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Demonstrating the pitfalls of paralleling capacitors
Demonstrating the pitfalls of paralleling capacitors
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Old 8th November 2018, 11:56 PM   #11
gerhard is offline gerhard  Germany
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Nice.

I have made such measurements some time ago:

< http://www.hoffmann-hochfrequenz.de/...capacitors.pdf >

cheers,
Gerhard
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Old 9th November 2018, 05:13 AM   #12
spaceistheplace is offline spaceistheplace
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Demonstrating the pitfalls of paralleling capacitors
Default Demonstrating the pitfalls of paralleling capacitors

Quote:
Originally Posted by DF96 View Post
'Low ESR' could mean 'lower than average ESR' i.e. lower than an average capacitor of a similar type.

'Low ESR' could mean 'sufficiently low that it does not sufficiently damp an unwanted resonance in my application of this capacitor'.
Thanks. I was looking for an example in a familiar (audio) / simplified / standard application in an honest attempt to better understand. That’s kind of like answering “I prefer a car that is slower than the average car in a similar price range and engine size for a given driving style and geographic locale in instances where it might be advantageous.” To “why do you like slow cars and can you provide an example of when its slowness is useful to you?” It walks around the subject but does not illuminate it.

Can you provide an example, such as in a power supply or cathode bypass capacitor or other area that many here attempt to utilize a film cap with a Electrolytic? What about replacing the Electrolytic with same value film capacitor? I imagine avoiding low esr does not imply searching for the highest esr, there must be upper and lower boundaries? He seemed also to insinuate a general distaste, not application specific.

I believe I read some information in Morgan Jones’ book that advocates a low value film cap in the order of 1/100th in parallel with an Electrolytic. This seems to be commonly quoted as logic for this practice. I’ll have to take another look as I’m likely misunderstanding a critical piece of information. Perhaps the RF performance of the bypass capacitor is of utility in tube circuits?
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Last edited by spaceistheplace; 9th November 2018 at 05:24 AM.
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Old 9th November 2018, 07:06 AM   #13
davidsrsb is offline davidsrsb  Malaysia
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When I was decoupling early NE5539 video amplifier opamps, I found it best to use no more than x100 steps in value eg 10uF+100nF+1nF Something like 10uF+10nF and I got a wobble in the swept frequency response These were THT capacitors in those days
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Old 9th November 2018, 10:51 AM   #14
DF96 is offline DF96  England
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In many audio capacitor applications ESR does not matter very much, although that does not seem to stop people worrying about it.

ESR will always be an issue when a cap is 'bypassed', as it is usually ESR which dampens the parallel resonance. ESR may matter in a PSU with high ripple currents, because it adds to heating and may increase ripple. In each case the designer needs to think. To determine whether a particular circuit requires some ESR involves some reverse engineering - it is not really open to 'recipe' level 'engineering'.
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Old Today, 06:17 AM   #15
N101N is offline N101N
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spaceistheplace,
low ESR has come to be regarded as the principal indicator of capacitor quality.

Low ESR means higher instability and distortion. Without relying on numbers, I only use film capacitors and older production electrolytics from venerable manufacturers with a fairly high volume to capacitance ratio. In reality, ESR is never too high, but it does not alone ensure good performance.
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Old Today, 06:59 AM   #16
gerhard is offline gerhard  Germany
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like this shitty electrolytic in my paper above?
Manufacturer is Murata btw.

OMG,
Gerhard
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