Vox reverb spring assemblies
Early 1962 to 1968
In progress, October 2025
The earliest dated advert for the Vox stand-alone Echo-Reverb unit currently known, early April 1962.
Below, an overview of the different types of JMI spring reverb assembly, 1962 to 1964 (for the time being).
Early portable reverb unit, beige/fawn covering. Double lines of springs joined in the middle. The white cartridges, hidden by metal shrouds, were made by ACOS.
The arrangement illustrated above was also fitted in AC30 Super Reverb Twins and AC10 Super Twin Reverbs through to the end of 1963 (and on into 1964).
Assembly and back panel control module from an AC30.
The assemblies were normally suspended by elastic bands in a metal enclosure fixed to the underside of the slider board:
Enclosure and assembly removed from an early AC30 SRT, one of the lines of springs subsequently removed leaving the centre post.
The ACOS GP71 cartridges in the assembly of an AC30 SRT from mid 1963 (serial number in the 8000s). Thanks to Magne for the picture.
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.
By mid/late 1964, JMI moved to single line spring assemblies (normally formed of one or more springs linked together), presumably to save money. Below, one from an AC30 (top), the other from a Domino Super Reverb Twin or slope-sided AC10 SRT (later 1964 and early 1965).
Below, details of slope-sided AC30 SRT serial number 5031, single spring assembly under the slider board (still the conventional position):
Above, AC30 SRT serial number 5031.
Prior to the adoption of the red Sonotone cartridge in 1966 for the 7-series and fully solid state ranges of amps, one sometimes finds a black type, maker currently unknown.
Late Vox Domino SRT. Such cartridges are also found in late portable Reverb units.
1966 to 1968
In late 1966, during production of the 7-series amplifiers, JMI moved (as mentioned above) from the white ACOS GP71 cartridges to red Sonotone 2T. Preamps and reverb circuits were driven by transistors rather than valves. Design is likely to have begun in mid 1965. Reverb was offered from late 1965 - price 10 shillings - for the all-transistor preamps of JMI's MC100/6 and 150/6 public address amplifiers.
Assembly with Sonotone cartridges, from an early solid state amplifier.