the upper valence covered in fawn Rexine, and the lower grille covered in brown diamond cloth. Ventilation was provided by three small brass vents on the top of the cabinet, and the TV-front's single suitcase type handle was replaced with three leather straps. Since the higher output AC30/4 shared its preamplifier design with the lower powered AC15, Vox discovered the high-gain EF86 tube was susceptible to microphonics, or even failure, when exposed to the increased vibration present in this uprated amp. Vox soon tired of the problem so to cure AC30/4 reliability issues caused by the troublesome EF86 preamp tube, in late 1960 Vox redesigned the preamp circuit, replaced the EF86 with an ECC83 (12AX7), and released this new design as the AC30/6. The AC30/6 was now an amp with three channels, each channel having two inputs. About this time, the "Top Boost" (or "Brilliance") feature became available as Vox's optional addition of a rear panel-mounted circuit that introduced an extra gain stage and tone controls for bass and treble (as opposed to the single "tone" control of earlier AC30s). The unit became so popular that its features were soon incorporated in newer AC30/6 models, and the controls moved from the rear panel to the control panel. Vox AC30/6 amplifiers from around 1963 had already implemented the top boost, and therefore had three tone controls. People began to refer to these amplifiers as AC30TBs. Later on, Vox also offered additional versions of the AC30 unit. In addition to the "Normal" version without the Top Boost, and the Top Boost version (which was a Normal version with the "Brilliance" unit added), Vox, with slight circuit modifications, created two more versions that were "voiced" in Brilliant (Treble), and Bass styles. Over the years many different AC30 models appeared but many consider the AC30 "Super Twin" to be the ultimate AC30, with a "trapezoid" shaped head and a separate speaker mounted on a trolley (see The Vox Story, Petersen & Denney 1993, p.39; see also the Vox showroom web site). To meet the demand of providing louder sound levels in live settings, the Vox AC50 was introduced as louder yet similar sounding "Super Twin" model, providing over 50 watts of power. And the infamous AC100 was produced shortly after which was the loudest of the Vox AC models ranging in 80-100 watts. In the late '60s Jennings drifted into financial problems and the