Choose capacitor types to optimize PC sound quality

[PeteS in CA]

Choose capacitor types to optimize PC sound quality
A key challenge to designers of audio subsystems that must conform to Windows Vista requirements may be choosing coupling capacitors. These devices' capacitance varies with the voltage across them and introduces audio distortion. To minimize the effect, start by understanding the interactions among the dielectric material, voltage rating, device size, and voltage coefficient. Then, get ready to make trade-offs.
By Kymberly Schmidt, Maxim Integrated Products -- EDN, 4/12/2007

Passive components are critical to a successful audio design; they define gain, provide biasing, reject power-supply noise, and establish dc blocking between stages. Unfortunately, portable audio devices' space, height, and cost restrictions force the use of passive components with small footprints, low profiles, and low cost. Failure to understand the nonlinearity associated with these small, low-cost, passive components can affect Vista compliance (Reference 1).

Voltage coefficient, temperature coefficient, piezoelectric effect, equivalent-series resistance, equivalent-series inductance, leakage current, dielectric absorption, and tolerance describe how a capacitor's behavior deviates from ideal. The terms most important to understand when you design a signal path for premium audio performance are voltage coefficient and converse piezoelectric effect, which is the main contributor to voltage coefficient.

This article and the linked charts discuss and illustrate one of the two major caveats in using ceramic capacitors (except for NOP/COG types). The other caveat, not discussed, is the tempco (NPO/COG doesn't vary with temperature; X7R varies some; most other types are almost scary). One interesting "message in the article is that if you use MLCCs, is that there is a benefit to using parts with a voltage rating that is greater than the circuit needs. Personally, I prefer polyester or polypropylene.

[Logistics]

Re: Choose capacitor types to optimize PC sound quality

This article is like looking at a lineup of some of the worst possible compact cars and deciding which one is marginally better.

[gonzo0815]

Re: Choose capacitor types to optimize PC sound quality

WOW, i could not expressed it better .
I have had just the same thoughts when reading this.

Using MLCC caps in audio circuits could only be an idear of the beancounters.
It is absolutely not new, that their capacitance is depending heavily from the applied voltage and frequency.