The following is a list of prices for some capacitors sold by Mundorf, a massively audiophile-approved component company. Each capacitor is within the same product range ("EVO"), and apart from some differences in max voltage and tolerance (450VDC ~ 1000VDC, 3% ~ 2% tolerance) are all 1µF polypropylene film types designed for use in power decoupling/filtering stages in audio circuits.
1µF Mundorf Polypropylene Film Caps:
╔════════════════════════════════╦═════════════╗ ║ Series ║ Price ║ ╠════════════════════════════════╬═════════════╣ ║ EVO ║ €3.50 ║ ║ EVO OIL ║ €7.99 ║ ║ EVO Silver.Gold OIL ║ €25.90 ║ ║ EVO Supreme Silver.Gold OIL ║ €69.90 ║ ╚════════════════════════════════╩═════════════╝
I have little doubt that in a blind ABX listening test there probably isn't a single person on the planet who could consistently differentiate the pricier caps with greater than 50:50 accuracy, and that realistically what is being paid for is some combination of bragging rights and capacitor packaging sexiness (phwoar, look at that black and red one).
I know questions have been asked about whether different types of audiophile caps are anything but snake oil, but specifically my questions are:
Given a single capacitance rating, would it even be physically possible for the human ear to hear the difference between the capacitors within a single "audiophile" capacitor range, as the Mundorf EVO range above? (e.g. swapping the standard "EVO" out for an "EVO Silver.Gold OIL")
Would the difference in audio output even be instrument-measurable, and if so, what metric would constitute an "improvement" in quality? Lower THD? Lower ripple? Increase in pixie dust?