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Vox AC30 website updates

February 2024

29th February

The phenonomen of "blueprinting". This really caught hold in the late 1990s. Where it "came" from is hard to say. The process, such as it was, effectively involved replacing almost every original component in a vintage amp with a modern equivalent bought from one of the large electronic parts distributors - Mouser and Digikey in the USA, Farnell and RS Components in the UK.

The result: - numbers of AC30s (and other amps) with few original resistors and capacitors remaining. The craze was not limited only to hobbyists. Techs and repair businesses often subscribed to the "methodology", which went something like this: (1) most original components were, 30 and 40 years on, well out of spec., and (2) the only way to bring an amp back to proper order and make it sound - in the case of the AC30 - "as Dick Denney had intended" was to rebuild it anew with components that were tightly in line with the values specified in the circuit diagrams.

One flaw of course is that most of the diagrams put into circulation by JMI were neither "blueprints" nor "build sheets", having in the main been drawn up after the event - occasionally with colossal errors - to help / guide repairmen. Build sheets are necessarily a completely different thing. A few have survived here and there, but generally not many.

The other flaw is that for most people (increasingly) the desirability of a vintage amp that has been completely redone in such a way - ugly yellow polypropylene caps, shiny bright metal oxide resistors, and so on - is severely diminished. Naturally, for the person doing the "blueprinting", for whom the rebuilding of an amp was often a learning experience (or retirement project), that could not matter less. The chief importance - and selling point - in their mind was that the amp had been "blueprinted".

Akin to "blueprinting" is "shotgunning" - replacing everything in lieu of fault finding, the feeling being that it is better in the long run to replace everything wholesale than to spend time chasing down a problem that is perhaps intermittent, elusive, or beyond the means of the hobbyist repairer to isolate. The end result of course was the same - an amp full of new components - the only difference being that one was advocated as a "methodology", the other a form of repair "of last resort".

Those who promoted "blueprinting" were often accused of being "fiddle fingers", incapable of leaving anything alone, filling their time with pointless "upgrades", etc. Most of that is fortunately a thing of the past now.

22nd February (3)

Just to note that the back-board pictured two entries below was, after recovering, replaced on the cabinet with the runner directly under the lip of the chassis. One can tell by the mark left by the slider board.

22nd February (2)

A couple of documents relating to the "Return of Vox" to the U.S.A. in 1980/1981. The NAMM show mentioned in the newsletter was the "Winter Music and Sound Market" in Anaheim, California, 6th-8th February, 1981 [corrected]. During the 1970s Dallas/CBS Arbiter had concentrated mainly on UK and European sales, so too Rose Morris - initially at least - following its acquistion of the Vox catalogue in 1978.

The "vintage" Vox amps making their way to the U.S.A during this period - often by the crate and container - evidently went some way to satisfying the "need" for "British Vox", and some good collections resulted. Old valve amps could be had for next to nothing in shops in the big cities in the UK. The "pile them high and stack them deep" merchants who bought these amps up made killings selling to America in the 1980s and 1990s - almost every AC30 a "1962" or "1963" of course. Those were the days. But there was still a need for the new.

The "Vox Advocates" were a group formed by Charles Forssi in the late 1970s to promote the virtues of Vox equipment, and to press for the return of new production amps to the US market. The group's newletters provided info on the new models, notes on the history of older amps, and adverts for "new old stock" Thomas Organ amps (for instance). There were sellers also of "new old stock" Vox organ components - the "American Organ Parts" company for instance.

Letter from T.S. Hull of Vox to John Tashjian. The Rose Morris buildings on Gordon House Road can be seen here. It is not known at present what "L.A.W. Ltd" in Worcester, MA, was.

The front page of the first bulletin issued by the "Vox Advocates".

By the summer of 1981, Rose Morris had its US exports in order. "Allstate Music Supply Company" in North Carolina became the first major Vox distributor in the country - see the foot of this page.

22nd February

A detail from a further early split-front cabinet (belonging to an AC30/4 serial number unknown) showing the runner on the inner face of its upper back-board. See the entry below for 20th February. The cabinet was recovered fairly early on in its life - the centre carrying handle was reinstated, but the side handles were left out and no fixing holes made for them in the covering.

It seems likely that the early split-front cabs were produced by P.A. Glock Limited in Crayford, a mile or so up the road from the Dartford Road factory - but that remains to be determined more solidly.

The page on Vox AC30 cabinets has been updated with a note on early upper back boards.

AC30/4, serial number unknown. The chassis had Hunts capacitors with late September 1960 date codes, though Hunts caps it has to be said were often months old by the time they came to be used.

21th February (2)

Thanks to Baz, a picture of his TV Front AC30/4 Twin, serial number 4241, bought second-hand in Watford in 1965 for £60, sold later on. The receipt for its purchase still survives. Baz is sitting on the amp.

The pages on the single speaker AC30 and TV Front AC30 Twins will be updated shortly.

AC30 serial number 4241.

21th February

Coming shortly, a page on the surviving AC30s that can be dated with some degree of confidence.

One example is AC30 Twin serial number 6758 currently in California - chassis with component date codes from January 1963 (pots and filter caps), therefore assembled in February (or perhaps even March 1963); Celestion blues with March 1963 codes (for their manufacture). Speakers, which generally have later date codes than components in chassis, could sit in store for as much as two months before use. Remember too that there might be some delay before a finished unit could be tested and given a serial number. In the case of serial numnber 6758, we are probably looking at an AC30 that is unlikely to have have been ready for use before late spring / early summer 1963. Prior to that the constituent parts were obviously simply constituent parts in store, unusable and useless without final assembly

Serial number 6758. Chassis assembled by Westrex. Still a good straight amp, thankfully free from the attentions of fiddle fingers over the decades. "You have to change the capacitors and resistors, because if you don't....!"

The general procedure through to 1964 was that when the time came for amps to be made up, the various elements were brought from store and assembled into complete working units (in cabinets) on the benches in 115 Dartford Road. The assembled amp would then put to one side to await testing. Once tested, the AC30 would be passed to the Despatch Department, where a serial number plate would be hand-stamped and affixed, and the details logged by Jack Jennings (Tom's brother): the date, number, model of amp, destination/recipient. That at least was the norm as reported by Rodney Angell, who worked as an amp tester from 1960 to 1964.

With the opening of the new Works in Erith in late 1964, things changed however. Bare chassis evidently sat around for longer, and machine-stamped serial number plates were clearly sometimes affixed to boxes before any chassis had been allocated. The disruption seems to have affected AC30 Super Twins and AC50s the most. For a time, amps were sent into the outside world from both factories (Dartford and Erith).

115 Dartford Road, probably July 1964. Final assembly of various models of amp. Far left, the testing rooms.

Early 1965, the testing rooms seen front on.

20th February

Thanks again to Dennis, pictures of the rear (internal) face of the upper back-board of AC30 serial number 4426 - principally to show the runner. At first sight, one would think that this had been provided to give secondary support to the slider board. But no, being 3/8" above the board's lower edge it simply serves to add rigidity. The slider board sits 1 7/8" above the runner's top edge.

The runner measures 24" long x 1/2" wide x 3/16" deep - ie. its outer face stands proud of the board by 3/16", and its ends are 1" from the board's left and right sides. The board is 26" wide.

Quite whether all early split-front cabinets were provided with such runners is unknown. They had certainly been phased out by late 1961 / early 1962 - ie. the advent of chassis with copper panels. The rear of serial number 4988's upper board is plain and always was.

18th February

Thanks to Dennis, pics of an interesting AC30. The cabinet and serial number plate are from Spring 1961. The chassis, which dates from autumn 1964, was incorporated at some point in the late 1960s. The original, which will have had a black panel, no longer survives, or is at least is no longer identifiable.

In terms of other additions, the speakers are relatively recent Celestions; the grille cloth has been renewed (with original 1960s cloth), along with the gold strip, logo, white piping, and handles.

The strongest sense is that the blue/grey covering is original. There are no signs anywhere of any older vinyl.

AC30 serial number 4426N.

11th February

Thanks to Jerry, a shot of the chassis of a first circuit AC1/15 probably from the third quarter of 1959, serial number in the high 3600s / low 3700s. The cabinet with its original Celestion B025 speaker also survives.

10th February

Some notes on the upper chassis of TV Front single-speaker AC30s, later 1959 to autumn 1960. The "Types" outlined below are fairly general in nature - within them, chassis could evidently be populated and fitted out differently:

Type 1

Re-purposed AC15 chassis (as Jim Elyea noted): choke and mains transformer removed, an upright output transformer added; EL34s close together; the Vibravox circuit housed in three cans potted with araldite.

Early, no serial number. Pic. from J. Elyea, p. 375.

Serial number 4041. Pic. from J. Elyea, p. 374.

Type 2

Based on the AC15 chassis, but specifically made for the AC30. A "lay-down" output transformer occupied the cut-out, still the provision for a capacitor to its left, no transformer or choke fixing points in the centre of the chassis though. EL34s spaced further apart; Vibravox cans three-in-a-row.

Serial number 4047.

Type 3

Chassis purpose-made for the AC30. No cut-out for a capacitor by the output transformer, EL34s spaced further apart; the three Vibravox cans here in staggered formation.

Serial number unknown.

Type 4

As above, chassis purpose-made for the AC30. No cut-out for a capacitor by the output transformer. The Vibravox circuit now concealed in a "doghouse", the idea probably copied from the Fender amps that Jennings had begun distributing in the UK.

Serial number 4060 (?) - white trafolyte control panel. Pic. from J. Elyea, p. 374. On p. 187 he indicates that serial number 4060 has a trafolyte panel.

Serial number 4158

As with other Jennings amplifiers, it clearly took a little while for production to reach a settled form - possibly as many as fifty or so amps. Thereafter things become more consistent - "more" necessarily being a relative term in this instance.

If serial numbers did indeed start at 4000, then around 160-200 single-speaker AC30s are likely to have been made ready for sale from later 1959 through to autumn / early winter 1960, the latest overlapping with the new TV Front twin speaker amps. Jim's note of a single speaker amp with serial number 4192 on p. 186 is likely to be a printer's error for 4102, which is recorded as being the latest he knew (on p. 378). That does not mean, however, that there never was a TV Front single speaker AC30 with that number.

The earliest genuine TV Front AC30 Twins known at present have numbers in the low 4200s. A starting point in the higher 4100s is likely though.

9th February

Thanks to Peter, pics of a late single speaker AC30, probably July-ish 1960. On the upper chassis, a "doghouse" containing the Vibravox circuitry, potted in araldite to prevent copying by other manufacturers.

In earlier AC30s (and AC15s), the circuitry was concealed in cans (masquerading as capacitors).

Below, the upper chassis of an earlier single speaker AC30 with a staggered arrangement of cans. Normally early on one finds the cans in a single row of three. In the amp pictured, the circuit could evidently be unplugged when required. [12/02/2024: preceding lines adjusted - the form of the amp's chassis indicates that it is likely to be later, not earlier than those fitted with a single row of cans - see the entry above for 10th Feb.]

The reason for the move from cans to a single "doghouse"? Probably a "lift" from Fender. In early 1960, JMI became the main (though not exclusive) distributor of Fender amps in the UK. Below, the venerable chassis of a Fender Twin from 1958/1959, its "doghouse" containing the main filter capacitors.