AC10 Super Reverb Twin
Early 1963 to 1965
1st February, 1963, the earliest dated advert for the AC10 SRT known at present.
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Introduction
During the course of 1963, two circuit diagrams were drawn up for the AC10 Super Reverb Twin - OS/026 version 1 (13th February 1963) and version 2 (30th December 1963) - see this page for further details. As it turned out, neither was followed. Instead, JMI used a standard AC10 chassis (circuit diagram OS/008) paired with the "add-on" reverb unit - controls on the back panel - initially designed for the AC30.
OS/026, "Issue 1" and its date noted on the sheet, top right.
Rear of an AC10 SRT amplifier section from mid 1964 to show the add-on Reverb controls on its back panel. Underneath the slider board, the metal enclosure for the reverb springs.
The majority of chassis were produced under contract for JMI by Triumph Electronics in Purley and sent in batches to Dartford Road, where they were given boxes and speaker cabinets.
Speaker cabinets were closed back - termed by JMI "pressurised" - and from 1963 through to mid 1964 fitted with two Elac 10" speakers sprayed Jennings blue, model 10N/81, 15/16 ohms apiece, wired in parallel for a total impedance of around 8 ohms. Later cabinets were fitted with silver Elacs. The change-over from one to the other lagged behind AC10 Twins by a good number of months.
Below, thanks to Steve, a shot of something not often seen - the interior of a closed back AC10 Super Reverb Twin speaker cabinet, the wiring original (note the insulated staples) up to the added terminal block. The speakers are Elac 10N/85s. In company with AC30 Super Twin cabinets, the back panel has a thick inner board of birch ply.
Whether the wiring commonly ran along the foot of AC10 SRT cabs is not known. No parallels have come to light so far where AC30 Super Twins are concerned. A similar approach was taken later on though in a batch of AC50 Super Twin cabs.
Speaker cabinet of an AC10 SRT, second half of 1964, serial number in the 1400s or 1500s.
Through to mid 1964, AC10 SRTs were issued with serial numbers in the same sequence as standard Twins - numbers in the 4000s from early 1963 to early 1964; numbers in the 1000s from early to later 1964. The change in sequence corresponded with the move to new thicker-edged cabinets.
In mid to late 1964 JMI revised the AC10 SRT, the two major changes being a move to the circuit adopted for the Domino Super Reverb Twin in early 1964 (as expressed in JMI circuit diagram OS/026, versions 3 and 4), and a new type of amplifier section with sloping sides, sometimes termed "trapezoid", or in short-hand "trap head". This new "trap head" Super Reverb Twin was shown in public for the first time at the Russell Hotel Trade Fair of late August 1964. See the photo lower down this page.
The chassis of these later Super Reverb Twins were produced by Westrex rather than Triumph.
New-style AC10 SRT of late 1964 with slope-sided amplifier section. The dimensions of the speaker cabinet remained the same as before - 24" x 18" x 9", as given in the JMI dealer catalogue of 1964/1965.
So far as one can tell the AC10 SRT of late 1964 sold better in Europe and America than it did in the UK. Quite how many were exported to the Thomas Organ Company in the wake of the "Million Dollar Deal" is unknown, but evidently enough to warrant the creation of a swivel trolley for the two sections along the lines of the trolleys produced for AC30 Super Twins.
Switches
In common with other models of AC10, AC10 Super Reverb Twins were supplied with a simple footswitch, its lead "hard wired" (soldered) to the chassis, to switch the tremolo in and out. Reverb was activated by the controls on the back panel alone.
In mid 1964, JMI seems to have adopted - or at least experimented with - a different approach. At least one new-style AC10 SRT has a DIN socket for a removable switch (plug in and unplug as required), an arrangement also envisaged for the slope-sided AC30 Super Twin and Super Reverb Twin, though so far as one can tell at present not used during production. The plan may have been to make both tremolo and reverb switchable via the footswitch.
Detail of an AC10 SRT, one evidently sold in the UK.
From a series of photos submitted to the old Patent Office by JMI, 28th August, 1964. The metal brackets supporting the amplifier section were illustrated in the "Vox: Precision in Sound" newspaper-format catalogue of September '64.
The socket was also used for a time on later Vox Domino Reverb amplifiers:
Vox Domino Reverb serial number 3329.
In 1966, JMI adopted DINs in a more systematic way for the tri-function footswitches supplied with the 7-series amps, and a little later, for the fully solid state range.
1) Serial numbers in the 4000s - 1963 and early 1964
Thin-edged cabinets, rectangular amplifier section cabinets - part of the existing sequence of AC10 Twins. Amplifier chassis largely - note the qualification - in line with OS/008 with some precursor of OS/075 for the Reverb. The versions that we have of OS/075 are all late (from 1965).
Detail from "The Shadows Modern Electric Guitar Tutor", 1963 edition.
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Amplifier section only. Advertised by the infamous Marcus Hardy way back when (late 1990s), currently in Holland. The sockets added in front of the reverb tank can be seen in Hardy's ancient but legible pictures.
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An early thin-edged AC10 SRT speaker cabinet
An early AC10 SRT speaker cabinet that came up for sale a few years ago, original blue Elac speakers present but disconnected.
2) Serial numbers in the 1000s - early to later 1964
Thick-edged cabinets, rectangular amplifier section cabinets - part of the existing sequence of later AC10 Twins. Circuit diagrams OS/008 and a version of OS/075, as above.
Detail from the dealer catalogue of 1964.
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Serial number 1354
An AC10 Super Reverb Twin, amplifier section only, no mention of the model on the plate though. In the preamp, a "Fender" sticker.
3) Serial numbers in the 3000s - late 1964 into 1965
Slope-sided amplifier section cabinets, chassis assembled by Westrex for JMI. Shown in public for the first time at the Russell Hotel Trade Fair of August 1964. Exported to Europe, and to America for a brief time. The AC10 SRT appears as the "V-1-4" in the Thomas Organ pricelist of April 1965 but not thereafter. Circuit diagram OS/026, borrowed from the Domino Super Reverb Twin, versions of 1964 - see this page.
Detail from a photo taken at the Russell Hotel Fair, late August 1964. On the standee on top of the amp: "AC10 SUPER REVERB TWIN / TOTAL WEIGHT ONLY 45lbs".
All known AC10 Super Reverb Twins have machine-stamped serial number plates. The designation of the model is "AC10/T SRV". The designation of the plain (non-Reverb) Twin at this point was "AC10/T".
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Probably the most famous AC10 Super Reverb Twin - the one used on the Doug and Pat Show. Plenty of videos on Youtube, the shots below from their website.
Serial number 3272
"AC10/T SRV" - "S" in the top panel of the plate "RV" in the lower. The "T" for "Twin" was also introduced on plain (non-Reverb) Twins - see this page.
Serial number 3286
Serial number 3304