The Tube Box lends to a solid state amplifier that characteristic valve sound required by any self-respecting guitarist.Guitar valve (or ‘tube’) amplifiers, as used on stage or in the studio, derive their characteristic sound from the clipping behaviour of the valves when overdriven. Whereas the effect of clipping in a solid state amplifier is very unpleasant (and for many this alone is reason enough not to touch them), it is common to drive valve amplifiers into clipping. But with a disadvantage: if a valve amplifier is to be overdriven, the volume control must be turned all the way up. This does not always go down well with the other band members (or with the neighbours!). With the Tube Box circuit described here, which sits between the guitar and the valve amplifier, this is not necessary. The tiny unit applies the desired distortion to the input signal of the amplifier. The controls on the Tube Box are two potentiometers and two switches, which allow the user to choose from a wide range of possible settings, making the unit suitable for the whole spectrum of guitar music from smooth, warm blues to screaming heavy metal.