Electronic – Normal capacitor vs. audio capacitor

audiocapacitorcondenser-microphonemicrophonepower supply

I'm building a power supply for old Schoeps CMT30F microphones. Standard condenser mic are 48V-powered nowadays, but these are 60s/70s Schoeps mic from RadioFrance/ORTF, customized at that time to be -9V or -10V powered.

I need to add capacitors to avoid the 9V to go in the preamp / audio interface.

I was told to buy "audio capacitors polarized 100 µF, 50V, preferably Vishay" (formerly Philips?). These are more than 3€ per unit, and these Vishay are 11.89€ per unit!

Question: what kind of difference is there between such a capacitor, for audio applications, and a bog-standard 100 µF / 50V, that costs 0.20€, i.e. 15 times less/60 times less?

Will the difference be hearable in the audio frequency spectrum?

By the way, here is the … hum … sche … schematics of the power supply I'm about to build. The capacitors are the 2 things in pink near the audio interface (bottom of the drawing). Do you think it's more or less correct?

Best Answer

Let's forget about audio for now and try to find where the price difference lies in the specific products you mentioned, first.

  • Main reason: the ebay seller of the Vishay cap seems to mistake his customers for cash cows. The exact same cap on Digikey is less than 1€ (unit price - it doesn't have the same product code: MAL214651101E3, but this is just a packaging difference).
  • The cheap cap is specified for 85° (according to the product range in which you found it - because it has no datasheet). The Vishay cap is specified as 2500h to 6000h at 125°C, which is very good, and therefore expensive.
  • The cheap cap, as I mentioned, has no datasheet. It means it probably comes from a huge stock of whatever no-name manufacturer (the one which is cheaper at the time the seller needs to reorder from the manufacturer). It doesn't necessarily means it's crap (but don't expect exceptional lifetime/tolerance/ESR/...), but it means its specs could be different from order to order.

Now for the audio part:

The datasheet of the Vishay cap nowhere mentions audio in it. Indeed, What seems to be interesting with this specific product range is the lifetime and ripple current capability. Which makes it ideal for high-power supplies used in industrial environments.

Nothing to do with audio DC blocking.

Conclusion: Both parts you linked will probably have the same performance for audio applications. The Vishay will likely last much longer, but audio isn't very demanding anyway.

Now, when looking for excellent performance in audio applications, people tend to prefer film capacitors (e.g. polypropylene) rather than electrolytics because they don't degrade over time. But for 100µF, it will cost an arm and a leg (why 100µF, by the way?? It seems pretty high - 50V seems way above what is really necessary, as well).

Anyway, don't fool yourself too much with "audiophile" stuff. Be pragmatic.

Added later

Following your edit where you mention another Vishay cap at 11.89€: again, looking at the specs, these are not designed specifically for audio (actually, the designers certainly did not have audio in mind at all, here, and they would probably laugh their heads off, if they saw it used as such). They are designed, as the datasheet says explicitly, with "high reliability" in mind. I don't really know what that actually translates to, and whether it really justifies a x50 price tag, but then again, this certainly won't lead to better audio performances.

You're actually not looking at typical "audiophile" stuff here. And I'm surprised your friend suggested those kind of caps. These are just expensive, industrial-grade capacitors, not targeted for audio applications at all.

So... There we go, I'll bite, and I'll tell you what is the typical "über-audiophile" cap that amateurs recommend on forums, and that often lead to opinion wars: the Rubycon Black Gate! Tadaam... Well, they went out of prod about 10 years ago, but if you search on the internet, you can find some 100µ 50V for about 50$.

Be careful, some of them are fake.

More seriously, there are reputed manufacturers who currently produce electrolytic caps specifically designed for audio. For example, the SIMLIC series from ELNA. Those sell at a much more reasonable price (typically around 1€ for a 100µ 50V), and if your question was whether those kind of capacitors really specifically designed for audio (unlike all the examples you suggested) were worth it or not, it would actually be more difficult to give a definitive answer...

My guess is: If you did a real blind test, you most likely wouldn't be able to tell the difference. But sometimes, at a hobby level, there are some psychological factors to account for when designing stuff, and, if you can go to sleep at night with a sweet smile on your face just because you know your signal goes through an "audio-grade" capacitor, it may be totally worth the 0.80€ difference, even if it provides objectively no improvements in sound... Up to you, I won't judge.

For professional audio equipment manufacturers, it is different. I wouldn't trust a designer who would not make the actual measurements and compare the real capacitors performances in situ.