Resistor non-linearity - there's more to Ohm than meets the eye

Discussions on (audible) differences between types of passive components like resistors range far in audio engineering. Ed Simon put his money where his mouth is and developed a bridge-type measurement setup that enabled him to measure resistor non-linearity down to -170dB. The article shows that there are indeed quite substantial non-linearity differences between resistor types. But it also shows that the best ones are not necessarily the most expensive ones and that there may well be something to the excellent reputation of old, obsolete types touted by some designers.