List of updates / new info. on Vox solid state amps (1967-1972)
January to May 2021
Currently on kleinanzeigen, JMI Dynamic Bass serial number 1164 complete with covers, cables, and the Vox brochure printed for Mufag, one of the three West German distributors and presumably the supplier of the amp.
Thanks to Nikolaj, pictures of Conqueror serial number 1033 - brown control panel, good external order. The legend for the Top Boost switch is the standard one: OFF/ON rather than the variant OFF/MRB.
Pictures of "Vox Sound Equipment Limited" Supreme serial number 2020 now added. Thanks to Derek.
19th May (2)
Below, the PA50 in the JMI catalogue of April 1967. The PA100, depicted on the other side of the brochure's gutter, looks much the same. There are four microphone inputs, one music. The five channels apparently each have volume, treble and bass (volume above the socket); and there is overall volume, treble and bass at right. The amps in a sense bridge the gap between the all-valve MC amps (three mic inputs, one music), and the MC units with transistor preamps (five mics, one music). But the MC PA amps only have treble and bass controls for the master volume.
The knobs on the fascia of the amps pictured in the catalogue have numbered skirts and are probably the same as the ones used for the 7-series. Note that there are no legends for the controls though - only for the inputs and the "Master" at right. Nor has the indicator lamp underneath the master volume control been given any caption. ON/OFF and STANDBY switches will been on the rear panel (as in the solid state guitar and bass amps).
The two units as illustrated were presumably mock-ups for the catalogue. Quite how many were actually produced is hard to gauge - there are certainly entries for both in the pricelist of April 1967 - the PA50 at £105 12s 6d; and the PA100 at £134 - but none has ever been seen (or at least noticed).
Their presence shows though that the move towards fully solid state PA amplifiers had begun at least a year before SSC/004 (see below) had been drawn out.
Thanks to Rodney, a copy of circuit diagram SSC/004 - the Vox solid state PA50SS - coming soon. SSC/004, drawn up in March 1968, still in JMI days, later became "Vox Sound Equipment Limited" sheet OS/177, with three sets of additions, February to October 1969.
Additions aside, SSC/004 differs from OS/177 in four main respects. Certain parts are drawn differently (esp. at the output); signal voltages are not given; three of the printed circuit boards have JMI numbers: J.M.I./93 to J.M.I./95; and the layout sheets referenced are SSL/001 to SSL/003 instead of A222 and A241 in OS/177.
Note the two types "SSG" and "SSP" - "Solid State General Purpose" and "Solid State PA"? But it would make little sense then to say "PA Amplifier". In the circuit diagram an alternative transformer-based impedance-matching microphone input is represented for the "SSP", so perhaps the distinction was rather the type of microphone envisaged.
Two Dynamic Bass sets, probably exported to Germany in early 1968, possibly serial numbers 1181 and 1182, but more likely 1182 and 1183 - the final numbers in both cases are slightly damaged. 26th May - These are actually the same amp - note the mark on the cab's grille cloth. The dents in the serial number plate do not show in the second set of pictures:
Currently on ebay-kleinanzeigen.>
8th May (2)
Three Dynamic Basses to come, two with consecutive serial numbers, both in Germany.
7th May (2)
Currently on Reverb, Supreme serial number 1066. Thanks to Matt for the info. The resistor in the DIN socket is simply there to jumper the distortion on.
21st April (2)
"Melody Maker", 23rd December, 1967 - Vox solid state equipment for sale, probably little more than six months old. It is interesting that the most coveted thing these days among the items listed is the grey Wah pedal, ironically produced in the greatest number.
"Melody Maker" magazine, 7th September, 1968, a rotating speaker unit by Park - principally to give some context to Vox Gyrotones and JEI "Pulsation" cabinets. The Park "Tremulant" unit has a 15" Celestion speaker, and fully variable rotation speed. Vox and JEI simply had slow and fast.
An advert placed by Macari's in "Melody Maker", 19th April, 1969 - Gyrotone ("Gyratone") 1s for 55 guineas (£57 and 15 shillings). Macaris were in the old Jennings shop on Charing Cross Road, expanded to take in number 102.
A new page on Gyrotone III rotating speaker cabinets has now been posted here. To come - the Gyrotone IV and a page on the Gyrotone 50 and 100 (with built-in Midas amplifiers).
Below, "Vox Sound Limited" Supreme cab serial number 272 - an early VSL unit. Note the blue-framed Goodmans speakers (with "Vox Sound Equipment Limited" labels). The page on Supreme speaker cabinets has been updated.
The new page on the Vox Gyrotone II (1967-1973) has now been started. Early cabinets (1967-1969) had a split front, the upper section sloping in a similar fashion to the upper front half of the Gyrotone I. In late 1969, "Vox Sound Equipment Limited" introduced a new-style cabinet, near cube in shape. At much the same time, "Jennings Electronic Industries" (JEI), Tom Jennings's new company, released the "Pulsation PO.1" - effectively a Gyrotone II in an early-style cabinet. It seems likely that JEI took over surplus early cabinets, either from VSEL or the cabinet maker.
The new page on the Vox Gyrotone I (1967-1968) has now been started. The existing rather untidy general page on Gyrotones will be left in place until the new pages on the Gyrotone II, III and IV are ready.
Detail from the JMI catalogue of Spring 1967
A "Vox Sound Limited" Defiant - serial number 2756 - with two of its coloured control knob inserts intact.
Below, a JMI Virtuoso and a VSL PAR100SS with full complements of inserts. It may be that these were supplied in a small packet, to be fitted by the owner if desired.
VSL PAR100 (PA 100 Reverb), serial number 1132.
A recent arrival: a copy of circuit diagram OS/137 for the preamp of the Dynamic, Foundation, and Super Foundation Bass amplifiers. The sheet was added to in 1969, during the "Vox Sound Equipment Limited" period. At some point after 1970, VSEL's name was erased to make way for "Vox Sound Limited" (1970-1973).
The info panel.
Register of changes in the upper left corner; (1) 1-11-66; (2) something ADDED 24-11-66; (3) a component value changed 8-2-67; VOLTAGES ADDED 31-3-67; (5) LAMPS ADDED 22-3-69 (perhaps 22-5-69).
The info panel of the JMI sheet. This version only has changes to April 1967 and lacks the lamp schema in the lower right hand corner.
The sheet as a whole.
A series of updates coming for Vox Gyrotones - prinicpally dedicated pages for the various models, the Gyrotone I, II, and III, and the later Gyrotone 50 and 100.
Conqueror serial number 1440 now added. The amp was brought to Sweden by the importer / distributor Muskantor & Co. in Goteburg. Muskantor also imported equipment made at the E.M.E. factory in Recanati, which had been been set up in 1966 by Jennings, Thomas Organ, and Ekco.
Thanks to Matt, pictures of Conqueror serial number 1153, long in Australia and perhaps originally sold there.
A further note on the solid state circuit diagrams. Those that have survived complete have lower left, after Jennings etc. "The Royston Group of Companies", and at top right, the Royston symbol (as in the image below). Royston was the company that had taken a controlling interest in JMI in late 1962 / early 1963.
A reliable printed source has just come to light - to be published soon - signalling that Royston had set up a new Design Drawing Office in late 1966 off West Street in Erith - presumably in the West Street Works (though that will have to be verified).
At any rate, the diagrams that mention Royston so prominently are likely to have been made in that Office. Known diagrams for the 7-series amps, released in 1966, make no mention of Royston, only Jennings.
A detail of OS/133, the sheet for the power section of the Conqueror and Dynamic Bass.
Rainer Baumann of "Frumpy" with a V100 amplifier on two red vinyl Marshall 4x12s on Beatclub in 1971. The page on the V100 has been updated.
Screen-grab from the YT clip below.
Below, an ad placed by Pepper Music in "International Musician and Recording World", February 1976. On offer, a Vox Multi-Link II speaker cabinet - 2x12" + 2x15" speakers. See this page for some surviving examples.
"International Musician and Recording World", February 1976.
"Music Maker" magazine, Australia, December 1968. The "Rubber Band" with a new Foundation Bass amp.
Just to signal the presence of Traveller serial number 1226 on ebay in the UK - good condition, original Celestion T7442 still in place.
Below, a copy of the JMI circuit diagram for the "grey wah" - OS/158, and the "Preliminary Schematic" issued by Thomas Organ in April 1967 as part of its Accessories Service Manual.
Leaving aside general layout, the chief differences lie in the inductor and the elements around it, and in the provision in the JMI drawing for what would seem to be a battery ON/OFF switch (not implemented). From the look of things, the JMI circuit is earlier.
The BC150 transistors were later changed to 2N3707 as production gathered pace. The circuit boards of the earliest pedals were glooped with a black adhesive cement to prevent copying. See this page.
The story, according to JMI sources, of how the wah came to be invented will be related shortly. See the entry below, 9th February, for a link to the story as remembered in the US.
10th February (2)
Some more pieces relating to the months following the demise of Vox in 1973. Below, a notice in "Beat Instrumental" magazine, September 1973. George Stow, who had been a major force in the creation of "Vox Sound Limited" in January 1970, and who became its managing director in February 1971 - see this page - set up Roxburgh Sound (also know as Roxburgh Electronics) in the summer of 1973. A good deal of surplus Vox stock went with him - there's an advert in "Melody Maker", July 1973, which notes some of the items available. August was evidently the grand opening, the page in "BI" evidently purely promotional. But the company did not last long. By March/April 1975 Stow was working for Reslo, with which he had done business since the late 1960s.
"Beat Instrumental" magazine, September, 1973.
Some of the old stock was finished off in peculiar ways in Winchelsea, Hastings and elsewhere, which has often led to the cry "prototype!" whenever it turns up. Unfortunately not. Just late VSL bits and pieces turned into a saleable form.
10th February (2)
The page on circuit diagrams (schematics) has now been updated with Pete's new drawings of the Vox Midas (OS/208), copies of the JMI sheets for the Virtuoso and Conqueror/Dynamic power sections (respectively OS/132 and OS/133), and a copy of the JMI sheet for the bass amplifier preamp (OS/137). Further updates to the page coming shortly.
9th February (2)
A strange one. The main picture below - testing solid state amplifiers at the Vox Works, Erith - is said to have been taken on 27th April 1967. The calendar on the wall places something of a question mark over this, however. Weeks in calendars normally begin with Sundays, the day number given in red. The Sundays in view are the 1st, 8th, 15th, 22nd and 29th. The only months in 1967 that fit are January and October.
Additionally, one of the amplifiers on the bench is a PA50SS, its circuit diagram drawn up in March 1968. Assuming that the month shown by the calendar is actually the month current at the time the photo was taken (ie. that someone had not flipped the calendar pages forward or back and left it like that), then which month and year is it? October 1967? January is too early. The PA50SS was certainly not in train then. The only other options are October 1968 and June 1969, both of which are perfectly possible. My bet is on June 1969.
Note in the right-hand corner the transformer for the Vox MC100 valve public address amplifier. The writing on the tape reads "MC100/6 or /4 Mains" - i.e. suitable for the 4-input or 6-input version.
Thanks to Pete, coming shortly, some excellent newly-drawn circuit diagrams for the Vox Midas 100 amplifier. The version of the original - OS/208 - available online is extremely poor. A slightly better copy of a copy survives (details below), but that is also fairly gone in places.
The original was created by the Ozalid process - one can just make out the note lower left. See below, entry for 6th February.
The original date of drawing can just be made out - 29/10/1969, so end of days at "Vox Sound Equipment Limited".
Also coming soon, a JMI circuit diagram for the Vox "grey" wah - OS/158. The story of the "invention" of the wah is told from the American side on this page - and told with due reference to JMI: “If you really want to say who was the grandfather of the wah-wah,” Mr. Casher [Del Casher] says, “it was Dick Denney.”
The story on the JMI side, recently related by a former employee, is slightly different though. And the JMI drawing tends to show that the American circuit - the "Preliminary Schematic" of April 1967 - published in the Thomas Organ Accessories Manual is a derivative. More to come.
The two information panels of OS/132, the circuit diagram for the power section of the Vox Virtuoso, which was originally called - throughout pre-production - the Supreme.
6th February (2)
Just arrived, the catalogue printed for Mufag in 1967, mentioned yesterday, along with a pricelist printed for Barth in 1966 (one of the two other main distributors in West Germany), and a further copy of the pricelist from 1968.
The Mufag catalogue is more expensively produced than the version printed for general release - available here.
The Barth pricelist gives prices for the 7-series range in full, along with the AC30, AC50, AC100 and T60, the Vox Metal-Clad (MC) public address amplifiers, and a selection of guitars and accessories.
Some new circuit diagrams and details on the way. For the time being, the information panels of OS/133 for the Conqueror and Dynamic Bass power section.
Note the dates: first drawn out in November 1966; the Standby Circuit rewired in February 1967; Voltages added March 1967 - which is the point at which the solid state range was finally released for sale.
The circuit drawings were made by the "Ozalid" process. A transparency of the drawing would be produced and placed on chemically treated paper. The two would then be exposed to ultra-violet light, and the paper (print) developed with ammonia vapour. The process will either have been undertaken by the Burndept Drawing Department (in one of the buildings near the Works in Erith), or by an external contractor.
5th February (2)
A Jennings Musical Industries wiring diagram for the Vox Supreme, pasted inside a surviving Supreme cab. Most cabs accompanying amplifiers in the solid state range had diagrams of this kind. Thanks to Gwen for the picture.
A Jennings catalogue produced in March 1967 for Mufag, one of the main Vox distributor/agents in West Germany. The cover, as can be seen, differs from the one produced for general release in Germany. Further images to follow.
Detail from an advert placed by Vox in "Beat Instrumental" magazine, February 1969.
Front cover of the catalogue produced for general release.
A video of Vox Discotape serial number 036 in action, thanks again to Malc. If it does not play, click on the link in the video or here:
Thanks to Malc, pictures of Discotape serial number 036. Pics four and five show the power section of the unit during the course of restoration. The 2N5294 transistors have the date code "7106" = 6th week of 1971.
Recently come to light, a wiring schema for the Gyrotone 50 and 100 (formerly the Gyrotone II and III). The drawing is dated 16th July 1970. A full copy will be made available soon.
Note that "Vox Sound Equipment Ltd" has been altered in three places to read "Vox Sound Limited" - twice in the upper panel, and again in the second from bottom. Presumably it took some time for the draughting company - A. & F. Royal Ltd - to update its template. "Vox Sound Equipment Limited" came to an end in December 1969. "Vox Sound Limited" began trading towards the end of January 1970.
A. & F. Royal Ltd was at 22A, The Boulevard, Crawley, Sussex.
The main page on the Vox solid state public address amplifiers is in the process of being tidied up. It will probably be necessary to expand it into three: introduction, PA50SS and PA100S.
In the copy of the Works diagram of the PA50SS - OS/177 (details below, entry for 29th Jan) - the "creation" date of the circuit is given as March 1968 - in other words, it was developed and issued by "Jennings Musical Industries", which remained in business until the late Spring of '68. Changes and additions made during the course of 1968 and 1969 were recorded when VSEL made a new copy of the sheet in late '69.
The sheet for the PA100SS on the other hand only gives February 1969 for first changes, no date of creation. But the circuit is likely to have been designed in conjunction with that of the PA50SS.
Small section of OS/176 for the Vox SS PA100.
Thanks to Jiri, pictures of "Vox Sound Limited" Defiant, serial number 2494, probably produced in mid to late 1971:
A copy of an original "Vox Sound Equipment Limited" Works circuit diagram for the PA50SS, exhibited at the Russell Hotel Trade Fair in August 1968, and perhaps earlier at the Frankfurt Trade Fair in March. The sheet, which measures 35 x 23 inches, belonged at one time to Eric Snowball of E.S.E. Music in Maidstone.
Currently on Reverb, Virtuoso (non-reverb model) serial number 1135, original footswitch and Celestion 7724 speakers (8127 is the part code), excellent condition. Probably produced in the last third of 1967. See this page for info on the model, and details of further Virtuosos.
Virtuoso serial number 1135.
Thanks to Frode, pictures of "Vox Sound Limited" Foundation Bass serial number 2524, in good working order.
Below, an example of the final type of "Vox Sound Limited" inspection tag from an AC30, c. 1972. Note the presence of "Hastings, SX". Earlier tags had the address of the Vox Works at Erith. The move to Hastings took place in stages - assembly and production first (summer 1971), then the offices and showroom (summer 1972). See this page.