Too late.... if I wanted to get a reputation as nasty.
I need a way to both disagree and dislike a post. What a load...
ak
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Too late.... if I wanted to get a reputation as nasty.
or even a perfectly insulating atmosphere, unless your circuit is kept in a vacuum that is.
like inside of a vacuum tube? no way current can flow in those
At microwave frequencies, early formulations of Teflon became a lossy conductor. Surprise!
ak
I did MIL designs too, but if we did use solid tantalum caps, we had to get permission because of the fact they would blow up if the inrush current was not limited or controlled. In one design, we had to pay Sprague to surge test all the solid tant caps to weed out the ones that were going to die and pay for all the ones that did. VERY EXPENSIVE but my idiot boss's design used solid tantalums so we had no choice.While tants are obviously not good for audio work, I wouldn't damn them quite so generally. I pretty much worked in the military field for 40 years and the small signal polarized capacitors were almost all tantalums
I did MIL designs too, but if we did use solid tantalum caps, we had to get permission because of the fact they would blow up if the inrush current was not limited or controlled. In one design, we had to pay Sprague to surge test all the solid tant caps to weed out the ones that were going to die and pay for all the ones that did. VERY EXPENSIVE but my idiot boss's design used solid tantalums so we had no choice.
There was an option called "wet slug tantalum" that did not blow up because they had higher internal resistance but they wouldn't work in our design because..... they had higher internal resistance. They didn't work at the cold temp range of the unit.
Anyway, tanatlums were a giant PITA and very pricey but we had to use them sometimes.
In my opinion, anybody broadly supporting the use of tantalum capacitors for whether for audio or not has lost their credibility with me. I've been reading about and doing electronics pretty much my whole life, and some of the long-winded discussions about tantalum capacitors sounds to me more like somebody who learned the jargon but doesn't really understand the whole concepts. Why would anybody so strongly support tantalum caps unless they are selling them?
I don't think they are good for even general use, much less in audio coupling. So many IC spec sheets call for tantalum bypass caps. I've always ignored them and never had an issue by not using them. For audio, if you can't go with a poly film cap for reasons of cost or space, I would go with electrolytic - but only bipolar types. With or without a DC bias the bipolar types show less distortion than polar types. If at all possible, a bank of poly caps (PPS or maybe PET) would be better.
I cringe when I have to use a electrolytic for audio, but if I were to use a tantalum, I would be nuts.
The point was that any solid Tant has no "safe rating" for uncontrolled surge current. Their impedance is low enough that they can easily blow themselves up. We were specifically restricted from using solid tants in MIL designs unless there was circuitry to prevent surge current damage. The design in question used a wet slug tant but it didn't work at the -55C lowest operating temp where the ESR went up. So we had to use solid Tants but some of them blew up. Sprague screened enough caps to get us "surge proof" caps and certified they would not blow and the procurement officer signed it off.Oh yes, you do have to use tants within their ratings but that applies to any component.
Doesn't that apply to any capacitor by definition.The point was that any solid Tant has no "safe rating" for uncontrolled surge current.
That is another advantage of solid tants that I forgot to mentionTheir impedance is low
The Mil-std-Hdbk 217 was clear about Tantalum reliability with the ESR of the attached circuit and surge currents where the failure rate factor rises rapidly with lower driving impedance to old Tantalum caps. reference 70's and 80's
Since the 90's as I referenced in #55, the chemistry has improved in Tantalum's which now serve as more reliable than Alum dielectric. e-caps.
Many Japanese sourced caps fulfill this now ( and even American companies with Japanese partners)
In the case of Vishay-Sprague who are now 50yrs old, they have acquired brands and recently Sprague Polytech which had it's roots in Tantalum caps from Hitachi, in 1958
From my extensive work with 6 major Japanese and many other international companies, nobody takes reliability more seriously than Hitachi for components and systems in the world.
It is all about attention to quality details in design, materials and process controls.
Capacitor material source quality is measured in ppm and ppb for contaminants.
When US companies were making disk drives with 50k hr MTBF, Hitachi had field experience of >1 million hr MTBF back in the 80's in Japan. Never perfect, just better and I knew everything about quality inside Seagate, Maxtor, and all the others...back then. ( & was even offered the Quality Mgr position at Seagate becuase I knew their quality weaknesses and their competitors better than others. ) but I digress, this is old experience, but still relevant.
e,g, Below is just one of many Japanese products in an international corporation with high-rel Tantalum
https://www.digikey.com/en/product-highlight/v/vishay-sprague/tm8-series-tantalum-capacitors
Well, I did it anyway, just for fun:
I used a HP8903B audio analyzer and connected a single pole passive RC highpass filter on the output of the audio generator running at 5Vrms @ 160Hz. R was 600Ω, C was 1µF and the distortion analyzer was connected across the resistor. The results are below:
Direct connection with 600Ω load resistor only (No capacitor) = 0.002%
Distortion with no DC bias on the capacitor under test:
Metal film = 0.002%
Electrolytic = 0.016%
Dip Tantalum = 0.425%
Ancient axial Tantalum = 0.028%
SMD Ceramic = 0.420%
Distortion with 9V DC bias on the capacitor under test:
Metal film = 0.0035%
Electrolytic = 0.029%
Tantalum Dip = 0.190%
Ancient axial Tantalum = 0.022%
SMD Ceramic = 0.609%
The only result that puzzled me was the Ancient axial Tantalum until I googled it and saw that it was still listed on the NASA site.