The Vox Cooltron Over The Top Boost is an overdrive pedal built around the Top Boost channel of the Vox AC30, the part of that amp responsible for its treble-forward, gain-on-top voice. Vox billed it as being able to "blast your tone over the edge and back"1. It belongs to Vox's Cooltron family, a line of pedals that put real valves in a stompbox by running them at very low voltages, a method known as "starvation"1.
An AC30 channel in a starved-valve pedal
The Top Boost channel has a long history on the AC30. As Guitar World's Huw Price tells it, Vox eventually relented and developed a Top Boost version of the AC30, and also marketed retrofit modules for earlier amps that opened up the treble and increased gain2. The Over The Top Boost takes that channel as its starting point and puts it on a pedalboard.
What makes the Cooltron approach different from most overdrive pedals is the valves. Rather than simulating tube behavior with diodes or op-amps, the pedal uses actual valves run at very low voltages. MusicRadar's review notes that this delivers the valve character "but without the usual problems of biasing and, er, valve death!"1. In other words, the design aims to sidestep the maintenance and biasing concerns that normally come with tubes.
"The valves in this pedal are designed to run at very low voltages (a method known as 'starvation')."
The controls and interactive EQ
The pedal carries the control set you would expect from a boost and overdrive pedal, with an EQ section that behaves in a distinctive way1.
| Control | What it does |
|---|---|
| Volume | Sets output level, part of the overdrive flexibility1 |
| Gain | Drives the pedal from clean push to over the edge1 |
| Bass | Low frequency control, interactive with treble in standard mode1 |
| Treble | High frequency control, interactive with bass in standard mode1 |
The EQ is the interesting part. In standard mode, the bass and treble controls are interactive: tweaking the treble also affects lower frequency characteristics, and vice versa. MusicRadar's reviewer found that this "Powerful EQ circuitry makes for great tonal flexibility"1, giving the pedal more shaping range than the simple tone control found on many drives.
The pedal ships with four AA batteries but no power adaptor. A 9V DC adaptor must be bought separately if you want to run it off mains power1.
Where it sits in the Vox range
The Over The Top Boost was one of several drives in the Cooltron family, which shared the same rugged design language of tough steel casings, retro chickenhead knobs and a mirror finish1. Vox has since explored valve-flavored pedals in other directions, including the Nutube-based Valvenergy series such as the Vox Silk Drive and Vox Fuel Injector, and other Cooltron-era drives like the Vox Cooltron Big Ben Overdrive and Vox Straight 6 Drive remain part of the maker's pedal history.
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Questions
Does the Vox Cooltron overdrive have real tubes in it?
Yes. The Cooltron Over The Top Boost is a valve-powered analog design, with the valves run at very low voltages, a method known as starvation. According to MusicRadar, this lets the valves work without the usual problems of biasing and valve death, so you get tube character in a pedal format without the maintenance headaches of a tube amp.
Does the Cooltron Over The Top Boost come with a power supply?
No. MusicRadar notes that the pedal can be powered with either four AA batteries, which are supplied, or a 9V DC adaptor, which is not supplied. If you want to run it from a mains adaptor, you will need to provide your own.
How long do tubes last in a Vox Cooltron pedal?
The published review does not give a tube life figure. What it does say is that the starved-valve design runs the valves at very low voltages without the usual problems of biasing and valve death, which is the design's answer to the question of tube wear in a pedal.
Does the Cooltron sound like a Vox AC30?
It is based on the Top Boost channel of the Vox AC30, the channel Vox developed to open up the treble and increase gain on the original amp. MusicRadar's review describes powerful EQ circuitry that makes for great tonal flexibility, and Vox billed the pedal as able to blast your tone over the edge and back.
Sources (2)
- Vox Cooltron Over The Top review, MusicRadar, 2008-01-29
- Boost pedals: the history of the stompbox that supercharged the sound of rock 'n' roll, Guitar World, 2023-07-26
