Rothwell Audio Tornado overdrive
The Tornado is a class A, single-ended
overdrive using JFETs throughout. The close similarity between the
electronic characteristics of JFETs and valves allows the Tornado to be
effectively a pre-amp in the classic guitar amp format, but implemented
in miniature and running from only 9 volts instead of the 2 or 3 hundred
volts required in a valve guitar amp. The result is an overdriven sound
that is much closer to that of an amp rather than a typical pedal but
with pedal convenience.
The control layout of volume, gain and tone
looks familiar enough but the addition of the shift button widens the
tonal palette. The shift button alters the response of the tone control,
shifting the mid-range content and altering the turnover frequency so
that both vintage and modern sounds can be produced.
The gain control
is also more sophisticated than it first appears. At the bottom end of
its range the sound is clean and with a full bass response, but but has
enough signal level to act as a clean boost. As the gain is increased
the bass is gradually cut (pre distortion) to maintain a tight and
responsive bottom end as distortion increases. At full gain the
distortion is thick and saturated and sounds weighty in the bass without
ever being bloated. The asymmetrical way in which JFETs overload - just
like valves operated in class A - produces a natural spongy
compression, and a source follower is used before the tonestack (just
like many rock oriented amps use a cathode follower before their
tonestack) to produce a biting edge to the sound.
Overall, the
Tornado produces a range of classic and modern rock sounds with aplomb
and has an engaging natural compression to it (rather than the sterile,
flat compression of many pedals).
Current drain of the pedal is very
modest - only 2.6mA when bypassed - so long battery life can be
expected, but a high quality chassis mounted 2.1mm centre negative DC
power socket is provided to allow the Tornado to be powered from an
external 9 volt power supply.

