Thanks, KChrisie,
You confirmed that tantalum capacitors cause distortion in audio circuits.

Passive crossover networks in speaker systems use a capacitor in series with the tweeter as a highpass filter.
Cheap speakers use non-polar electrolytic capacitors and good speakers use film capacitors.

I have seen hundreds of speakers but have never seen tantalum capacitors in them.

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Uncle $crooge

 

1µF at 160Hz is 1kΩ which is larger than 600Ω, therefore the capacitor will have a higher voltage across it than the resistor and contribute to more distortion than it would at higher frequencies or if it were larger.

The standard test is the 3dB point which would result in less distortion than you have measured.

Oversizing the capacitor would reduce the distortion even further.

Try increasing the capacitor to 10µF and you can expect to see the distortion to be reduced by a factor of 10.

By the way can you even hear 0.016% distortion?

I doubt it, but you certainly can't hear 0.0016% distortion.

Somehow I think it's more cost effective to use electrolytics in most applications.

Suppose your amplifier has an impedance of 10k, therefore you require 796nF so we use a 1µF capacitor.

If we wanted low distortion then we wouldn't use a ceramic capacitor, we'd ideally go for metal film but I think it would be more economical if we used oversized electrolytic capacitor. We could use a much larger 10µF capacitor which would have negligible distortion and would be smaller and cheaper than the 1µF film capacitor.

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A larger capacitor value might take too long to charge and you would hear severe distortion until it is charged. You also might hear severe distortion for a while after the power is turned off.

I use 330nF film capacitors for all my audio coupling capacitors with an input impedance that allows them to pass the entire audio bandwidth. They cost only 13 cents each American.

Manufacturers are still playing the "lowest distortion" game.
National Semi has their LM4562 dual opamp that has only 0.00003% distortion. It shows that the circuit was designed properly.

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Uncle $crooge

 

You are correct. I generated 5Vrms output and then adjusted the frequency until 2.5Vrms was measured across the 600Ω resistor. Should have used 3.5Vrms for the -3db power point. But the test is still valid, even if the numbers are slightly inflated, as it showed that there is a difference in distortion generated by different dielectrics.
Yes, but SSMan was talking about filters and crossover networks. I think.
I can't. But once you use a bunch of crappy caps in a multipole filter I might. I certainly wouldn't use ceramic or tantalum caps in an equalizer.
I won't argue that point. Once the coupling cap is over sized, to say a 1Hz -3db highpass, then distortion becomes negligible in the 20Hz-20Khz audioband.

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Inside every little problem, is a big problem trying to get out.

 

True but if the capacitors are oversized by a factor of no more than about 10 for 20Hz, they should charge quickly enough to prevent that from being a problem.

For example the RC constant of 10µF and 10k is just 0.1s so it will charge to 95% in just 0.3s which you'll probably notice but is not long enough to be a big deal.

I don't know about in the US but here in the UK, a 3.3µF electrolytic costs half the price, is well under a quarter of the size and you probably won't be able to hear the difference.

Anything to make more money from silly audiophiles who'll pay twice as much for half the distortion that they can't hear anyway.

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If you want to hear 20Hz at the same level that it was recorded at (if your speakers go that low) then you want a flat response at 20Hz and a -3dB frequency of 4Hz.
If there are two coupling capacitors then the -3dB frequency becomes -6dB so the -3dB frequency of each section should be 2Hz.

If you increase the value of a coupling capacitor because it is the distorting kind then its time constant becomes 0.4 second which is a noticeable charge-up time.
Two sections each would have a 0.8 second charge-up time

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Uncle $crooge

 

So using your logic you need 10µF capacitor if you have two 10k stages, those 10µF metal film capacitors are going to be pretty bulky and expensive.

Why would you worry about distortion for frequencies below 20Hz?

The capacitors will all charge at the same time, not one after the other.

Seriously, a 10µF capacitor is fine for a 10k input impedance.

The only time metal film cacitors are useful are in crossovers and filters where you don't want to chance the cut-off frequency.

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I don't use an input impedance as low as 10k ohms. I use 120k so that I can use a very good, small and inexpensive 330nF film input capacitor.

Many products use cheap electrolytic coupling capacitors. They deform and become useless if they don't have a DC voltage across them.

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Uncle $crooge

 

I agree, make the input impedance as high as possible but sometimes you don't have a choice.

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