Vox AC30 Super Reverb Twins
Early amplifiers in "square-edged" cabinets.
Mid 1962 to later 1964 - copper then grey panels
Serial numbers from the high 5000s to new series 2500s
"Melody Maker" magazine, 12th May, 1962 - to date the earliest dated instance of the Super Reverb Twin.
Standard AC30 Super Twins (ie. without reverb), which were introduced in September 1961, can be found on this page.
So far as we can tell, the new Super Reverb/Twin/I (with one 2 x 12" speaker cabinet) and Super Reverb/Twin/II (with two 2 x 12" cabinets) were introduced in May 1962. Controls were on the back panel in a cut-out; reverb tray enclosure and driver transformer mounted on the underside of the amplifier's slider board. Early examples are scarce.
The controls on the back panel of AC30 Super Reverb Twin serial number 2803.
In order to avoid paying a license to use an existing reverb design (from Hammond, Accutronics, and so on), JMI came up with its own. In the first instance, a pair of springs in parallel, with phono cartridges - normally white ACOS units - at the ends to serve as transducers. The tray containing the springs was suspended in the reverb enclosure by rubber bands in order to isolate it as far as possible from external vibration - it worked (to a degree). ACOS cartridges remained in general use through to 1966, after which time red Sonotones came in. Later reverb tanks had only one spring. A schematic for an add-on reverb unit, to augment standard AC30s, was drawn up on 15th January 1965 - OS/075.
Above a reverb module and double spring tank removed from an AC30 SRT.
Details of a single-spring reverb tray from a later sloping-sided AC30 SRT. Note that the rubber band (first picture, top left) has perished and no longer extends across the width of the tray through the black rubber grommets to suspend (isolate) it within the enclosure. One can just see the details of the ACOS cartridge - Stereo, GP 71.
Note that at first the amplifier sections of AC30 SRTs had standard "square-edged" Super Twin cabinets. Later (in 1964), a trapezoidal cabinet with sloping sides came into being.
The new format AC30 Super Reverb Twin represented in the "Precision in Sound" newspaper format catalogue of late 1964. Note that the amplifier section has sloping sides. The chrome stands on top of the speaker cabinet were a pre-production try-out. Production amplifiers had standard full trolleys.
The first Super Reverb Twins had serial numbers in the high 5000s, and they were numbered in sequence with plain AC30 Twins and plain Super Twins through to around serial number 10000. Thereafter Super Twins and Super Reverb Twins were given a sequence of their own beginning at 2500.
Detail of a JMI invoice from 10th July 1962 for an AC30 Super Reverb Twin I.
If anyone knows of further early Super Reverb Twins that should be incorporated on this page, do let me know.
Old serial number sequence
High 5000s to 12000s
Serial number 6019B - currently in the UK
Existence noted on this page. The short description: "The covering is brown/fawn, speakers are Celestions, it has built-in spring reverb, and treble and bass switches are on the back (maybe not original). I got it for £20". The amp is in actual fact a Twin with factory added Reverb - see this page.
Serial number 7785 - currently in the UK
First version amplifier section (with straight sided box), first half of 1963. Both cabinets covered in basketweave vinyl. Thanks to Phil for the pic.
Serial number 8855 N - currently in the UK
Copper panel. Rectangular amplifier section box. Complete with original closed-back speaker cabinet and JMI speaker cable. Both cabinets covered in basketweave vinyl.
Serial number 10956 - currently in Denmark
Paired with a Fender (?) cabinet. The amplifier section is in excellent condition. Imported to Denmark early on by Europaisk Musik Import Co.. which was required by law to remove the voltage selector and fit ancillary fuses internally. Thanks to Rasmus for the pictures.
Serial number 10322 - currently in Germany
A Super Reverb Twin with added top boost (as serial number 2881 lower down this page). Originally sold by Servaas in The Hague - shop plaques on the two sections. Chassis assembled by Westrex; Albion transformers. The date code of the Radiospares capacitor in the preamp is "UK" = October 1963.
Serial number 11118 - currently in the USA
Basketweave vinyl; brass vents in the box. Given the Woden transformers, the chassis is likely to have been produced by Burndept. There is no sign of the red solder dye used by Westrex at any rate. The output transformer and choke have the date code code "AV" = January 1964. One of the blue Hunts bypass capacitors in the preamp has "IWI" = 13th week of 1963. Note that the serial number plate is headed "AMPLIFIER" rather than "VOX AMPLIFIER" as some were for a short period in the first half of 1964. The number itself is hand stamped and followed by "R" alone = "Reverb".
New serial number sequence
2500 to 5000
Serial number 2741 - currently in New Zealand
Super Reverb Twin serial number 2741
Chassis probably assembled in the second quarter of 1964, the reverb unit now removed and the control cut-out used for a Top Boost unit. Thanks to George for the pictures.
Serial number 2803 - currently in the UK
Assembled by Westrex under contract for Vox. A Super Reverb Twin without top boost. Copper panel; link voltage selector; Albion transformers. One of the potentiometers has the date code "AL" = January 1964. The blue Hunts capacitor in the preamp has the date code "T UI" = 46th week of 1963. The double pin corner protectors are later additions.
Serial number 2881 - currently in the UK
Thanks to Peter, pics of AC30 Super Reverb Twin serial number 2881 with added Top Boost. Brown grille cloth, grey panel. Probably produced in the third quarter of '64.
Serial number 3017 - currently in the USA
An early grey panel SRT with its original trolley, a "basket" on top wider than the parallel bars to hold the amp. The trolley's uprights are closer together than on trolleys produced in 1965. The amplifier has in-panel top boost.
Serial number 3225 - currently in the UK
Two pics only for the time being. Still copper panel, link voltage selector.
Serial number unknown - currently in Europe
Grey panel without top boost. The speaker cabinet still has its original rectangular Cannon XLR-3-32 socket. The amplifier cabinet has new-style black vents on top.
Serial number unknown
Black grille cloth; externally in excellent condition. The runner on the grille of the amplifier section survives "Super Reverb Twin".
On to the next page: Super Reverb Twins, 1965-1968.