List of updates / new info. on Vox solid state amps (1967-1972)
31st August (2)
Some initial notes and pictures on the preamp circuit boards in the JMI solid state amps. For the treble amplifiers there are five in total: Mixer, Brilliant channel (and distortion), Normal channel, Reverb, and Tremolo. Those in the pre-production amps had both part numbers and descriptive legends:
The "TREMOLO" board in a pre-production Defiant. The part number unfortunately is partly obscured by the solder joints for the connecting posts.
Standard production boards had only part numbers:
Mixer: = Part no. 86021
Normal channel: = Part no. 86022
Reverb: = Part no. 86023
Tremolo: = Part no. 86024
The Brilliant channel (and distortion) board is either Part no. 86020 or 86025. Confirmation will be added in a future post.
Below, some pictures of the undersides of three boards from the wreck of a JMI Defiant. "B", "C" and "E" stand for the legs of the transistor - base, collector, and emitter. The copper traces on these boards are extremely well bonded to the paxolin support. When the components had been soldered on (and presumably testing had been successful), the undersides were varnished.
Normal channel board.
Tremolo board viewed side-on to show the brackets and the gold-coloured plastic stand-offs.
At present it is not known who made these boards - possibly Burndept, or a contractor habitually used by Burndept.
Having said yesterday that no JMI wiring diagrams were currently known to survive in Supreme speaker cabinets, one has of course just turned up. A better picture may be forthcoming.
Speaker wiring labels in Conqueror and Defiant cabinets have survived reasonably well - they were normally pasted to left-hand side inside the cabs.
Above, the paper schema glued inside JMI Vox Conqueror speaker cabinets, its main legend reading: "CONQUEROR 30W TREBLE WIRING". Note that the drivers, in this case Celestion alnicos T1088s, are rated at 17W each - "12" - 8ohm - 17W".
Above, the paper schema glued inside JMI Vox Defiant speaker cabinets, its main legend reading: "DEFIANT 50W TREBLE WIRING". The Midax horn is protected from bass frequencies by a 2 micro farad capacitor (2uf), marked "2 MFD" in the schema.
So far no such diagram has come to light in a Supreme speaker cabinet - a surviving one at any rate. But it is clear from a photo taken in Warsaw on 13th April, 1967, that Supremes did indeed have them - early ones at least.
Detail from a picture of Mick Jagger standing in front of one the Supremes issued to the Stones in mid March 1967 prior to the European tour of 25th March to 17th April - see this page.
The picture comes from this fabulous book published in 2012 - tons of pics of the Stones on stage with their new solid state gear:
The page on Supreme speaker cabinets has now been updated and rearranged along the lines of the other treble amplifier speaker cab pages.
A Supreme speaker cabinet and trolley from mid 1967. Details can be seen on the page linked above. The trolley still has its "T nuts" for fixing the amplifier section to the frame.
The page on Defiant speaker cabinets has now been started.
Thanks to Martin Kelly, whose collection of all things Vox is beyond compare, a picture of a Vox Checkmate guitar tuner. The page on the Checkmate has been updated correspondingly.
The unit above is a six note tuner - "Unit One" as described and pictured in April 1972.
25th August (2)
The page on Conqueror speaker cabinets has now been updated. A companion page on Defiant cabs will be posted soon.
A note on Defiant speaker cabinets to complete the series of notes on Conquerors and Supremes in the previous few entries.
1967 to spring 1968 (JMI): 300 Defiants sold. Speaker cabinets were not available separately.
late 1968 to late 1969 (VSEL): in total around 360. From number 001 to between 318 (highest known VSEL) and 375 (lowest known VSL).
early 1970 to late 1970 (VSL): around 400. From number 375 (or before) through to 785. VSL sold a number of Defiants and speaker cabinets made by VSEL.
24th August (3)
Some details from the pictures in the previous entry showing amplifier boxes waiting to be covered, and a stack of Conqueror baffles ready to be fitted to cabinets.
Wooden cabinets for amplifiers (as received from Gla-Rev) waiting to be covered and made ready for use. A finished one sits on top of the smaller pile.
Stacks of finished baffles with grille cloth and white piping.
24th August (2)
Pictures of cabinet finishing in the Vox Works, Erith, taken by Denis Molyneux. These pictures were published with various dates and locations ascribed in their captions. All are from June 1969, however. Note the form of mounting for the side stands on the side of the Conqueror cabinet. This is not 1967.
In 1969, cabinets were generally made by Gla-Rev (Hainault, Essex), perhaps a few when needed by Heslop & Co. (Rayleigh, Essex), and P.A.Glock (Crayford). The units were then sent to Erith for finishing - vinyl covering, cloth for the baffle, and necessary fixtures and fittings.
June 1969. Adding the vinyl covering. In the foreground a Supreme cab - NO - it is a Super Foundation Bass. The glue is common or garden PVA.
June 1969. Conqueror speaker cabinets. Adding the fittings. Note the jig for the drilling of holes for the handle fixings.
Said to have been taken at the P.A.Glock premises in Crayford, but this is actually the Vox Works, June 1969, as above. Note the "V" of the "VOX" logo on the work-coat. Ironing the cloth of a Super Foundation Bass baffle - around 17 diamonds wide.
Just to add that Glock worked more for JMI in the early 1960s - Crayford was little more than a mile up the road from 115 Dartford Road ("Unity House"). Heslop & Co. worked more in the mid sixties - see this page for cabinets in the solid state range. From the mid sixties, Gla-Rev generally produced cabinets for the larger amps.
Picking up from yesterday's entry, a note on Conqueror speaker cabinets. In the JMI period, no serial number was stamped on the cab's plates even though there was space for one. As with the other models in the solid state range, speaker cabinets were only sold with amplifier sections as a set, so the amplifier's number was notionally the speaker cabinet's too.
1967 to spring 1968 (JMI): 580-600 Conquerors sold. Speaker cabinets not available separately.
Under "Vox Sound Equipment Limited", Conqueror cabs could be bought without the amplifier section. Under "Vox Sound Limited" only a small number of Conquerors (and Dynamic Basses) were sold, the model being from the catalogue once existing stocks had been sold.
late 1968 to late 1969 (VSEL): in total around 320-350. From number 001 to between 312 (highest known VSEL) and 366 (lowest known VSL).
early 1970 to late 1970 (VSL): probably around 100. Only two numbers are known definitively at present: 366 and 374. Around 100 VSL Conqueror amplifier sections were sold - see this page.
The very last speaker cabinets to be sent out with Conqueror amplifier sections may actually have been Defiant cabs, "Defiant" dymo-taped over with "CONQ". Presumably it was not worth having a small number of new Conqueror cabs made up.
A Defiant speaker cabinet with "CONQ" dymo-taped across "Defiant" in the panel reserved for the model ("TYPE").
23rd August (2)
A note on Vox Supremes. In the JMI period, speaker cabinets could not be purchased alone. Amp and cab came together as a set. Speaker cabinets were therefore not numbered as they notionally took the number of the amplifier with which they were sold.
1967 to spring 1968 (JMI): approximately 300 Supremes sold.
From the beginning of the "Vox Sound Equipment Limited" period on, that is to say from late 1968, amps and cabs could be purchased separately, so speaker cabinets were numbered.
late 1968 to late 1969 (VSEL): in total around 250. From number 001 to between 236 (highest known VSEL) and 289 (lowest known VSL)
early 1970 to late 1972 (VSL): in total around 300. From between number 236 and 288 through to 543.
Towards the end of the VSL period Supreme speaker cabinets were phased out, and Supreme amplifier sections were issued with Companion cabs instead.
Inspection tags of the three companies that produced and sold the solid state amps: JMI (1967 to Spring 1968); "Vox Sound Equipment Limited" (summer 1968 to late 1969); and "Vox Sound Limited" (early 1970 to late 1972).
JMI Defiant serial number 1102. Final inspection on 24th April 1967. The amplifier is registered here.
VSEL Supreme serial number 2231. Final inspection on 26th November 1969. The amplifier is registered here.
Supreme speaker cabinet number 506. Final inspection on 11th July 1972. Supreme cabs 525 and 528, which also have their tags, were inspected on this day too. Further pictures on this page.
22nd August (2)
"Practical Electronics" magazine, February 1967. The retail price of 2N3055 transistor was 22 shillings and sixpence (22s/6d). The retail price of an EL34 valve at the same date: 9 shillings and sixpence (9/6).
The ratio - the 2N3055 over twice the price of the EL34 - presumably held for wholesale (bulk) orders placed by JMI.
"Practical Electronics" magazine, February 1967.
A note on the slider resistors and potentiometers used by JMI in 1967 in its solid state amplifiers. The slider resistors, which were used to set the bias of the output transistors, were made by the Egen Electric Company of Canvey Island. JMI had used Egen from the early 1960s. For the pots in AC100s, see this page.
Above a defunct bias board from a late JMI Defiant.
The underside of a broken slider showing the wire winding. Resistance was adjusted by sliding the brass sleeve to the desired point.
The Virtuoso, Conqueror, Dynamic Bass, Defiant, and Foundation Bass all had three sliders: 2 x 25R, and 1 x 250R. The Supreme and Super Foundation used five: 4 x 10R, and 1 x 250R. Travellers had Egen trimpots.
Once the ideal resistance had been found, the slider sleeve was fixed in place with varnish or a dab of red paint.
Although the potentiometers used by JMI for the solid state amps have no markings, it is likely that they were made by Egen too - specially for JMI. They are certainly not off-the-peg items. Sometimes one finds it said that they were made by Morganite or Colvern, but neither company made anything matching these.
25K pot from the defunct JMI Defiant.
The same pots are also found, along with other components used in the solid state range, in Vox AC50s from 1967 and early 1968 - see this page.
A new page on the assembly of preamp chassis is coming soon. The general outline in yesterday's entry needs expanding in several respects:
1) Very early Conqueror and Dynamic Bass preamp chassis designate the model of amplifier for which they were destined. "30W T. PRE/AMP SER. No." for the 30 watt Conqueror. "30W B. PRE/AMP SER. No." for the 30 watt Dynamic Bass.
This seems to have been dropped fairly quickly. Preamps were subsequently designated "PRE/AMP T. SER. No." The need to store sets for the different models separately was therefore removed - the units used for the Virtuoso, Conqueror, Defiant and Supreme were all identical cosmetically and electronically in any case.
No examples have yet emerged, however, of chassis stamped "50W T. PRE/AMP SER. No." (for the Defiant) and "100W T. PRE/AMP SER. No." (for the Supreme).
Conqueror serial number 1046. Treble preamp chassis no. 1045.
Dynamic Bass serial number 1135. Bass preamp chassis no. 1001 - either the first or second casing made.
2. When chassis had been assembled, they were tested and inspected. Now and again one finds the remains of stamps.
Foundation Bass preamp chassis. "VIB." is also found on power sections. Later on one finds large numbers stamped.
3. At point of final assembly, numbered stickers were added to the box and its back-board, and to the preamp and power amp.
The various elements could then be reunited if something went astray in the final assembly process, or indeed later on. As the numbers on these stickers do not go very high, batches of no more than a dozen or so were done at a time, and the sequence restarted at "1" for the next.
Some notes on treble preamps - in other words the common unit that went into Virtuosos, Conquerors, Defiants and Supremes.
Preamp chassis casings were stamped out, numbered, and passivated (chemically treated to prevent rust). Certainly in late 1967, Burndept and Vox used the company "Holmes Plating" in Blackheath to do the passivating.
When the chassis were ready, they were populated with components in batches on the workbenches in the Vox Works at Erith, then put to one side in no particular order. It seems that finished preamp chassis could sit for some time.
When the time came for a treble amplifier to be made up, a preamp chassis was selected from the store, along with a suitable power amp section (30W for a Conqueror, 50W for a Defiant, and so on). The two were then fitted into the wooden box.
A serial number plate was added to the backboard, and the number noted in Jack Jennings's register. The serial numbers of the various models were recorded in order.
The amp was then boxed, its model name and serial number written on the outside, and the box stacked in the store ready for despatch. When known, the destination might be written on the box too.
Before the amps were sent out, destination and purchaser were noted against the serial number in the registers.
Below, a digest of known component date codes noted against treble preamp chassis numbers. As one might expect, the higher the chassis number, the later the component date codes, generally speaking. But there is nothing at present to indicate that chassis were populated strictly in numerical order.
A couple of chassis with component dates unknown are included simply to give an indication of final use - in other words the resulting amplifier.
One of the interesting things to emerge from the table is that production of Supremes seems to have lagged slightly behind the Conqueror and Defiant. Serial number 1030 for instance has component date codes of March 1967.
Whether troubles encountered by The Stones - who had standard production units as early as mid March '67 - set the sale of other early Supremes back is hard to say, though it could easily be that JMI was waiting to see. Early Supreme power sections were biased very hot (as numerous incinerated tagboards attest). Transistor / bias failure may have been a real concern in March '67.
By late April 1967, around 100 Defiants had been produced - see serial number 1102 on this page. Presumably around the same number of Conquerors (or perhaps more) had also been made by that point.
A table for bass preamp units will be posted shortly.
19th August (2)
Below, a detail from the full page pre-production advert in "Beat Instrumental" magazine, November 1966 - two guitar tuners. One a simple "E" tuner (possibly bearing some relation to the American unit), the other a six-frequency device.
Only the "E" tuner made it through to production. But it may be that the design of the six-note tuner was taken up "Vox Sound Limited" in the process that led up to the creation of the Vox Checkmate tuner in late 1971 / early 1972.
"Beat Instrumental" magazine, November 1966.
JMI retail pricelist, April 1967.
Along with further tidying up, there is a new page now (gathering together some of the disparate notes) on Twickenham and Lemark transformers, used by "Vox Sound Equipment Limited" from 1969 to 1972. The units are instantly recognisable by their unpainted shrouds. Those of the transformers used up to early 1969 were invariably black.
Below, a detail from a great shot of The Animals at the "International Love-In", Alexandra Palace, London, 29th July, 1967. The Supreme amplifier sections have white markers(?) on their grille cloth. At 1.13", one gets a glimpse of the markers in the film clip too, shot in Berlin on 12th January, 1968.
Alexandra Palace, 29th July, 1967.
Live TV Show: "Berlin bietet Beat" - 12th January, 1968.
Various elements on the site are in the process of being updated. If anyone comes across broken links, items that won't resolve and so on, do let me know.
The page on four "rejected" units exhibited at the BMII Fair in late August 1967 has been expanded.
The JMI German catalogue of March 1967 is now available in its entirety here. Move back and forth via the links at the foot of the pages.
The page on pre-production Vox solid state amplifiers has now been tidied up. As one might expect, there's more to the story of the English and American Vox solid state amps than has hitherto come out - but that's for another day.
Also to note that the page on one of the pre-production Defiants now has its thumbnails back.
15th August (2)
A small diversion: the Vox Checkmate guitar tuner, designed in late 1971 and signalled in "Beat Instrumental", the "Vox Sound Limited" catalogue of 1972, and "Music Business Weekly" magazine. A grand total of none surviving? Perhaps there are some somewhere.
The device was one of the first non-strobe electronic guitar tuners on the market.
"Beat Instrumental" magazine, January 1972.
"Beat Instrumental" magazine, April 1972.
Vox general (selective) catalogue of 1972.
"Music Business Weekly" magazine, 4th March, 1972 - pieces on the Frankfurt Music Fair of that year.
The chronology outlined below has now been set up on a page of its own - available here - with images interspersed and further links. The page on production has been updated correspondingly, middle and end in particular.
The page on pre-production amplifiers will be given a shake up shortly.
14th August (2)
A slight adjustment below (a correction). The Frankfurt Music Fair (Musikmesse) of 1967 took place from 26th February to 2nd March, not mid March as initially stated.
Below, a detail from the JMI promotional page for the new solid state amps published in "Midland Beat" magazine, March 1967. The full page along with a related page in the issue for April '67 is here.
Among the things of interest is the remark that the solid state amps - to be shown at the Frankfurt Musikmesse (26th February to 2nd March, 1967) - "will remain on the secret list until the opening day of the Fair" - secret at any rate to the continental market.
The German catalogue - entry for 7th August below - was clearly drawn up with the Fair in mind, the new solid state amps outlined on the final two pages.
The lead-up to the arrival of the solid state range was bumpy though, and has led various commentators astray. Some of the documentation can be found on this page, but it is probably worth restating the chronology here.
Mid 1966: Design and prototyping.
Late August '66: a promotional Vox Conqueror exhibited at the BMII Trade Fair at the Russell Hotel, London. The JMI brochure for the Australian market reproduces the first attempt at a footswitch.
Late 1966: a small number of pre-production amplifiers are made in the Vox Works at Erith. A surviving pre-production Dynamic Bass has its original inspection tag dated 12th January 1967.
Late 1966 / early 1967: the pre-production amps were given to bands to try. Manfred Mann and Blossom Toes were issued with Supremes. Manfred used his until c. 1970 with a Vox 4120 speaker cabinet.
Early January 1967: the announcement is made in "Beat Instrumental" magazine that the new range would be available at the end of the month. But this did not happen.
Probably late January / early February 1967: the range is redesigned, cosmetically and electronically. Feedback from the bands on the pre-production models had doubtless raised some difficulties.
February and March 1967: advance production of the new designs begins.
Late Feb. / early March 1967: the new solid state amps are "a secret", for the continental market at least, until the Frankfurt Musikmesse. The German catalogue is printed to coincide with the Fair.
Mid March 1967: The Stones are issued with two standard production Supremes and a Super Foundation Bass amplifier.
April 1967: the new JMI pricelist for the UK is issued. "Beat Instrumental" magazine relates elliptically that the range is now available.
13th August (2)
The page on Super Foundation Bass speaker cabinets has now been updated.
Pictures of a Vox Super Foundation Bass cab from c. 1970-1971 - produced by "Vox Sound Limited". Note that on the serial number plate the unit is termed a "Super Twin Bass". Thanks to Rey for the pics.
By mid 1972, that is to say close to the point at which VSL folded, such cabs were termed "Super Twin Foundation Bass", the highest serial number so far encountered being 294.
For Super Foundation amplifier sections and speaker cabinets made during the VSL period, see this page. Approximately 300 were produced and sold, early 1970 to late 1972.
Cab serial number 092.
Below, pictures of the Vox catalogue issued for the German market in March 1967 - "III/67". The amplifiers of the solid state range appear at its end - they were not quite ready for release at the time though. Note that the bulldog emblem, which was quietly omitted later, also appears in the early catalogue produced for the Australian market, again before the range was ready for sale.
In effect, the catalogues were promotional. The solid state range did not officially come to market in the UK until April 1967 - shipments are unlikely to have reached Europe or Australia much before that, even though orders had been placed by foreign dealers in late 1966 and early 1967 (at the BMII and Frankfurt Trade Fairs).
The copy above was supplied to "Piano-Werner" in Sraubing, Lower Bavaria (Niederbayern).