On the bass model, dial in the amount of amplifier overdrive and additional distortion using the drive knob. On the x-ray, play with the shape knob to get the desired distortion tone. On the x-ray bass model, dial in the amount of additional overdrive using the drive knob. On the x- ray bass, the drive knob also has a significant impact on the amount of amplifier overdrive. Here's a somewhat representative sample of what the x-ray sounds like.
All samples have a short uneffected phrase before the x-ray is engaged.