Vox CT-05 Snake Charmer Compressor


Vox Cooltron series

The COOLTRON Snake Charmer Compressor pedal uses 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.

Tame your tone with the Snake Charmer Compressor. The result? Silky smooth, mesmerizing tone that behaves as it should. The Snake Charmer's compression affects the ratio and threshold of the signal, smoothing out peaks and spikes. At the same time, the Snake Charmer also increases the Gain level to complement the corresponding ratio and threshold settings so that the overall gain remains constant.

There's also a Gain Reduction Indicator that gives you visual cues of the results of your settings. And a High/Low Switch lets you choose between two overall levels of ratio. The Snake Charmer effect pedal is equipped with other controls for Attack, which determines how quickly the gain reduction kicks in, and Release, which determines how long the gain is attenuated. Finally, the High-End Emphasis control fine-tunes the amount of compression applied to the top end of the guitar signal.

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 Vox 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 guitar pedals to run for 16 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 the COOLTRON Snake Charmer Compressor pedal.


  • Connection: Input: x1 (guitar input), Output: x1 (line output)
  • Input / Output Impedance: 830 k-ohm / 4 k-ohm
  • Tube: 12AU7 (ECC82)
  • Power Supply: Four AA alkaline batteries or DC9V AC adapter
  • Battery Life: Approx. 18 hours
  • Current Consumption: 95 mA
  • Dimensions: 168.5 (W) x 155.5 (D) x 64.0 (H) mm / 6.63” (W) x 6.12” (D) x 2.52” (H)
  • Weight: 1,007 g (excluding batteries / 1,102 g including batteries)
  • Included Items: Four AA alkaline batteries

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