Low-ESR 1uF electrolytic (hard to find)

Discussion in 'Datasheets, Schematics, Manuals and Parts' started by TTL, Aug 11, 2017.

  1. TTL

    TTL

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    Does anyone know of any (quality branded) 1uF (16V or higher) electrolytic capacitor?
    I've been trying to find it within the Panasonic FR/FM/FC (low-ESR) series, but they don't go that low.

    I'm trying to find something which will replace tantalum capacitors in audio paths (I've been warned that tantalums can explode and/or fail by short-circuiting unlike electrolytics which just dry out/stop working), and low-ESR is the way to go, or so I've been told.
     
    TTL, Aug 11, 2017
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  2. TTL

    kellys_eye

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    Why not just use the right part - the tantalum? If they aren't broke, don't fix them.

    Tantalums are not inclined to 'explode' in audio signal paths - they tend to do so on power supply lines though.... even then, not 'always'.
     
    kellys_eye, Aug 11, 2017
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  3. TTL

    TTL

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    I was under the impression that these were outdated components by today's standards and better be avoided. Not so?

    So your conclusion is to (maybe) recap tantalums where used in power situations (typically connected between +V and GND I assume?) in order to avoid damage if they short-circuit, but keep the tantalums in signal paths?
    How about the possibility of explosions? That in itself appears destructive, which I'd rather avoid (even if there's only a slight chance it might happen).

    The only 1uF electrolytics I could find in the Panasonic range are within the NHG and M-series. An overview of all Panasonic's radial electrolytics puts them in the "long life/high ripple" category. The datasheets however don't specify their ESR and/or impedance (is that the same thing?) values, unlike the "low-ESR" categorized Panasonic caps. So likely Panasonic isn't too proud of those ESR ratings :eek:

    I've done a lot of datasheet reading for the Panasonic caps (as they have the broadest range my supplier sells) but don't know much about the other quality brands -are there any low-ESR/long life/105C caps available from anyone in 1uF?
     
    TTL, Aug 11, 2017
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  4. TTL

    dorke

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    It is strange,you see,
    tantalum capacitors aren't usually used in audio circuits.
    Maybe you are confusing them with polyester caps. or such.
    A photo may help.
     
    dorke, Aug 11, 2017
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  5. TTL

    kellys_eye

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    Are the capacitors you are concerned for actually connected in 'high ripple' circumstances?

    Values for ESR are smaller as the value of the capacitor drops so sub 10uF become less of an issue unless you're talking HF ripple in SMPS outputs and decoupling locally (say at IC's) which is then normally by MLCC type capacitors anyway.

    As stated, if these are in audio circuits then where is the high ripple current coming from?
     
    kellys_eye, Aug 11, 2017
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  6. TTL

    TTL

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    I'm no expert, but I don't think their use is in high ripple situations.
    I'm building an analog vocoder (an early 80's design) and I'm enclosing screenshots of the sections where tantalum capacitors are being used.
    tantalum_input amps.png

    tantalum_internal excitation.png

    tantalum_LED ppm.png

    tantalum_lowpass filter.png

    tantalum_output amp.png
     
    TTL, Aug 11, 2017
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  7. TTL

    Bluejets

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    Did you add the red markings referring to "tantalum"?
    Otherwise I would have read the drawing as standard electrolytics.
     
    Bluejets, Aug 11, 2017
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  8. TTL

    kellys_eye

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    Either type will work.

    Tantalums are good for timing circuits or low ESR requirements neither of which are specific to the schematic you show (ETI magazine perhaps??)

    Solid capacitors (MKT, plastic film etc) would also work - although on the power lines I'd still use electrolytics.
     
    kellys_eye, Aug 11, 2017
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  9. TTL

    hevans1944 Hop - AC8NS

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    One microfarad, sixteen volt, dipped tantalum capacitors are quite common and relatively inexpensive. The make excellent coupling capacitors in low-frequency applications because they are tiny compared to other capacitance dielectrics, therefore occupying less precious board space.

    ESR is generally not a consideration unless you are using a capacitor in a high ripple-current power supply filtering application. They make excellent bypass capacitors and are typically sprinkled liberally around the circuit board, mounted close to the power pins on the devices they are protecting from power line transients. They also prevent high-speed logic devices from creating power supply transients affecting other devices on the circuit board. Any serious experimenter should own a bag of a thousand or so, IMHO.

    Tantalum capacitors, like any other electrolytic capacitor, DO need to be biased properly so bear that in mind when using them. Don't just willy-nilly plug a tantalum in without making sure there will be DC voltage across it in the correct polarity. If not, use a non-polarized capacitor.

    This is NOT obsolete technology. However, they can and will explode if subjected to more than their rated voltage. Other capacitors will also fail when excessive voltage is applied, but not usually as spectacularly as tantalum capacitors. I think you are worrying needlessly about the "safety" of tantalum capacitors. Re-chargable lithium-ion batteries would be more worthy of concern.
     
    hevans1944, Aug 11, 2017
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  10. TTL

    dorke

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    The application is a Vocoder.
    i.e. audio is degraded anyways.
    That is why they allow themselves the use of tantalum caps in the audio path.

    It isn't recommended in HiFi audio, because of the poor behavior of tantalum's behind very low frequency audio (bass+) ,polyester caps are to be used instead.

    Other tantalum are used for filtering of power supplies,that is fine.

    In your case,there is no need to change any caps because of "safety issues" .
     
    dorke, Aug 11, 2017
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  11. TTL

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    1uF mlcc caps are easy to get these days. They have a very low ESR, but have capacitance that tends to vary with voltage, and can be microphonic. Their failure mode isn't so pyrotechnic :). Surface mount mlcc's can fracture if mechanically stressed.
     
    (*steve*), Aug 11, 2017
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  12. TTL

    TTL

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    Yes, I added the red markings and "tantalum" references myself.
    The parts lists for each board (such as the one enclosed here for the input amp boards) specifically states "tantalum". As you can see, there are also electrolytic capacitors in the list, so I haven't misunderstood the parts lists, or they must have had a specific reason for using tantalums along with electrolytics (perhaps as a space-saving measure or the techology was different back then so electrolytics couldn't do what tantalums could?).

    The project is as Kellys_eye rightfully pointed out, from the ETI magazine, specifically the September and October 1980 issues.

    I see there are lots of other replies here, so I'll read through that, but wanted to clear up the above first.

    parts list_input amp.png
     
    Last edited: Aug 11, 2017
    TTL, Aug 11, 2017
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  13. TTL

    TTL

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    I see there are different views on the subject, which is OK, and also tells me that electrolytics can indeed be used to replace tantalums.

    Havans1944: if I understand correctly you're saying that for those schematics I just posted (various parts of a vocoder) there is no need for low ESR capacitors, though they are needed in power supplies and I assume you're referring to the electrolytic capacitors right after the rectifiers? When you talk about "bypass capacitors", are these any of the capacitors that go between +V and GND?
    Here are some schematics with my comments in them to further illustrate what i'm talking about:

    PSU board_ripple.png

    psu_bypass.png

    slew rate_bypass.png

    You said "Tantalum capacitors, like any other electrolytic capacitor, DO need to be biased properly so bear that in mind when using them."

    I'm not sure what you mean by "biasing" -is this just a term meaning "take care when soldering the capacitor in the circuit so that + and - goes the right way"? I've never looked at that as a problem, just the way an electrolytic (unless bipolar) is to be used.
    So to conclude you're saying that if inserted the correct way and used within their voltage limits they shouldn't pose any threat to the rest of the circuit? But you're not saying that electrolytics can't be used in place of tantalums without any ill side-effects?


    dorke: It seems you're confirming the opposite of my fears: you're claiming that tantalums are the ones which might affect audio negatively, not electrolytics? So if I wish, I can exchange (i'm actually rebuilding the vocoder on new PCBs, reusing some of the parts) the tantalums for electrolytics and get the same (or better) audio quality?


    kellys_eye: from what I understand you're also confirming that I can use electrolytics in place of those tantalums without any bad side effects, but I don't need to look for low ESR types, just "normal" electrolytics?
    But if I did replace all those tantalum capacitors with low ESR electrolytics, would that cause any issues, or for the sake of the circuit (and resulting audio) work just as if I was to use "normal" electrolytics but just be a waste of money?
    You also mentioned using solid capacitors -those aren't polarized, are they?

    *steve*: I've never heard of "micc" capacitors. What are they?
    They do seem to have some issues though. If electrolytics work just as well I think I'll go for those.
     
    TTL, Aug 11, 2017
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  14. TTL

    kellys_eye

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    'Normal' electrolytics are generally 'low' ESR when their values are small anyway.

    Low ESR is particularly useful in switched mode power supply circuits and the 105degC rating is preferred too but for linear power supplies this is less important than getting the correct value to keep the ripple low in the first place AND you can get away with the 85degC versions too.

    That circuit (the audio paths anyway) would work with either type but there's no specific reason you shouldn't use what's specified as the horror stories you might read about tantalums is usually without base and certainly baseless in audio applications.

    No, 'solid' capacitors are not polarised and a solid 1μF would work just as well (some would say 'better') than tantalums however if space is an issue you may be constrained by that rather than the need to use tants as specified.
     
    Last edited: Aug 11, 2017
    kellys_eye, Aug 11, 2017
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  15. TTL

    davenn Moderator

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    wrong impression, it is not so ..... tant's are very reliable and still a standard component in today's high tech electronics
    I work on high tech GPS receiver equipment boards that often cost $1000's and they are full of tant's
    Do you really think they would be used if they were unreliable ?
     
    davenn, Aug 11, 2017
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  16. TTL

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Mlcc is multi layer ceramic capacitor.

    When that project was designed ceramic capacitors with high capacitance would have been physically much larger.

    These days some very small and relatively high capacitance ceramic capacitors are available.

    Because their construction has many short layers (as opposed to a long single layer that's wound up, they tend to have quite low ESR and ESL.

    However, along with some very nice characteristics they have a few more that are less nice. The main advance is that the "not nice" feature of "low capacitance" has been knocked on the head.
     
    (*steve*), Aug 11, 2017
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  17. TTL

    dorke

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    In general,
    for HiFi Audio,both electrolytics and tantalums are a poor choice for the signal path .
    The better solution is to use polyester/mayler capacitors types.
    In your case the vocoder compresses voice,degrading it's quality any ways,so it is most probably not important.


    Since your equipment uses a simple line(50-60Hz) rectifier bridge in it's power supply,
    the electrolytics don't need to be low ESR (at such low line frequencies).
    The standard electrolytic caps will do the job fine.
    They are the ones to be use for filtering,as is indeed done here.

    Leave the polarized small value tantalum caps as they are, there is no need whatsoever to replace them.
     
    Last edited by a moderator: Aug 12, 2017
    dorke, Aug 12, 2017
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