With The Shadows and other British bands of the era playing for larger crowds in bigger rooms, it became instantly clear that the 15-watt Vox amps they were using were no match for the number of screaming fans in the audience who would overpower the volume of the guitars. After a chat with Dick Denney, the 4-input AC-30/4 was born.

These amps are basically two AC-15s in a slightly larger cabinet, with a second pair of EL84 power tubes and a second speaker. The AC-30/4 is quite rare, as it was produced for just under a single calendar year before the redesigned AC-30/6 Twin was introduced .