As I've tried to point out before, audiophoolery and gutarphooloery are different things. A hi-fi system is designed to reproduce an existing signal as faithfully as possible and thus is (or should be) always operating within its linear region. A guitar/amplifier system is creating a sound for performance purposes, musical or otherwise, interacting with a human operator. It is frequently operated beyond linearity (all those references to "creamy valve distortion"!) and that alone implies that different valves (samples, never mind brands) will give different results. Add to that the influence of cables of indeterminate length, designed for robustness over other properties, connected to high impedance outputs, and you have a veritable soup of possibilities. It is the general failure to grasp this essential difference which gives the whole cable B
thing traction in hi-fi circles.