I haven't done direct A/B comparisons of different resistors in the same circuit, but I have noticed that circuits built with different resistor types tend to sound different. Specifically, the Z-foil resistors add a lot of clarity and detail (removing a veil as some describe it), but they don't sound as warm and rich as some other resistors.
Cheap carbon resistors tend to sound a bit dull with less detail. Better carbon film resistors add some warmth and richness.
These differences are fairly subtle and I doubt very much I'd be able to tell the difference replacing a single resistor (although others have claimed otherwise), but building an entire preamp using higher quality resistors definitely improves the sound.
As an example, check out the reviews of the Wyred 4 Sound STP-SE base model and with upgrades. The with Stage 2 upgrades. One of the key differences with the upgrades is replacing most of the signal path resistors with Z-foils.
Several months ago, I completed a DIY preamp where I used Vishay Z-foil resistors (Takman REX shunt resistors in the attenuator) for all signal path resistors. This preamp turned out to have significantly improved detail over the Parasound JC-2 preamp I had been using. It's not often that I have replaced a single component and heard such stark differences. Obviously there were other differences in the circuits, connectors, wiring, etc., but I believe the higher quality resistors had a lot to do with the sound quality improvements.
Cheap carbon resistors tend to sound a bit dull with less detail. Better carbon film resistors add some warmth and richness.
These differences are fairly subtle and I doubt very much I'd be able to tell the difference replacing a single resistor (although others have claimed otherwise), but building an entire preamp using higher quality resistors definitely improves the sound.
As an example, check out the reviews of the Wyred 4 Sound STP-SE base model and with upgrades. The with Stage 2 upgrades. One of the key differences with the upgrades is replacing most of the signal path resistors with Z-foils.
Several months ago, I completed a DIY preamp where I used Vishay Z-foil resistors (Takman REX shunt resistors in the attenuator) for all signal path resistors. This preamp turned out to have significantly improved detail over the Parasound JC-2 preamp I had been using. It's not often that I have replaced a single component and heard such stark differences. Obviously there were other differences in the circuits, connectors, wiring, etc., but I believe the higher quality resistors had a lot to do with the sound quality improvements.