Electrolytic vs Tantalum cap for audio use

Back in my previous life as an engineering tech for medical imaging equipment, for caps >1 uF we almost always used Tantalum caps. Tantalums were used for DC up to low RF frequencies. Aluminum electrolytic caps were very seldom seen.

In consumer audio equipment, the reverse is true. Tantalums are almost never seen.

Can someone explain why?
 
Tantalum caps have a reputation for spontaneously shorting out and exploding. As well, they don't sound very good when used in the audio path.

In my career as an electronics tech working on medical and industrial equipment I never found a defective tantalum capacitor other than a few that were installed backwards. I think that the reason for that may be that these manufacturers generally use higher quality parts, and tantalums are more difficult to manufacture well.

Take care,
Doug
 
Back in my previous life as an engineering tech for medical imaging equipment, for caps >1 uF we almost always used Tantalum caps. Tantalums were used for DC up to low RF frequencies. Aluminum electrolytic caps were very seldom seen.

In consumer audio equipment, the reverse is true. Tantalums are almost never seen.

Can someone explain why?

Tantalum caps last longer, can have a higher CV density, and in the past had worked better at higher frequencies.

They aren't common in audio gear because they are more expensive, had a dangerous failure mode, and possibly worse as coupling caps. They are also made using a conflict mineral if that's a concern to you.

Al solid polymer caps have caught up in a lot of these areas. Tantalum and polymer tantalum are still best in some applications.
 

ticknpop

Member
Paid Member
2005-05-28 9:43 pm
toronto
I don’t like Naim amplifiers, their cult like reputation far exceeded thier actual sonic merits.

Dayton Wright, AGI, and Threshold (Nelson Pass), Symmetry (John Curl) and others used tantulums in the signal path and power supply in the 1970s.
Standard refurbishing to those electronics today would be to replace signal path tantalums with bipolar electrolytics like Muse or polarized Silmics. Replace Power supply caps with Silmics or long life 105C electrolytics
 
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Of the 69000 tantalum capacitors digikey stocks, 2 have a service life greater than 2000 hours. They cost $137.75 each.
I just bought 140 electrolytic caps rated 10000 hours service life from digikey. They cost average under $1. Nichicon, Rubycon, Panasonic, Kemet
Of the 7 tantalum caps in each 1968 Hammond H100 organ, they were all bad.
Of the 2 tantalum caps in my ST120 2 were bad, and the replacements from the local TV parts shop had popcorn noise. Replaced with COG ceramic.
Of the 4 tantalum caps in a 1980 Allen 300 organ switcher supply, 4 were okay. Replaced them anyway.
Of the 300+ electrolytic caps I've put in organs & amps since quitting work 2008, mostly rated 3000 hours service life or higher, none have failed.
 
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Appreciate all the answers, but I read most of it as anecdotal and/or subjective opinions. What is it about a tantalum cap that makes it less suitable for use in the signal path? Higher ESR? Greater series inductance? Non-linearities in regard to applied voltage? Noisier?
Shorts out in under 2 years. Failed ones in the organs were low resistance, less than 4 ohms @ 2 v. There is a measurement for you.
2000 hours service life is **** grade, my main amp gets that in a year. Most of the digikey tantalum stock didn't even have 2000 hr rating, the service life was "-" . Why do people even buy these? Yeah, low self inductance, but 1 year life products are garbage.
BTW rayma, my brother the PE CE, says the I35 bridge that fell down in Minnesota, nobody EVER calculated the stress on the gusset plate that failed. Designer missed it, both sets of engineers that calculated increased load rating missed it, highway department missed it. Stress exceeded tensile strength of steel of that thickness.
 
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I have used tantalum caps for cathode bypass in tube amps with zero failures and some of those amps are now 15 years old, but they were mil spec surplus.....good quality caps.

Tek and especially HP used tantalum all over nearly every board in their 80's and early 90's vintage test equipment. Much of that equipment is now failing for two reasons. Shorted tantalum caps are #1 on the list. Proprietary Silicon On Sapphire chips failing in HP equipment is #2.

A tantalum cap doesn't go open, or slowly degrade. They fail to a short, and if there is ample current available, a flaming short. I have seen caps fail, catch fire, then burn themselves out, and the equipment continues to work fine without the cap.

Other than these drawbacks, they are good caps spec wise.

In the mid 90's all cell phones were full of tantalum. When the cell phone market exploded, tantalum could not be mined fast enough, and we (Motorola) could not get capacitors. The caps made during those times were often made with less than stellar purity materials, much like some of today's vacuum tubes, which made for short life times, again like some new production tubes.

The ceramics of the day were highly piezoelectric, but the vendors stepped up and invented new High K dielectrics that weren't piezoelectric, and there are zero tantalum caps in a modern cell phone.
 

PRR

Member
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2003-06-12 7:04 pm
Maine USA
www.diyaudio.com
There was a time when Al electros leaked, Tant electro didn't. This got misunderstood as "better", and Tants got used a lot of places they did not need to be. Especially when money was flush (medical gear).

"It is said" the magic sauce in some classic studio mixing consoles is Tants. (It is also disputed.)

The few times I have noted Tants other than casual inspection is when one goes BAM and I have to clean up inside. (I have had one Al cap explode, and it was a *mess*, but it was the size of a soup-can.)

The Al electro racket REALLY upped their game, especially in the Tant-crunch Tubelab mentions. Leakage is way-way down, tolerance is better, lifetime is (can be) better. I would not use Tant in new work; in old, only for "looks".
 
There's a list of conditions to successfully use tantalum caps. Derating, limiting rise times via minimum impedances and never using them in a circuit where the current is unlimited in case they short. And some other stuff. Used correctly, the reliability is excellent. I sometimes use them when rebuilding test equipment, but never in audio gear. I've got a particular test I do that shows more distortion with tants than electrolytics, but it's a bit weird and not accepted by sane and educated people.
 

rayma

Member
2011-04-29 8:37 pm
my brother the PE CE, says the I35 bridge that fell down in Minnesota, nobody EVER calculated the stress on the gusset plate that failed. Designer missed it, both sets of engineers that calculated increased load rating missed it, highway department missed it. Stress exceeded tensile strength of steel of that thickness.

I'll bet those guys never had a second bridge fall down, at least if they didn't go to a monastery or something.
 
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jean-paul

Ex-Moderator
2002-09-20 7:20 am
Germany
Quite some outdated info here. Tantalum caps (especially the dipped types) were a plain disaster in the past. I think we can all agree on that. Everybody knows the old tantalum types to go out with a short and then a loud bang. Most also will acknowledge that because of this they were not the best choice on power rails.

However... modern tantalum caps have very good properties but their black past seems to still hunt them. I use them and don't experience failures but I do use higher voltage ratings than strictly necessary also because of their past :) Whereas the old tantalum types did not have the best properties to use them in the signal path the new ones just sound OK. Personally I have nothing against them anymore.

I don't know if the coltan issue still is valid as this was a big showstopper in the past.

It is a bit disappointing to notice many of the audio DIYers seem to hang in the past but technology has really advanced in the years.
 
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Quite some outdated info here. Tantalum caps (especially the dipped types) were a plain disaster in the past. I think we can all agree on that.
However... modern tantalum caps have very good properties but their black past seems to still hunt them. I use them and don't experience failures but I do use higher voltage ratings than strictly necessary also because of their past I don't know if the coltan issue still is valid as this was a big showstopper in the past.
It is a bit disappointing to notice many of the audio DIYers seem to hang in the past but technology has really advanced in the years.
Give me a 10000 hour @ 105 C rating for less than $177.75 and I might be tempted. 2000 hour rating is still rare. No life rating is still majority. The manufacturers know something you don't.
 

jean-paul

Ex-Moderator
2002-09-20 7:20 am
Germany
Give me a 10000 hour @ 105 C rating for less than $177.75 and I might be tempted. 2000 hour rating is still rare. No life rating is still majority. The manufacturers know something you don't.

AVX TPS series is what I use quite often. These are ultra low ESR solid MnO2 tantalum caps and they have a -55 to +125 degrees Celsius rating and they are reliable. Most manufacturers know things the enduser doesn't know so that is nothing new. I am sure aluminium electrolytic cap manufacturers also know things we don't know ;) What I am even more sure about is that audio is a field where old prejudices never seem to die. Many parts have been improved tremendously but people refer to facts from 30+ years ago and some even use parts from 30+ years ago...

This is what AVX has to say about their MnO2 products (I think infinite lifetime is somewhat exaggerated though :))

High-Reliability Solid Tantalum Capacitors | AVX

The relatively new Nbo Oxicap have a MTBF between 200,000 and 500,000 hours.

http://www.avx.com/docs/techinfo/New_Tantalum_Technologies.pdf
 
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