Distorting bass has always been a very challenging engineering endeavor: in order to achieve a punchy, and aggressive distortion that is also full and fat-sounding you need to reconcile two contradicting conditions:
The tightness comes from attenuating bass frequencies before saturation, which will also result in a very thin signal. But boosting the lows will result in additional, unwanted fuzz.
The Microtubes X is our solution to that problem in a very compact form: The signal is split by two variable low-pass and high-pass filters at the very very beginning. The high-pass signal (mostly mids and treble) is distorted using CMOS circuitry, just like our older Microtubes pedals.
The low pass-signal (all bass) is left untouched. Letting the high side be all crunch, attack, and rich harmonics while mixing back the lows to add gargantuan size to the overall mix.
The result is virtually unlimited fullness, size, aggression, and definition, regardless of how old the strings, and boomy or thin instruments. The Microtubes X offers all of this in a compact form, with very few controls to tweak, making it almost impossible to dial wrong.