A tube in a pedal? Pretty cool.

Introducing the COOLTRON series of effect pedals, three very special stompboxes that use a 12AU7 preamp-type tube at low voltage to deliver the kind of tone that, until now, would have been impossible to achieve in a battery-powered pedal.

Demo

Bulldog Distortion

With dual channels - each with its own Gain and Volume controls - and growling tube tone, the VOX Bulldog Distortion pedal adds extra bite to your fret burning maneuvers. Gain 1 dishes out vintage distortion while Gain 2 packs a more modern, aggressive sound with slightly scooped mids. Both are adjustable from subtle to completely over the top. A Bass control adds extra low end thump at extreme settings and a warm, round mellowness at lower settings. And with the Gain 2 Voice control you can independently tailor the second channel's hell-raising tone. A Treble control will take your sound from a biting attack at one extreme to smooth and liquid at the other. The Bulldog also is equipped with true bypass.

Want to know how it all works?

Normally, tubes are used at high voltages and this restricts their use in battery-powered devices such as guitar effects pedals. Historically, attempts have been made to use tubes at low voltages in what has been dubbed “starvation” mode, but these circuits don't allow the tube to function in an acceptable manner. The tube simply cannot be biased to a satisfactory operating condition. Plus, the necessary heater (filament) current is too high to deliver acceptable battery life. Imagine how annoying it would be to have to change batteries every ten minutes during a gig!

Here's what makes the COOLTRON system tick. The COOLTRON circuit basically operates by using two very special signal paths. The first is the “servo circuit,” which provides the right conditions between the plate of the tube and the grid. This achieves controllable, stable parameters for the tube and provides the correct operating conditions for the tube to function as it would if run at a higher voltage. The second circuit is a patented power supply that provides a low voltage, low current supply to the heater elements in the tube. Since the tube is now running at such a reduced supply level, the anode current is much smaller than normal. This means that the amount of heat required at the cathode to achieve sufficient cathode current emission is much smaller - hence the ability to run the heaters at a lower level and for COOLTRON pedals to run for 20 hours on 4 x AA batteries!

The COOLTRON system provides true tube sonic performance at very low voltage and at reduced heater current - ideal for inclusion into guitar effects pedals. COOLTRON guitar effects pedals offer valuable tube type sonic performance.

Specifications:

• Bulldog Distortion controls - Gain 1, Volume 1, Gain 2, Volume 2, Bass, Treble, Gain 2 Voice, Gain1/Gain2 Switch, True Bypass
• Tube: 12AU7
• Power: 4 x AA batteries (allows 20 hours of operation)
• Dimensions: 1 6.84 cm (6.63”) (W) x 15.55cm (6.12”) (H) x 6.4cm (2.52”) (D)
• Weight (without batteries): Bulldog Distortion 1.07kgs (2.36 lbs.), Big Ben Overdrive 1.02kgs (2.25 lbs.), Brit Booster 1.05kgs (2.31 lbs.)