Tantalums

[mattc]

I've been reading the excellent Where to Buy What article on the Aion Electronics website (https://aionelectronics.com/resources/where-to-buy-what/), and had a question on tantalums.

I remember reading when I first started building pedals to avoid using tantalums, so I was surprised to see their recommendation in the Aion article.  Can you guys share your opinions on the use of tantalums?  Specifically, why you would use them in place of an electrolytic, and vice versa.

Thanks!

[kgull]

Specifically, why you would use them in place of an electrolytic, and vice versa.

A good rule of thumb is if you can't answer that question, stay away from tantalums! This has nothing to do with quality and everything to do with safety.

When tantalums fail, they fail spectacularly:

If you really want to know more about using them, this stack answer is far better than anything I could come up with.

[Ralfg]

My understanding of the tantalum problem is the mineral they are made out of is a conflict mineral, so you should avoid them. However from what I read Kemet tantalum are supposed to be conflict free.

[midwayfair]

Tantalum electrolytics can be made extremely small; and it has a very, very low ESR; they don't leak much; and they last a very long time compared to aluminum.

There are aluminum electrolytics now that can compete with the low ESR, but this is a relatively recent development, so you'll see them in some older circuits where the ESR was more critical than other factors. They appear on old tube mic cathodes, for instance.

There are also mini aluminum electrolytics that can sort of compete in size with normal sized tantalum capacitors. However, tantalum will probably always win the size war. They certainly beat the snot out of poly caps in the size race, so if you need low leakage with high capacitance they may be the right call.

The main problem with their failure -- and I've made them explode before -- is that they fail AS A SHORT. You'll get an open circuit when an aluminum cap fails. However, you can also, hypothetically, use this to your advantage by picking the right type of cap in the right places to ensure safety or continued function in the event of a failure.

People who claim that they sound awful usually are using their imaginations, not their test equipment, but there may be situations where measurements would show a difference for reasons that have nothing to do with capacitance differences.

Any time someone tells you to just avoid a certain type of part, take it with a grain of salt. If something was a universally better dielectric, that's all that would be made and you wouldn't even be asking about the choice, right?

[reddesert]

IMO, there are components that exist for some good reason, but there isn't a good reason to use them in DIY audio circuits, especially guitar pedals (which are low-fi compared to say a mixer or synthesizer).  Sometimes people use these components and advertise them for, I don't know, precision bragging rights. Examples, and this is very much IMO, include very precise resistors, tantalum caps, and hi-fi precision op-amps.

[m-Kresol]

they last a very long time compared to aluminum.

this is one of the major aspects for many applications I think. For our purposes, it's not necessary in terms of the other advantages (except maybe size). I have yet to find an application in our field where a tantalum would be crucial to the circuit.

capacitor technologies should really be seen as complementary technologies. Polymer film, electrolytic and ceramic (mlcc) all have certain aspects, which can make them favourable for one or the other application. And obviously, there's the price point, which often is a determining factor for the end user.

[galaxiex]

I wouldn't use tantalum caps willy-nilly to replace electros or any other kind wherever.

But if a circuit specifically called for them, the rules are....

Be very certain not to exceed the cap rated voltage, and

Never ever ever ever hook them up backwards. Be very certain of the polarity.

[mattc]

Thanks all, that helps clear it up a bit!