Vox AC30 website updates

January 2024

31st January

Below, an example of the two-button footswitch supplied with Italian-made AC30 Top Boost Reverbs, 1971-1972, . The switch on the left is for Reverb, the one on the right for Vibrato.

The pedal supplied with Italian-made AC30 TBR serial number 30202.

The type of casting employed was effectively one that had been designed by JMI in 1966, initially for its range of 7-series "treble" amplifiers (the 715, 730, 760, and 7120), the design taken up a few months later, but with a different wiring scheme, for its fully solid state amps (Virtuoso, Conqueror, Defiant and Supreme). An overview of JMI three-button pedals can be found on .

Pedals issued with the English-made Vox solid state range of amps, 1967-1973, two types of casting, earlier and later.

The Italian casting obviously suppresses the logo and the front-most switch for distortion. The hammerite paint is usually blue/grey rather than the silver/grey adopted by JMI. It is worth noting that "Vox Sound Limited" continued to supply three-button footswitches with the solid state amps it offered through to end of play in early 1973.

29th January

Thanks to Colin, pictures of AC30 serial number 8973, cabinet re-covered and fitted out with Selmer cloth. The Woden transformers have the date codes "HU and "JU" = August and September 1963 for their manufacture. Further pics .

AC30 serial number 8973.

25th January

A new-style Domino Reverb piggy-back amplifier from late 1964 / early 1965 - see the entry below for 16th January and the material . Relatively few were produced (and sold).

Domino Reverb (piggy-back), serial number 3329.

22nd January

Below, a couple of pics of an early Domino Bass - serial number 1280, which suggests that all Dominos from the outset shared a serial number sequence beginning at 1000. That no example of a Domino Super Reverb has come to light so far with a serial number under 2000 may indicate that the model came to production slightly later than the others.

The suggestion that the Domino Bass and Super Reverb shared a sequence beginning at 2000 must be put aside (and has been corrected on the relevant pages - ).

Domino Bass serial number 1280.

21st January

Further to the question of "issues" of circuit diagrams, it is clear that nothing much was done for the AC10 and AC15. The only sheets that have come down to us are OS/008 and OA/031. The former - some copies dated September 1960 - has notes of additions through to March 1963. The latter, first drawn out in April 1960, has one only of February 1961. The values of capacitors were not updated - we find 0.05uf in both rather than 0.047uf. This is likely to have persisted through to late 1964 as Thomas Organ felt obliged to draw up the circuits for these amps anew - and in a broader sense, no wonder. OS/008 and OA/031 were virtually prehistoric. Thomas, accordingly, incorporated the new sheets in its Vox Amplifiers Service Manual, circulated to dealers and service centres from 1966.

Below, a detail from a version of OS/008 issued with no date or list of additions in its information panel. Not all sheets were created equal.

20th January

The section on OS/010 - the Top Boost add-on circuit - has been . It turns out that the diagram was drawn out at least five times (not three):

(1) - as originally drawn by John Bell in December 1961. No copy has come to light so far.

(2) - issue 2, June 1963, but with no changes to the circuit noted. There is no text within the box at top right immediately under the diagram - see (3) below. The only voltage noted is: "HT 230v" at the top of the main diagram. Copies of this sheet were evidently sent out in wallets of circuit diagrams issued by JMI.

(3) - issue 2, June 1963, a version of the above. However, within the box at top right there is a line of text underneath the inset diagram: "MODS TO AMPLIFIER AC30/6. DRAWING NO. A/026. This was the sheet embodied in the Thomas Organ Vox Amplifiers Service Manual.

Detail of the sheet in the Thomas Organ Manual: issue 2, June 1963, but there is no note of what the changes in issue 2 were. The text in purple does not appear in (2) above.

(4) - issue 3, February 1965 (not Jan. as initially stated), the one currently in circulation on the web. Voltages are given throughout - the main HT is now noted as being 320v - and valve pin numbers are provided. Jim Elyea gives a print of an uncirculated copy in his schematics portfolio (sheet number 57). In issue 3, the additions made in issue 2 are listed as being voltages and valve pin numbers.

Presumably there was some version of issue 2 that gave the spread of voltages and the valve pin numbers as encompassed in issue 3.

A detail from the information panel of issue 3 listing what the changes in issue 2 were (or should have been).

As Glen Lambert has kindly pointed out, OS/010 issue 2 of June 1963 certainly, and perhaps the original drawing of late 1961, gives C5, which is within the circuit of the AC30/6, as 0.047uf.

The earliest version of OS/010 known at present, June 1963, first version - listed as (2) above.

The sheet for the AC30/6 from late 1961/early 1962 naturally gives the old WIMA Tropydur value 0.05uf:

Detail from the sheet for the AC30/6, late 1961/early 1962.

As 0.047uf is also the value given in diagrams for the AC30/6 drawn out in June 1963, it seems clear that JMI adjusted its drawings not only when changes to the circuit were required but also to keep them in line with the types of components being used - ie. the build.

Detail from a sheet for the AC30/6 drawn up in mid 1963 - printed by J. Elyea as sheet number 19 in his schematics portfolio.

Mullard mustard capacitors and WIMA Tropyfols came in 0.047uf not 0.05uf. The discrepancy makes no difference to the circuit. It was simply a case of employing the "nearest neighbour" available in the new brands/ranges that had been adopted.

More to follow.

19th January (2)

The page on has been updated and augmented with further material on the AC30/6. At least six iterations - it seems too much of a leap at present to call them "versions" - of the diagram for its circuit were produced: (1) the original of 1960 (no sheet number); (2) of the second half of 1961/early 1962 (no sheet number); (3) mid 1963 (no sheet number); (4) mid 1963 (designated A/026); and (5 and 6) September 1964 (designated OS/065 and A/026).

An expansion of the section on OS/010 - the circuit for JMI's add-on Top Boost unit - to follow. There were at least three iterations of that sheet.

19th January

A copy of the circuit diagram for the AC30/6 mentioned in yesterday's entry, and a shot of two 0.05mfd WIMA Tropydurs. In later diagrams the values of the 0.05 and 0.005mfd caps (noted throughout the sheet in view) were silently changed to 0.047 and 0.0047mfd, the closest values available in the newer brands/ranges adopted - WIMA Tropyfols, Mullard mustards, and so on.

Quite when the diagram for the AC30/6 became OS/065 is not clear at present. The earliest original sheets printed by Jim Elyea in his schematics portfolio (Numbers 19 and 20), both from mid 1963, have respectively a much simplified information panel giving the name of the model only, and A/026. It may be that the designation of the circuit as OS/065 came in the wake of the order from Thomas Organ in late August 1964. Putting the circuit diagrams in order will have been a necessary preliminary prior to despatch to the Thomas Service Center in Evanston.

The latest date generally given on the sheets designated OS/065 - in effect those that have circulated on the web for years (often with completely misleading filenames/captions) - is 11th September 1964.

Various pages on the site will need to be adjusted.

Click for a larger downloadable version.

WIMA Tropydurs, 0.05mfd

18th January

Recently come to light, a circuit diagram for the AC30/6 from the second half of 1961 / early-ish 1962. The values given for the smaller capacitors indicate that black WIMA Tropydurs were envisaged. No OS number is given for the sheet in its information panel. Below, a detail of the modifications list - "List of Changes".

This as it turns out is not the earliest circuit diagram to survive for the AC30/6, however. Thanks to James Kelly, it is clear that a "Pre-LOC" (pre "list of changes") sheet is still extant.

A good resolution scan of the whole of the diagram that has recently emerged will be made available shortly.

16th January

In mid to late 1964, the was merged with the to form the Domino Reverb piggy-back amplifier. JMI discontinued The Domino Super Reverb to make way for the new AC10 SRT.

The colour scheme for the new Domino Reverb, as for the other members of the Domino range, was green and silver. The circuit for the amp remained the same - four controls: Reverb, Volume, Vibrato speed, and a combined Tone and On/Off - only the format and livery changed.

Detail from the "Precision in Sound" newspaper-format catalogue printed in September 1964.

Detail of a new-style Domino Bass amplifier section to show the general scheme.

So far no examples of the new piggy-back Domino Reverb have come to light. However, a certain number of amps - or at least chassis - were evidently made. Below, a new-style Domino Reverb chassis in an AC10 speaker cabinet. The amp did the rounds on ebay for around a year before being bought in by a dealer and resold.

Controls are: Reverb, Volume, Vibrato, and combined Tone and On/Off.

The cut-out in the top of the cabinet seems to be fairly rough and ready.

15th January

A slightly hazy shot of the new AC10 Super Reverb Twin with slope-sided (trapezoid) amplifier section cabinet taken in the Jennings stand at the Russell Hotel Trade Fair in late August 1964.

The standee on top reads "AC10 SUPER REVERB TWIN" / "TOTAL WEIGHT ONLY 45 LBS". 45lbs is around 20kg. Note the full length handle on top, as on the new AC30 SRT.

Russell Hotel Trade Fair, late August, 1964.

First design for the AC30 SRT amplifier section.

14th January

The page on the has now been started - as ever more to follow. One of the consequences of gathering material on its circuit - most of it kindly supplied by Glen Lambert - is that the page on surviving will need to be re-cast - also to come soon.

Domino Super Reverb control panel

13th January

A portmanteau entry on the Laurie Jay Combo, Jennings, and Ampeg. In October 1962, Laurie Jay is presented as an endorser of Jennings guitars and amplifiers - matching black Phantoms and a Vox Transonic ("AC30 Transonic") with integrated tremolo. This is the earliest dated "real-world" (rather than studio or trade show) picture of the Transonic that has come to light so far. Jennings was surpassingly good at getting its equipment into the hands of bands featured in TV programmes.

October 1962.

By early 1963 however, Jay had evidently defected to Rose-Morris and Ampeg. The advert below is one of the first for Ampeg in the mainstream British music press.

January 1963. Pictured are a B15 bass amplifier and what appear to be two Reverberockets (sometimes called the "Reverb Rocket").

Although details of how the deal came to be struck remain to be clarified, it is clear that Rose-Morris had taken on distribution of Ampeg in the UK by the summer of 1962. A B15 and Reverberocket can be seen on the company's stand at the Russell Hotel Trade Fair in late August 1962

August 1962, Rose-Morris stand at the Russell Hotel Trade Fair, Ampeg B15 and Reverberocket centre foreground.

Dick Denney will, without a shadow of a doubt, have seen these amps. The Jennings stand - which he oversaw - was just a few along from Rose-Morris's. Quite what the specific steps were that led him to have the circuit of the Reverberocket drawn out as OS/026 in February 1963 are still anyone's guess. It does not seem unreasonable to think though that seed was sown at the Fair.

9th January

There is now a page on the circuit diagrams for the Vox AC10 and Domino Super Twin Reverb amplifiers - available here. This brings together amd harmonises various overlapping sets of notes posted earlier this year. Comments of a more technical nature on the circuit - or rather circuits - will be added in due course.

OS/026, "Issue 1" and its date, noted on the sheet top right.

7th January

Thanks to Eric, pictures of AC30 transistor Lightweight serial number 509. The sequence began at 500. Pics of serial number 505 to come in due course. The page on the model .

AC30L serial number 509. The amp is .

6th January (2)

Footswitches for the Domino Normal and Domino Reverb combos. The earliest type were a simple chamfered wooden block with the switch inset, as provided also with the AC2 (very rarely with the AC4 though, which normally had cast metal egg-shaped switches).

In early 1964 the Dominos were given a new type of stylish wedge-shaped footswitch, some white, some black, both versions apparently made of thick moulded plastic (bakelite?). These eventually gave way to the standard JMI egg-shaped switches.

AC2

Domino Normal

Domino Reverb

6th January

The three types of Domino control panel: blue initially, then black and white engraved trafolyte, followed by silk-screened [probably not anodised as previously stated] black and white.

In company with the Domino Bass illustrated in the "Precision in Sound" fold-out brochure of late 1963, the amp in the second picture has white plastic nuts on its input sockets - see the pic in the entry for 31st December, below.

Domino Standard serial number 1047.

Domino Standard serial number 1049.

Domino Standard serial number 1833.

5th January

A page has been started on the . The provision of reverb (a single spring unit) pushed the price of the amp £7 and 7 shillings over that of a standard (non-reverb) Domino combo: £26 and 5 shillings v. £18 and 18 shillings. Notes on the circuit will be added in due course.

Currently in preparation a page on the Domino Super Reverb Twin - "piggy-back" - amplifier, this to be linked to a page on the AC10 Super Reverb Twin. The two amps were built to the same circuit. Surplus Super Reverb Twin chassis - probably purchased incomplete - were also used post-JMI to create the factitious so-called "Mystery Amps" (not really a mystery unfortunately).

Below a detail from the earliest surviving version of the circuit diagram. [Updated A note on the sheet gives the date of "Issue 1" as 13th February, 1963]. The sheet will be posted in its entirety on one of the new pages. As noted earlier this year OS/026 was redrawn in early 1964 by Albert Hogben, JMI's principal amplifier circuit draughtsman from 1964 to 1966. A copy of that sheet was printed by Jim Elyea (in his "schematics" portfolio). Steer clear of OS/71 - a further version that has circulated on the web for many years. AH inadvertently introduced a colossal error.

A detail from OS/026, drawn by Mike Turner. Updated - a note on the sheet gives the date of "Issue 1" as 13th February, 1963.

4th January

There is now a page on the (both names were used), further material to be added in due course. A short page on the relatively short-lived Domino Reverb combo is next in line.

Detail from the JMI "Precision in Sound" fold-out catalogue of later 1963.

Added to the page on the Domino Bass, a note on the method adopted by JMI for the securing of the amplifier section to the speaker cabinet - chrome-plated brackets and thumbscrews. These were copied from Fender. JMI had been Fender's main distributor in the UK from early 1961 to the autumn of 1962.

A detail of the bracket and thumbscrew on a Domino Bass. JMI later used the arrangement in a modified form for the UL710 amplifier and cabinet set. Later still (in late 1966) a new format of bracket and thumbscrew was devised for the Vox Conqueror and Defiant sets.

3rd January

A page on the so-called "Mystery Amp" . Around a dozen are currently known. There are bound to be more floating around though. A grand total of none has a serial number plate. They are likely to have been made up from surplus parts purchased in late 1967 / 1968 at the JMI liquidation sales. No matter who made them - a group of smiler boys from South London seems probable - they are great sounding amps. The chassis is effectively an AC10 / Domino Super Reverb Twin.

Pages to come shortly on the two Domino combos: the Domino Normal and Domino Reverb.

2nd January

The page on the "Domino Bass" has now been started - . Serial numbers lie in the range 2000-5000. Whether this means that 3000 were made, 1963-1965, is unclear and perhaps unlikely. It may be that the sequence was shared with the "Domino Super Reverb Twin". The serial number plates of the two models were stamped by Jack Jennings with identifying designations, "RV" and "B" - primarily for record-keeping purposes (sales, potential returns for repair, and so on).

Surviving "Domino Normal" and "Domino Reverb" amplifiers were assigned numbers beginning at 1000 and apparently not stretching into the 2000s. Again, probably a shared sequence.

The upshot is that ub total just short of 4000 Dominos appear to have been made and sold from mid/late 1963 through to 1965.

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