For those who truly believe that carbon comp resistors improve the sound of your tube amp, here's your chance:
Electronic Goldmine - Giant Deluxe Box of Resistors
Note: I have bought parts from these people for years. I have no interest in the company other than as a valid parts supplier. I will be placing another order for their rotary encoders, but not for these resistors. I only use carbon comps for grid stoppers and I already have a few thousand!
Some, but not all, carbon comp resistors exhibit a slightly nonlinear resistance / voltage characteristic, and therefore can impart a unique distortion signature.....hence the belief that they are magical.
They are also non inductive and therefore good stoppers on G1 in a tube, and the gate in a mosfet. The use as a stopper does not impart any voltage drop across the resistor, therefore does not create measurable distortion.
Most film resistors use a spiral cut in the film to trim the resistance value, and therefore are slightly inductive. This is usually not an issue except with low value resistors on mosfets, and high Gm tubes with good RF characteristics.....In these cases a stopper can actually MAKE a part oscillate.