Bad capacitors in audio
I don't know if this is considered on topic - this site is called badcaps, but is mainly about electrolytic capacitors causing malfunction in power circuits due to high ESR. I didn't find any references to "Bateman", or any likely hits with "distortion", so maybe this has not been discussed, or is so familiar to everyone that it's never discussed.
In audio circuits capacitors of all sorts can produce distortion. Ceramic capacitors, as a class, have a particularly bad reputation, but this seems to be largely mythical. I don't know how audible these effects are (most claims are subjective), but some very detailed measurements were made in the early 1990s, finding distortion due to capacitors to be significant and measurable. A series of articles was published by C Bateman: http://www.scribd.com/doc/2610442/Capacitor-Sound . Identified as myths: all ceramic capacitors distort; dielectric absorption causes (audio) smearing and compresses dynamic range; polypropylene is an efficient material; ESR of a capacitor has a fixed value.
The 1992 results suggested that the lowest-distortion types up to 10nF were C0G ceramic (not all ceramic), extended foil/polystyrene or extended foil/polypropylene, with the lead-out wires soldered to the electrodes. PET capacitors are very variable, often with large distortion. Metallised film should be avoided. A particular 100nF ceramic disc capacitor type had about the worst distortion. Specific capacitor ranges were mentioned; I don't know if there is more recent information on current types.
Electrolytics distorted more, varying from one make to another and with bias voltage. Tantalum beads were 10 times worse than aluminium. For all these measurement absolute distortion was not a large figure; 0.004% (for a single capacitor) was considered very bad. Shunting an electrolytic with a lower-distortion type of lower capacitance produced insignificant benefit. The author considered that use of a 100 microfarad electrolytic in the signal path of an audio amplifier was never a good idea.
ESR was not considered in detail; one test was made on 100 microfarad/10V electrolytics with ESR from 0.012 to 0.5 ohms. The low-ESR one produced nearly twice as much distortion with DC bias, 10 times more when unbiased (unbiased always produces less distortion).
I won't go on, the articles speak for themselves. If anyone is interested the topic can be discussed further; there's not a lot I can say, other than parroting Bateman.
Maybe the badcaps organisation can branch out into selling certified low-distortion capacitors?
I don't know if this is considered on topic - this site is called badcaps, but is mainly about electrolytic capacitors causing malfunction in power circuits due to high ESR. I didn't find any references to "Bateman", or any likely hits with "distortion", so maybe this has not been discussed, or is so familiar to everyone that it's never discussed.
In audio circuits capacitors of all sorts can produce distortion. Ceramic capacitors, as a class, have a particularly bad reputation, but this seems to be largely mythical. I don't know how audible these effects are (most claims are subjective), but some very detailed measurements were made in the early 1990s, finding distortion due to capacitors to be significant and measurable. A series of articles was published by C Bateman: http://www.scribd.com/doc/2610442/Capacitor-Sound . Identified as myths: all ceramic capacitors distort; dielectric absorption causes (audio) smearing and compresses dynamic range; polypropylene is an efficient material; ESR of a capacitor has a fixed value.
The 1992 results suggested that the lowest-distortion types up to 10nF were C0G ceramic (not all ceramic), extended foil/polystyrene or extended foil/polypropylene, with the lead-out wires soldered to the electrodes. PET capacitors are very variable, often with large distortion. Metallised film should be avoided. A particular 100nF ceramic disc capacitor type had about the worst distortion. Specific capacitor ranges were mentioned; I don't know if there is more recent information on current types.
Electrolytics distorted more, varying from one make to another and with bias voltage. Tantalum beads were 10 times worse than aluminium. For all these measurement absolute distortion was not a large figure; 0.004% (for a single capacitor) was considered very bad. Shunting an electrolytic with a lower-distortion type of lower capacitance produced insignificant benefit. The author considered that use of a 100 microfarad electrolytic in the signal path of an audio amplifier was never a good idea.
ESR was not considered in detail; one test was made on 100 microfarad/10V electrolytics with ESR from 0.012 to 0.5 ohms. The low-ESR one produced nearly twice as much distortion with DC bias, 10 times more when unbiased (unbiased always produces less distortion).
I won't go on, the articles speak for themselves. If anyone is interested the topic can be discussed further; there's not a lot I can say, other than parroting Bateman.
Maybe the badcaps organisation can branch out into selling certified low-distortion capacitors?
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