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Well, I don't have any pictures for but have experienced all sorts of resistor issues over the decades. Mostly the issue is excess noise but microphonics happen also. Carbon composition resistors are the worst things going because they are both noisy and microphonic. Metal films are usually the best. One way to think about carbon resistors is to consider telephone "transmitters": the thing you speak into. Essentually the active piece is a carbon resistor.
Maybe your friend should read a little rather than just looking at the pictures?
Hello Rick. Do you happen to know ofa sources describing excess noise in detail? I seem to recall that excess noise is voltage dependent but at line levels probably insignificant whereas at speaker signal levels perhaps a factor...Plenty out thee about shot, thermal, popcorn etc but not much describing "excess". Maybe I'm just using the wrong keyword in my searching.
"Excess noise" is simply everything else beyond the (4kTRB)^1/2 thermal noise voltage.
It's just of a way of thinking about noise and keeping score. You can't avoid the thermal noise but you can work on the noise in "excess" of that such as the crud from micro-arcs in carbon comp. resistors.
Ah. Your wording helps clear up a lot for me. It makes sense that micro arcing would be more pronounced with technologies using a depositing or sputtering process to form the conductive paths. I suppose it's difficult to really characterize this problem generally since it must have much to do with specific manufacturing process and materials.
Very interesting. Thanks for the explanation. I'd previously come across a fellows webpage briefly mentioning "contact" noise within conductors/ resistors etc. caused from micro arcing from voids and impurities. One co-worker/mentor of mine has used the term "Excess noise" and didn't explain it to me. Good to finally sort of tie these loose ends into a slightly neater bundle.
Actually resistors do measure quite differently. Vishay has released several PDF files on this comparing the different types. carbon comps are usually noisier but do have a nice tonal quality to them. Carbon film are a bit quieter, next are metal film, then lower noise than metal film are wire wound. Metal foil are the quietest of the resistor types, but few if any mfgrs use all 100% metal foil resistors since the cost is so high.
Well, we agree...
I didn't mention metal foil because I don't have any experience with them.
Resistors are like any other passive: despite what we call them they are all multi-pole, temperature (actually radiation in general), Vib. frequency and level sensitive networks.
But that makes their names ackward so we cut corners and just refer to them by their hopefully dominant characteristic, the item that we WISH was their only feature!
Actually once in a while you can cash-in on more than one like using WW power resistors as Q reduced RF chokes. But not very often...
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