Over the years I have gotten into some debates with people on the very topic of resistor type in audio with pretty much everyone saying that it makes no difference. It seems there is a lot of misinformation out there considering you have some manufactures such as “susumu” manufacturing specific resistor series for “audio use”, meanwhile other people saying this is all a myth and a gimmick(audiofoolerly). While any component labeled for specific uses means nothing in and of itself, the actual specifications of such components do. While the amount of “noise” produced by a resistor on a power rail or a signal line may be negligible in either case, that is not what I am getting at here. The main proven benefits to thin film come down to their manufacturing process leading to an availability in a stricter tolerance. Taking things one step further, surface mount technology resistors are also available in tighter tolerance than through hole. Any such search on a distributors site such as digikey can tell us this much (which will be one of my many arguments for why surface mount technology is superior in another article).
So why should you even care about the tolerance of a resistor? After all, isn’t that just knit picking?
While a lot of engineers may just pull out their drawer and slap on whatever standard 10kohm resistor falls out of there first, or use whichever package or tolerance is cheapest, they may unknowingly be causing significant harm to the audio quality. Why is that? Well anytime we are taking into account devices such as opamps with fully differential input stages we must understand that their common mode rejection ratio performance is inherently
affected by the matching between their input stage channels.
(To learn more about CMMR check out- https://givemebass.com/cmmr-in-audio/ )