Hello.
I am wondering if I should be concerned in using a rc filter right at the input ? Also I want only real measurable fact no feelings or blind test data.
Also does the amount of capacitance matter for something else than setting the -3db point ?
Thank you in advance.
I am wondering if I should be concerned in using a rc filter right at the input ? Also I want only real measurable fact no feelings or blind test data.
Also does the amount of capacitance matter for something else than setting the -3db point ?
Thank you in advance.
For a high pass filter at the preamp or power amp input, there will be protection from DC inputs.
For a phono stage, there will be attenuation of record warps and the 10Hz LF resonance.
Some degradation of the sound may occur, depending on which capacitor is used.
If the source has an output capacitor, a redundant input capacitor is not needed.
Yes, f = 1/ (2Pi xRC) applies. The R should include the source resistance and the entire load resistance.
For a phono stage, there will be attenuation of record warps and the 10Hz LF resonance.
Some degradation of the sound may occur, depending on which capacitor is used.
If the source has an output capacitor, a redundant input capacitor is not needed.
Yes, f = 1/ (2Pi xRC) applies. The R should include the source resistance and the entire load resistance.
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Thank you rayma. Do you know if maximizing the capacitance to get the largest frequency response (lower -3db) has any adverse effect ?
I mean i could use a 220nf or a 22nf and i would still have lower than 10hz cut point. But does the bigger capacitance is harmful or beneficial ?
I mean i could use a 220nf or a 22nf and i would still have lower than 10hz cut point. But does the bigger capacitance is harmful or beneficial ?
For other than a phono input, electrolytic capacitor distortion and phase shift is reduced by designing
for ~2Hz high pass. For example with a 10k input impedance, this means a 10uF capacitor.
Nichicon UES bipolar electrolytic types work very well for this purpose.
https://www.nichicon.co.jp/english/products/pdfs/e-ues.pdf
Film capacitors tend to be better when a smaller uF, and a higher voltage rating, is chosen.
They do not need to be oversized to reduce their distortion, like electrolytic types require.
Polypropylene film types are preferred, and polyester (Mylar) film types should be avoided.
In general however, a circuit's LF corner should be set by just one dominant time constant.
Other LF time constants should be set at least several times lower in frequency.
This will audibly improve the bass response, due to smaller nonlinear LF phase shift.
for ~2Hz high pass. For example with a 10k input impedance, this means a 10uF capacitor.
Nichicon UES bipolar electrolytic types work very well for this purpose.
https://www.nichicon.co.jp/english/products/pdfs/e-ues.pdf
Film capacitors tend to be better when a smaller uF, and a higher voltage rating, is chosen.
They do not need to be oversized to reduce their distortion, like electrolytic types require.
Polypropylene film types are preferred, and polyester (Mylar) film types should be avoided.
In general however, a circuit's LF corner should be set by just one dominant time constant.
Other LF time constants should be set at least several times lower in frequency.
This will audibly improve the bass response, due to smaller nonlinear LF phase shift.
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Thank you. Do you think film are better in higher voltage rating because of the thicker foil conductor ?
I recently ordered a bunch of 10uf ceramic capacitor for input coupling purpose. Sometimes, polypropylene types take too much footprint to be practical.
Most film capacitors are metallized, not foil. Their metallization is actually very thin, so they are
much more limited in current capability than foil types.
Higher voltage film capacitors are better than lower voltage film types, due to their thicker dielectric.
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Unfortunately, the preferred NPO/COG ceramic dielectric is not available in capacitors greater than 0.1uF.
A 10uF polypropylene capacitor would be physically large, even for lower voltage ratings. However,
they are still often used in loudspeaker crossovers, where size is not as important.
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I think ceramic should be perfectly suitable and in the input there is very low chance of having this capacitor heat up and add distortion by lowering value (for class 2), also dc bias is also inexistent most of the time in the input. so it should be suitable. Thank you for this because ceramic a quite small and i was asking because i wanted to save space by removing this cap in my build!
Thank you rayma you are always a good help on this forum ! I will follow your advices and go for higher voltage film caps.
Thank you rayma you are always a good help on this forum ! I will follow your advices and go for higher voltage film caps.
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Only COG/NPO ceramic capacitor types are suitable for audio, since other ceramic dielectric
types (X7R, Y5V, Z5U, etc.) have measurably high distortion.
Film capacitors with extended foil construction will have much lower parasitic inductance, and
better high frequency behavior.
types (X7R, Y5V, Z5U, etc.) have measurably high distortion.
Film capacitors with extended foil construction will have much lower parasitic inductance, and
better high frequency behavior.
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