Originally Posted by soekris
Thick film resistors are a big NO in audio circuits, by themselves they are both noisy and unlinear....
Use Thin film, like Susumu RR series, Digikey and Mouser have very good stock on those.
I'll agree, and add that the Susumu RG series is only a little more expensive than the RR series, far more stable, and readily available at Digikey and Mouser. The NiCr resistance element is sealed with a glass-like coating and laser trimmed through the glass, so their drift is extremely low. The RR series is sealed in resin, and it's less stable over time.
You can get lower temperature coefficients in the RG series too, something I feel is important to counteract their physically small size and the resulting potential for distortion from signal induced heating of the element. Their 10ppm/degree parts are extremely stable and sound/measure very well, and the standard 0.1% 25ppm RG parts are no slouch either. The Panasonic ERA series are almost as good, but the Susumu RG are a little better IMHO. The 2012 size is about as small as I'd use - they make smaller 1608 parts that seem to be more common, but I don't trust those to have low enough distortion. 3216 would be a better size than 2012, but they're not generally available off the shelf in oddball values.
I have used some larger thick film resistors for some power supply uses, but only because at low values like 100Ω, they really aren't completely awful, and in this case they are loaded into a giant 470µF cap and then a regulator, so their noise and distortion will be lowpassed and regulated away. Other than a few exceptions like this, where I needed the huge size and power rating of a thick film, never use thick film for any audio use.
Last edited by Monte McGuire; 20th June 2018 at 02:02 AM.
Reason: comment on resistor sizes