non inductive capacitors. Is this something to look for?

[ssstonelover]

I came across the term 'non-inductive' capacitor today for the first time and after checking on the web found it (or low inductance capacitor) exist, and can be purchased in actuality.

As I've never heard of inductance and capacitor in the same sentence before, I wonder if this is something we really need to worry about in guitars and if any such inductance is masked or overwhelmed by other sources of inductance in the circuit, or if by their nature most caps are low or no-inductance anyway.

Please weigh in on this and educate me, thanks!

[sumgai]

Bethany,


ChrisK would have only two words for you: MarketingSpeak Is.

He might also have gotten all wordy and said: Gefooey, or GelderFarb, or other similar dismissive phrases.

In short, all components have and can be made to exhibit, capacitance, inductance and resistance. Let me repeat that: ALL COMPONENTS, ACTIVE OR PASSIVE. The real test is whether or not such properties are measurable in some sense, in any given use case.

For our purposes, we can very safely ignore anything in the way of inductance in our capacitors.  Worrying over such is folly, if for no other reason that any value of inductance we might find (which would require laboratory-grade test equipment) would be swamped by that of the pickup coils themselves, end of story.  Even the cheapest capacitors we might purchase for installation will have a vanishingly small inductance value, compared to those coils.  

Last Word: (paraphrasing ChrisK here)  Someone is always the sucker.  Make sure it's not you!

HTH



sumgai

[ssstonelover]

Thanks Sumgai. I'm glad I asked the question.
More marketing voodoo drivel that doesn't do anything, or rather misdirects and adds cost without functional improvement.

[reTrEaD]

Jan 1, 2024 16:22:06 GMT -5 ssstonelover said:

I wonder if this is something we really need to worry about in guitars

In guitars, no. In power supplies with huge electrolytic capacitors, YES.

[ssstonelover]

Excellent, thanks

[kitwn]

I'm with sumgai on this. So much hype and gobbledegook (another excellent word) intended to part the unknowing from their hard-earned cash.

If you were building a radio-frequency device, especially one with some power behind it, then the inevitable inductance that is in every piece of wire could become significant but in a guitar we have the simplicity of working at very low power and (in overall electronics-world speak) very low frequencies.

Should you wish to dig further into capacitor specifications the 'self-resonant frequency' tells you where the capacitive reactance (the bit you think you're buying) and the unavoidable inductive reactance that comes with it are equal in value. Above that frequency the capacitor actually behaves as an inductor. As long as this frequency is well above your working range then there is no problem.

For example, a common 22nF film capacitor you might choose for a tone circuit and available for about US$1 has a self-resonant frequency of approx 1MHz. That's more than 'non inductive' enough for our needs. And it's an orange blob, so it must be good!🤣

Kit

Ref:https://au.rs-online.com/web/p/film-capacitors/0115247