Jennings' first successful product was the Univox, an early mains powered electronic keyboard with built-in valve amplifier and loudspeaker, similar to the Clavioline.
In 1956 Jennings was shown a prototype guitar amplifier made by Dick Denney, a big band guitarist and workmate from WWII.
Dick Denney received very little for his invention but continued to design from a workshop built in the garden of his council house in Erith, Kent.
The company was renamed Jennings Musical Industries or JMI, and in 1958 the 15-watt Vox AC15 amplifier was launched, and was popularized by The Shadows and other British rock 'n' roll musicians.
Jennings Electronic Industries operated for several years, making an updated and rebadged version of the AC30 along with other amplifiers, as well as a new range of organs.
[citation needed] In early days of the new JMI, a small number of 50W and 100W hand-wired heads were produced, as well as cabinets, to test the waters for a re-launch.
Giles had previously built amplifiers based on Jennings’ designs, which impressed Richard Harrison to such an extent that some prototype models were made.