Vox AC30 website updates
November 2022
29th November
Some updates coming shortly. Just to note that details relating to AC50 speaker cabinets (some new findings) are currently being assembled here on the updates page of the AC50 website.
26th November
Just to cross an "i" and dot a "t", a detail of the plate of AC15 serial number 3745, the picture having decided to separate itself from the others (until now).
AC15 serial number 3745.
25th November
A note on JMI serial number plates in 1966, 1967 and early 1968, three different varieties.
(1) In early 1966, around serial number 20700, a new three-line plate comes in, the third line provided for "RATING" - power consumption in watts (not not audio power output). All details - model designation, serial number, and rating - are machine stamped. JMI introduced the new-style plate across its range of amplifiers.
(2) For a short time in the latter part of 1967, the two-line plate returns - around serial number 22750 to 22896. The serial number is generally hand-stamped, though the model designation - "AC30" - was evidently sometimes machine-stamped. One also finds in this range, an occasional three-line plate, also hand stamped. Hand stamping of the serial number is the key.
Serial number 22750, the lowest/earliest in a small batch of late two-line plates still with "VOX AMPLIFIER" at their head. This plate accompanied a stray back board sold last year.
(3) In very late 1967 / early 1968, a two-line plate with "AMPLIFIER" rather than "VOX AMPLIFIER" at its head was brought in - probably shortly after JMI had been placed in the hands of the official receiver. The earliest serial number known at present is 22976, the latest 23010.
24th November
Thanks to Norbert, pictures of AC30 serial number 15101T, third quarter of 1964, in really superb original condition.
AC30 serial number 15101T.
23rd November
The case of AC15 serial number 4851. Around October 2021, pictures emerged of the amp, a distinctive hole in its back panel, the amplifier chassis with a copper panel - which last is perfectly in line with the serial number and point in production. In the preamp, a couple of Hunts capacitors have visible date codes, one "HUH" = 26th week of 1962, another "YDH" = 8th week of 62, both also in order for this point in production.
AC15 serial number 4851. Note the hole in the upper back board.
The preamp of the amp as it was.
A month or so later, serial number 4851 was sold, but with an entirely different chassis and speaker in the cabinet - note the distinctive hole.
AC15 serial number 4851 again. The Celestion blue (replacing the one in the earlier set of images) is from mid 1961. RIC cone codes changed every month or so. "RIC 1 YG" also appears on a pair of speakers (from AC30/6 serial number 4606) with date codes "16FF" and "29FF" = 16th and 29th June, 1961. See this page.
We do not of course know in this instance anything of the "back story", though it may be possible ultimately to trace where the chassis with the copper panel went. If you are a prospective buyer of an early AC15 or AC30 (or even later ones come to that), be very, very careful. Sometimes the clue lies in the seller's blurb - things not said or hedged around (evasions), key elements not pictured, and so on.
22nd November
Thanks to Sid, pictures of AC15 serial number 4482. The chassis has Hunts caps with date codes in late 1960. The Celestion blue has the cone code "RIC 1 GY", which places it in late spring / early summer 1961. The serial number plate is of the type also found on AC15 serial number 4510 and some black panel AC30/6s (at this point too).
Chassis and box appear to have been together for a long time, though at this stage in production one would normally expect to find a split front rather than TV front. The pebble vinyl seems to be of type used on some AC30s in 1963; the bagging of the grille cloth suggests some sort of refitting.
AC15 serial number 4482, mid 1961.
20th November
As has long been known, Woden's longest standing client in the world of instrument amplification - really its only client of any significant length of standing in that world - was Jennings/Vox, 1962 to 1968.
Below, three Woden transformers in, and for, amplifiers not made by Vox. The first has already been illustrated - a Filmosound amp sold by Rank in the UK under license from Bell and Howell, perhaps produced for Rank by Westrex. The date codes of mains and output transformers are "AU" = January 1963.
The mains transformer at left is similar in general format to those produced for Vox but has two shrouds (top and bottom) rather than a single shroud at top and open winding wrapping at bootom.
The type of amp from which the the transformer with date code "CX" (March 1966), below, comes is unknown at present, possibly a hifi "home-build" unit.
Date code "CX" = March 1966.
19th November
Some pictures of a reverb unit from an AC30 Super Twin Reverb. The circuit in view is that of JMI sheet OS/075. The version below is from the Thomas Organ "Vox Amplifiers Service Manual" (first issue) and likely to have been drawn up anew for Thomas in January 1965. Reverb had been available since late 1962.
Later in 1965 JMI revised and simplified the circuit, designating the new sheet OS/75/R. A solid state reverb circuit was also developed, perhaps at the same time, for the Metal-Clad public address amplifiers - the "MC" range. This was still available as a built-in "extra" in 1967.
In the two valve circuits - OS/075 and OS/75/R - reverb is only assignable (separately) to the Normal Channel (NORM) and the Vib-Trem Channel (EFF).
The version of OS/075 embodied in the Thomas Organ "Vox Amplifiers Service Manual" of early 1967. The date of redaction of the sheet is 15th January 1965.
10th November (2)
The speakers below are likely to be 10" USA-made CTS alnico drivers, used in the mid-1960s by numerous American manufacturers, including Magnavox.
10th November
Original context unknown, a couple of Fanes or Elacs [not so, see the entry above] in Jennings blue, horseshoe magnets with non-standard "VOX" labels. Probably 10", provision on the frames for mounting a transformer. Note that the solder terminals are facing downwards in relation to the labels, so use in a combo amplifier is unlikely. Use in a Line Source 40 public address column unit seems unlikely too as the terminals on the speakers fitted in those were normally in line with the logo horizontally.
6th November
Five more entries from the Celestion "T" book, early 1964:
T1005: - G12 alnico sprayed Jennings blue.
T1044: - G12 alnico 8ohm. Cone assembly for T530.
T1059: - G12 Ceramic. 8ohm. 1" voice coil. Jennings. 3.25x550, 75cps resonance.
T1060: - G12C Ceramic. 8ohm. As T1059 except rubber treated with 749/003 cone.
T1066: - G12 Ceramic. 4ohm. Fitted with Jennings cone assembly, coil 63 turns, 33swg wire, sprayed silver.
In company with T1141 and T1213 (mentioned yesterday), T1044 is probably a component part that could be purchased by specialist repair shops.
T1005, T1059, T1060 and T1066: - if these were actually produced in any number, they are certainly not common today.
T1005 may not have been for Jennings at all, even though the frame was to be finished in the blue originally selected by Tom for the T530, T900, T1022, and so on. The very specific mention of the cone assembly in the entry for the T1066 is intriguing, though again not decisive. Obviously the "Jennings cone" was something distinctive in the Celestion specification books, but without knowing more, the question of whether Jennings was the intended recipient of the T1066 has to be left open.
T1059 and T1060 on the other hand, both with ceramic rather than alnico magnets, were certainly designed/intended for JMI. But what for? A revamping of the AC30 in early 1964, or simply something experimental? Another possibility of course is that the T1059 and T1060 were actually for Jennings and Thomas organs. Tom had taken on the distribution of Thomas products in the UK in the summer of 1963. Thomas sent its organs to Dartford Road as parts to be assembled. It would hardly be worth sending speakers, which could easily be ordered from British suppliers.
Brian Harding's overview of the Celestion T-book is invaluable.
5th November
Some random material on speakers. First, below, a relatively late blue with a RIC cone - 21st June 1962 - though this is unlikely to be the latest. A pair in AC30 serial number 6529 have RIC 2 TO and RIC 2 TP, though the date codes are unknown. Other examples can be found on this page:
RIC 1 KJ.
Next, two T1088s from early 1966 or later (solder terminals on a discrete board). These have "444" cones. Just to signal their presence/existence. Perhaps they are recones. Most T1088s have cones stamped H1777 or 102 003.
In 1964, Celestion recorded in its register - the "T Book" - various recone kits for speakers supplied to Jennings. Among these were:
T1117: - Recone kit for T530 / T1088.
T1213: - Recone kit for the Vox 12" T1088.
It is likely that the latter was actually for Thomas Organ in the USA. Presumably in the UK, specialist shops could simply ring up Jennings or Celestion and order cones and voice coils to be sent out for dead blues or silvers. Such kits were never listed in general JMI pricelists.
Updates for October and November 2020.