With the many manufactures of capacitors these days you are bound to run across some part series designated for “Audio use” with little other info available to explain for what audio purpose specifically they are intended for and what makes them so great. For instance, we have nichicon with their “MUSE” series that they claim are for “first class audio equipment where qualitative and quantitative comfortableness is required.” Then we have ELNA with their “SILMIC” series with unsubstantiated claims such as “Improves the midrange responsiveness and low range richness there in” due to some “silk fibers” added to the material. What’s common typically is that they don’t even specify for what area in circuit these capacitors are for and that leaves it up to the designer to make assumptions.
Let me be perfectly clear: not all engineers think rationally!
For example, some engineers may read the above claims and just “assume” them to be true because the manufacture can’t possibly be trying to mislead anyone and they do a lot of testing right? But it’s undoubtedly true that such dogma is intended to confuse the designer even more in an effort to gain more sales on what is, to be completely honest, cheap capacitors. This can be realized by the complete lack of mention to “coupling” or “decoupling” applications by the manufacture and the specs indicating poor function in either. For example, the majority of engineers understand that electrolytic capacitors are not great for coupling purposes(input filtering) in audio due to their high distortion, high tolerances, and ability to change over time(or at least so they thought, until they came across these magical capacitors.)
So they may assume for what other purpose could these possibly be for besides decoupling? So you may have an engineer wondering if they should be placed on a high power supply rail instead? Heck it says “for audio”, let’s just use them everywhere we can!
What really matters are the specs.
Placing one of these capacitors in any area other than the trash bin would be a painful atrocity to bear witness to. The fact that these manufactures don’t give real engineers much pertinent technical info really says a lot itself. Also the little info they do happen to provide such as typically “1,000 hours rated life at 85C” are just as horrible figures as the 20% tolerance if used for any type of coupling or filter application. Don’t bother, and for choosing the correct type of capacitor for your audio design check out- https://givemebass.com/what-capacitor-type-you-should-use-in-your-design/
For help in choosing the correct value for input filtering check out https://givemebass.com/what-value-input-filtering-capacitor-to-use-in-your-amp/