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Capacitor type in low pass filter

ajmartin01

Feb 19, 2023
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Beginning to build a sine wave generator for 1KHz sine to test amplifier circuits for distortion. I have several examples I will be working from. The idea is to have ultra low distortion in the 0.005 or better range. My question is in the low pass filter of the Op Amp circuit what is the best capacitor type , Ceramic, mica, Polyester film? Yes I know the choice of Op Amp is critical for low distortion, I have several Burr Brown op amps that will more than meet the spec, so really the question is strictly about the capacitor.

Thanks for reading!

Alan
 

Harald Kapp

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(Almost) anything but no electrolytic. Don't even think of it.
[Edit] When using MLCCS, note that these can show piezoelectric effects. In this article the "singing" of ceramic capacitors is described. There is also the inverse effect: mechanical stress can induce voltages in this type of capacitors which will show up in the output of the filter. You may want to avoid this effect by using film capacitors.
 

ajmartin01

Feb 19, 2023
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Ceramic and mica are generally reserved for higher frequencies than the kHz range - you will be limited by the absolute minimum values required which will take you into the polyester, polypropylene, MLCC types.

Check this out:

Great article, very close to one of the circuits I was going to be working from. I was in fact going to NOT use the lamp you see in many of these circuits and use another approach. After reading this article I will start with the lamp idea and experiment from there. The answer to the capacitor question is Polypropylene film. Thanks much!

Alan
 

JRA

Jul 30, 2023
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The top-tier capacitor is probably polystyrene used for excellent stability, low noise, low leakage, etc. Used a lot in RF. They lost some favor over the years due to not being compatible with auto-insertion and their limited range of values but with low tolerance rating. But you will still see them in highly critical audio circuits like phono cartridge RIAA EQ circuits and the like, hand stuffed and hand soldered, 1-2% tolerance. Here's a selection of surplus polystyrene caps. Just scroll until you find the 0.005uF Mallory:


That one is a 5% but one can "build" lower tolerance by paralleling 1 or 2% values. Just FYI.
 

Delta Prime

Jul 29, 2020
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The top-tier capacitor is probably polystyrene used for excellent stability, low noise, low leakage, etc. Used a lot in RF. They lost some favor over the years due to not being compatible with auto-insertion and their limited range of values but with low tolerance rating. But you will still see them in highly critical audio circuits like phono cartridge RIAA EQ circuits and the like, hand stuffed
You're stuffed!
Electronic industry alliance (EIA)
& ECA dictate standards makes all the rules for capacitors.
RIAA recording industry association of America hase nothing to do with polystyrene capacitors.
polystyrene capacitors are very popular with manufacturers robotic pick and place machines because there general purpose.
RIAA equalization.
You forgot curve!
It's a format.
How you cut the grooves (dimensions of) in vinyl records so you can hear them in stereo
Bozo!
 

JRA

Jul 30, 2023
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You're stuffed!
Electronic industry alliance (EIA)
& ECA dictate standards makes all the rules for capacitors.
RIAA recording industry association of America hase nothing to do with polystyrene capacitors.
polystyrene capacitors are very popular with manufacturers robotic pick and place machines because there general purpose.
RIAA equalization.
You forgot curve!
It's a format.
How you cut the grooves (dimensions of) in vinyl records so you can hear them in stereo
Bozo!
What planet do you live on? Your reply makes no sense and is just wrong. You've got "polystyrene" mixed up with some other dielectric that maybe sounds or spells similar. Legacy polystyrenes are not auto-placed as most all are axial. And why are you associating the RIAA phono playback curve and "grooves" so vehemently with my use of that application as an EXAMPLE. Read this and back off.

 

JRA

Jul 30, 2023
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AnalogKid

Jun 10, 2015
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Beginning to build a sine wave generator for 1KHz sine to test amplifier circuits for distortion.

Page 26 is an article on how to design a very low distortion sine wave oscillator. If that is not on point, what did I miss?

ak
 

Delta Prime

Jul 29, 2020
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And why are you associating the RIAA phono playback curve and "grooves" so vehemently with my use of that application as an EXAMPLE. Read this and back off
First of all apologies I thought you were very poor AI salesman.
But I was incorrect you're not AI.
The use of the application as an example are located in my personal library they're called books but I'm certain this site will confirm although I never visited it. Don't need too.
 
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Delta Prime

Jul 29, 2020
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And I am no audiophile nor claim to be. I just hope you don't recommend oxygen free speaker wire. :)
 

JRA

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Page 26 is an article on how to design a very low distortion sine wave oscillator. If that is not on point, what did I miss?

ak
My original reply was
Page 26 is an article on how to design a very low distortion sine wave oscillator. If that is not on point, what did I miss?

ak
If you read your original post you were asking about the best 0.005uF cap technology for a low pass filter and I answered your question = polystyrene and I told you where to get them. The only thing "better" could be Teflon. I had no intention of discussing anything at all about the overall design. Maybe I thought your reply was in direct response to my reply so I missed that. I'm new here.
 

JRA

Jul 30, 2023
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And I am no audiophile nor claim to be. I just hope you don't recommend oxygen free speaker wire. :)
Won't do that and I won't recommend "Tip-toes" or exotic power cords either. I would though tend to poo-poo CCA (copper-clad aluminum) speaker wire. I'm a retired EE but only a wanna-be audiophile and tinkerer.
 

Delta Prime

Jul 29, 2020
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I'm a retired EE but only a wanna-be audiophile and tinkerer
EE Electrical Engineer. Engineer is derived from the word ingenious. I understand you're being facetious cuz an audiophile would be a downgrade. And who doesn't like to tinker. :)
On a different note.
Sorry I plowed into you like that.:(
 
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AnalogKid

Jun 10, 2015
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JRA - My post #8 was a response to the TS, not to you. In an open thread format like this site, keeping track of who is responding to whom can get confusing.

ak
 

AnalogKid

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EE Electrical Engineer. Engineer is derived from the word ingenious.

No, it is derived from the word enginour (“one who designs, constructs, or operates military works for attack or defense, etc.; machine designer”.

Later, it became associated with engines; specifically, coal-fired steam engines in factories and, yup, trains. As a parallel example, a mountaineer is someone who deals with mountains.


ak
 
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