By virtue of their electrical properties, tubes generate a special waveform when they're saturated, which is why tube engineering has tremendous tonal advantages over solid state or DSP solutions, particularly for crunch and lead sounds. Tubes enter the saturation zone gradually or softly, which lends tube-driven tone its trademark yet totally unique character.
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Get a new guitar. I had a similar problem with my squire. Once i got a new guitar everything was fine. First try changing settings though and make sure the amps not set to destortion aswell as the pedal !