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Topic: BOM ist jetzt in unserem WIKI (Read 4822 times)
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peter_77
Urgestein
 Offline
Posts: 735
THE mcHF and UHSDR forum !
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Re:BOM ist jetzt in unserem WIKI
« Reply #16 on: 08. October 2017, 14:04:05 »
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But the general question remains if we could replace all the alu elkos with tantalum ones ? Or do alu elkos have a technical advantage over tantalums ? I wonder why they are used mixed with the alu ones if we can have just a pure tantalum bom here.
They have a better mechanical stability, less height as i said and their overall handling is more robust.
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KevinA
Neuling
Offline
Posts: 16
It's English
 
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Re:BOM ist jetzt in unserem WIKI
« Reply #18 on: 08. October 2017, 15:38:23 »
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Of course you can replace them! But
- they are cheaper than tantalum
- the existing layout uses Elkos (and we will not change it for such reasons)
vy 73
Andreas
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From a Codec Manufacture:
" In general, there are 3 types of capacitors that will be available in the values that are appropriate as AC coupling in most signal paths: electrolytic, tantalum and ceramic. Each has strengths and weaknesses.
Electrolytic capacitors are generally the best performing for this purpose. They are very linear when biased by the Common Mode voltages present in most SigmaDSP audio paths and their low ESR (Equivalent Series Resistance) makes them attractive as an 'invisible' component when designing a circuit. They are fairly low cost as well. However, electrolytic capacitors have quite a large footprint and they will suffer from degradation of value and performance over time - especially in a high temperature environment. They literally 'dry out' and become a high pass filter in the signal path. High temperature versions are available and will hold up well over a long period of time.
Tantalum capacitors are a reasonable alternative, however they are more expensive than electrolytics and are not available in as many values. As polarized capacitors, they must also be biased, however I have not found them to be as linear in an audio path as electrolytic capacitors. Some people say they "don't sound as good," however static single-tone distortion tests might not reveal any differences. On the positive side, tantalums do not dry out and so are appropriate for a long term high temperature environment. They are generally smaller than electrolytics for the same value.
Both of the non-ceramic types will hold their capacitive value under use condition, unlike ceramics....
Ceramic capacitors are generally not recommended for use as AC coupling in audio. They are attractive because of the size, cost and low ESR. However, when most ceramic capacitors are biased, the capacitive rating can decrease by as much as 50%! The higher grade (X7R) types suffer less from this, but you should be aware that a 1 uF might be acting like a 0.68uF in the circuit. We have also found that ceramic capacitors suffer from microphonic effects: the audio passing through the part will actually physically resonate and cause distortion! I would only use ceramic capacitors in the audio path where performance is not an issue, but size and cost are your higher priority. NP0 and C0G are the best of the ceramics, however I don't think you will find these types available in appropriate values."
https://ez.analog.com/thread/3465
High Temp Electrolytic Capacitors for low ESR and linearity.
Kevin K2AAE
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Kevin K2AAE
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DL8EBD
positron
Urgestein
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Posts: 1908
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Re:BOM ist jetzt in unserem WIKI
« Reply #19 on: 08. October 2017, 15:52:22 »
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Kevin, thx for the very good explanations 
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