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The Amps & Cabs • Class A-30 – based on a 1967 Vox AC-30 Top Boost
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Class A-30 – based on a 1967 Vox AC-30 Top Boost
Music was changing in the early ’60s and guitarists were asking for more brilliance &
twang. So the Jennings Company, makers of Vox amps, decided to add Treble and Bass
controls (and an extra 12AX7 gain stage, incidentally) in addition to the Treble Cut
knob it already had (which in actuality was a sliding bandpass filter); this additional
circuit became known as Top Boost.
The AC 30 with Top Boost was the amp made famous by many British invasion bands.
Much of the unique character of the Vox sound can be attributed to the Class A
circuitry—Class A amps overdrive in a very different way than Class AB. Brian May of
Queen, Mike Campbell of Tom Petty’s Heartbreakers, and The Edge of U2 have all
used classic AC 30s to make their music. Although often played fairly clean, a cranked
AC 30 has a great saturated lead tone, a la Brian May on early Queen albums.
On this Amp Model, Duoverb’s Mid control acts like the original Cut knob on the AC
30. We also turned the Bass and Treble controls around, unlike the design of the Top
Boost electronics, which has the bass and treble turned all the way down when the knob
was all the way up. Go figure.
The Cabinet Model is based on the Vox and its two 12-inch Celestion Bulldogs.
All product names are trademarks of their respective owners, which are in no way
associated or affiliated with Line 6. These product names, descriptions and images
are provided for the sole purpose of identifying the specific products that were
studied during Line 6’s sound model development.
Duet Manual Page 6 Tuesday, October 1, 2002 9:36 PM