The Vox AC30 Super Twin 2 - amplifier and two speaker cabinets
Late 1961 to 1963 - black and copper panels
Serial numbers in the high 4000s to the 10000s.
Flyer from autumn 1961 illustrating an AC30 Super Twin 2 set and Phantom guitar.
An overview of the early documents relating to the introduction of Super Twin range can be found on this page.
In many ways, the Super Twin II - a separate amplifier section with two closed-back speaker cabinets - is an astonishing thing, far ahead of its time. No other English manufacturer of amplifiers designed for use by guitarists and bassists produced anything remotely similar. Quite how many were made (and sold) by JMI is difficult to say. Given the price - 175 guineas in early 1962 is equivalent to around £3600 today - probably relatively few. Portability, or the difficulty thereof, will doubtless have been a factor too.
Detail from a JMI typescript pricelist, beginning of 1962.
By early 1963 the model had been phased out, the Super Twin Reverb II, which had been introduced in early 1962, taking its place as the most sophisticated Super Twin available as a standard set from JMI. The Super Twin Reverb II lasted through to 1967.
From late 1963, one could of course buy amplifier sections and speaker cabinets separately, so it is possible that players from time to time made their own versions. But those were not standard production sets.
Detail from the JMI pricelist of February 1964.
"Exchange and Mart", London edition, May 1968, the seller (in South Croydon) knows what he has. It is unusual to see the model listed in small ads or in shop ads for that matter.
May 1968
Outward appearance
Cabinets were issued in both beige and black pebble pattern covering early on; handles were of leather, one apiece for speaker cabinet and amplifier section. Injection moulded rubber handles came in at around serial number 7000. The picture at the head of this page shows the arrangement envisaged by JMI for the setup - amplifier section on the stand, speaker cabinets on the floor.
Amplifier sections normally had two metal XLR sockets (bought in from Geloso in Italy) on their rear back board. These were connected to the terminal block for the output transformer on the chassis of the amp - i.e. as the speaker would be in an AC30 Twin. A page on Geloso sockets and plugs can be found here.
Detail of the sockets on serial number 5002. The smaller jack was added later for the footswitch.
Wiring
In terms of impedances, the sockets will have been linked at factory to the 8 ohm tap on the speaker terminal block in the preamp in order to accommodate the two cabinets of 16 ohms apiece (two Celestion blues in each). If the player decided to use one cabinet on its own, JMI's expectation presumably was that the sockets should be linked into the 16 ohm tap - which involved taking the back panel off. It is fairly safe to assume that the owners of Super Twin II sets did not always do this. Whether the documentation supplied with the amps by Jennings laid down the law in fairly unequivocal terms is unknown at present.
Serial number 5002, the terminal block for speakers / sockets. Green (top) is 8 ohms; black (centre) is common; blue is 15/16 ohms.
Surviving examples
To date no Super Twin II set has come to light complete. However, a number do survive with one cab only, the second presumably having been sold or passed on separately at some point.
Further images of the amps below can be seen on the general page on early AC30 Super Twins. The pages on AC30s with serial numbers in the 5000s and 6000s, are here, and here.
If anyone knows of early Super Twin 2s that should be incorporated on this page, do let me know.
Rear of serial number 5002 (early 1962), the cellophane there temporarily to protect the plate. Further pictures of 5002 are linked on the main Super Twin index page.
Rear of serial number 5056 - No, not 5056 but a number in the 5600s or above - see the entry for 24th August 2025 on the Updates page. The arrangement arrived at for this amp makes better sense, sockets and wiring above the slider board.
Serial number in the 5800s, probably 5820 or 5830. Apparently factory-made on the back panel. The amplifier section cabinet has been pictured with two different chassis in place though, so care is needed when assessing this amp.
Chris Squire pictured c. 1967 with what may be an Super Twin 2 set from the first half of 1962:
