole distributor of JMI equipment in the USA. Up to that point Thomas had only made and sold organs and accessories.

As for those organs, there is nothing remotely similar to the T60's power section (scores of Thomas circuit diagrams survive). Transistor circuitry was confined to voicings and effects. And just to note, JMI had its own transistorised organ effects unit too - in 1959.

As the "Vox Story", ed. Dick Denney and David Petersen, revealed long ago, one of Dick's tasks in late 1965 was to advise Thomas on the development and fitting out of its new range of amps. One of the items presented for comment was an engineering prototype of the solid state Super Beatle, which evidently took some months to bring to saleable form (first advertised publicly in June/July 1966).

In early 1966, David B., an occasional contractor for JMI, happened to be present when a Thomas-made amp sent from the States - presumably solid state - was put through its paces at the Vox Works in Erith. Unfortunately it turned out that the engineers at Sepulveda had either misunderstood or deliberately altered the circuit that JMI had supplied. The result was a source of some concern and amusement (Dick and Derek Underdown are said to have almost fallen over laughing). Nothing is known at present of the tenor of the response made to Thomas.

More to follow in due course.

Detail of JMI circuit diagram OS/062 for the T60, germanium PNP transistors. JMI unforttunately failed to include the variable bias resistors recommended by Mullard for such circuits, something that simply added to inherent difficulties. The circuit would only work properly if everything - transformer windings, currents, voltages, resistances, etc - was perfectly balanced.

Detail of JMI circuit diagram OS/133 for the power section of the Vox Conqueror and Dynamic Bass, silicon NPN transistors thoughout.

Below, a list of Thomas Organ Company transistor part numbers and types from its pocket manual (for dealers) of later 1966. The "Original Equipment Number" is the number given for the transistor or transistors in the parts lists for the various models in the Thomas "Amplifiers Service Manual".

Thomas rarely disclosed the conventional (commercial) name of transistors - i.e. the 2N3055 and so on - in its service manuals. Even the pocket manual only discloses the "Emergency Commercial Substitution Number" occasionally.

- Seven amps had germanium output transistors: the Pathfinder (V1011); the Pacemaker (1021); the Essex Bass (V4 and V104); the Buckingham (V12, V112, and V1012); the Viscount (V15, V115 and V1015); the Cambridge Reverb II (V1031); and the Berkeley Reverb (V1081).

- Two had 2N3055s: the Royal Guardsman (V13, V113, and V1013); and the Super Beatle (V4 and V114). It may be that the very earliest amps had something different. There are unverified reports of germanium.

Late 1966, Thomas dealer manual.

24th June

The page on Supreme serial number 2268's speaker cabinet , linked to the other pages on the amp.

23rd June

Shots of the preamp of Supreme number 2268 . Details of the speaker cabinet still to come (on a page of their own).

22nd June

For VSEL Supreme number 2268, there is and a , details of the preamp and speaker cabinet to come.

21st June

Some pages coming shortly on VSEL Supreme serial number 2268 from later 1969, still in superb condition: complete with its tilt-back stand, footswitch, and covers. Thanks to Mark for the pictures.

20th June (2)

Burndept divided the power section of the Supreme into various numbered sub-assemblies, not only for procurement purposes, but for the assembling and wiring up on the work benches:

67645: components on the main chassis, top and underside, and back panel.

67649: heatsink assemblies.

67650: a mains lead and plug (NOT the socket on the back panel, which was encompassed in 67645).

67661: the wiring looms.

67663: the small 4-way diode board.

67664: the driver / output board underchassis.

67665: the bias boards.

There is nothing to indicate at present whether the gaps in the numerical sequences have any significance. The assembly as a whole was 67571.

The parts roster for the Treble preamp - common to the Virtuoso, Conqueror, Defiant, and Supreme - must have run to a couple of dozen sheets at the very least.

20th June

Details of a couple of information panels on the Burndept parts sheets for the Supreme/SFB. The process evidently began in November 1966, though at this stage the amplifiers were still in pre-production form, as they were also in December and January 1967 - see the surviving examples .

The entries for March, April, and August (issue numbers 4, 5, and 6) will be for runs of standard production amps, probably batches of 100 chassis in each case.

A further sheet contains the remnants of a date under issue number 7, apparently November 1967, so the lists as we have them are from that time rather than August.

Detail of the sheet with the remains of a date under "Issue 7" - November 1967.

19th June

August 1967, a Burndept parts roster for the power section of JMI's Supreme and Super Foundation Bass amplifiers. 100 assemblies were envisaged and provisioned for in this batch. Reference is made periodically to JMI's mechanical drawings - for the control panel, the drilling of the heatsinks, and so on.

The notes on the final sheet indicate that such rosters were drawn up for previous batches too. AC30s, AC50s, AC100s, organs, and accessories, were presumably documented in much the same way. Burndept must at one time have had cabinets bursting with paperwork relating to JMI contracts.

That the procedure of making such rosters went back at least to 1966 is clear enough, having perhaps begun in mid 1964, when JMI moved into Burndept's West Street Works. Whether it went back further - to 1962, say - is unknown.

A class of documentation currently lacking is the Burndept build sheets, i.e. the sheets created for the assemblers on the work benches. Stories used to pop up occasionally along the lines of: "I know a man who knows who has them" sometimes followed by mention of Eric Snowball. But alas, no. Fun all the same.

At any rate, if anything is certain it is that the circuit diagrams sent out by JMI to repairmen and hobbyists - the OS and other series - have (and had) precious little relevance to the actual assembly of chassis.

Further notes on the Supreme/SFB components lists to come.

One of the sheets for the "J.M.I 100W Amp. (P.A. Chassis)", "P.A." being power amplifier.

25th May

Thanks to Josh, some pictures coming of JMI wah pedal - "grey wah" - serial number 5487, circuit still glooped with black resin.

16th May

There is now a . A page on the power section to follow shortly.

10th May

Some pages coming soon on the preamp and power section of Vox Supreme serial number 1133. Shots of the cabinet . Thanks to Mark for the pictures.

7th May

Two picture pages have been added on Vox Defiant serial number 1451, still in fabulous condition - , and . Thanks for Mark for the pictures and info.

Vox Defiant serial number 1451.

3rd May

An entry for Vox Traveller serial number 1126, a really fine example, . Thanks to Mark for the pictures and info.

Vox Traveller serial number 1126.

19th April

Some updates on their way, including shots of Foundation Bass serial number 1548, the latest FB made ready for sale by JMI, "AMPLIFIER" alone at the head of its serial number plate.

24th February

April 1971, the new V100 on the front page of "Music Industry" magazine, introduced as one of the blurbs said "in response to demand following the success of the Vox AC100". The main page on the V100 .

23rd February

Thanks to Ian, shots of Vox V100 serial number 1048 (paired with a VSL Foundation Bass speaker cabinet) .

16th February

"Exchange and Mart" magazine, January 1968, a second-hand Vox Wah-Wah pedal for £9, either grey or Queen's Award, no more than 9 months old.

14th February

Below, a detail of an early PA50SS, its logo visibly different from those of later units. In company with early PA100SS, early PA50s had metal grilles rather than plastic vents; and 7-series knobs.

PA50SS serial number 1289.

12th February

Some shots coming of "Vox Sound Equipment Limited" PA100 serial number 1126, autumn 1969, still the first main version of the model with metal vents and 7-series control knobs,

4th February

Thanks to Gerard, some pictures coming shortly of a superb Supreme, very little changed, serial number probably originally in the lower 1100s.

  • Vox Supreme amplifier section, later 1967
  • Vox Supreme amplifier section, later 1967

30th January

Entries for two Vox Virtuosos without reverb have now been : serial number 1124, sold in Germany; the serial number of the other, sold in the UK, unknown. The former still bears its original shop plaque: Roman Mollenhauer Musikhaus, Fulda.

27th January

Entries for three more Supremes have been : serial numbers 2216, 2263, and 2478.

26th January (2)

Thanks to Christian, pictures of "Vox Sound Limited" Supreme serial number 2325 .

Supreme serial number 2325.

26th January

Pictures have now been added to the entries for three early : serial numbers 5074, 5222, and 5324.

23rd January

Vox Travellers first: , serial numbers 1040, 1098, 1132, and a further example (serial number unknown) sold by "Vox Sound Equipment Limited". Thanks to Richard for pictures of 1132.

22nd January

Some updates coming soon across the range: amplifiers, speakers, pedals, etc.

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