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I've been reading online discussions of audio electronics for years, and one of the truisms I've read over and over again is: ceramic capacitors are BAD and should be avoided.
It brings to mind a conversation I heard a few months ago where it was mentioned that you rarely hear people say that they hate dogs. I brought up the fact that you do hear people say that they either love or hate certain breeds of dogs chihuahuas--or pit bulls, etc....
In that context, I always wonder why so many people seem to be unable to distinguish between the different types of ceramic capacitors.
For example, Class 1 ceramics, variously described as C0G, NP0, etc... (a zero, not n 'O')
1) Are extremely stable with temperature (i.e., zero value change)
2) Suffer little to no aging effects
3) Do not exhibit changing capacitance with applied voltage
4) Are not piezoelectric (any more than any capacitor)
5) Are second only to polystyrene in terms of distortion at audio frequencies
6) Are similar to silver mica in almost every way--except that they cost about 1/20th as much
The rebuttal to this has usually been, "Yes, but they are only available in values of 100pf and less." That used to be true, but check your parts catalogs, and you'll find them in much larger values, due in part to multilayer construction.
Class II ceramics like X7R and Z5U have fundamentally different dielectrics. They are "doped" with things like barium titanate to achieve greater capacitance in a smaller package, and they are responsible for the bad reputation of ceramic caps in audio. They do exhibit variations in capacitance and DF with applied voltage and temperature. They do deteriorate with age, even if not used. They can be piezoelectric (due to the doping materials). They do produce measurable distortion at audio frequencies. And I'm not making this up; most of this is information you can find on the datasheets published by the companies that manufacture these capacitors.
If you do a search on this forum on the word 'ceramic,' you'll easily find 100 threads--I'm not sure if that's the search limit--mentioning ceramic capacitors. Search for C0G or NP0, and you find three, all of which appeared within the last two years.
All I'm suggesting is that it could be useful to learn to distinguish between the different types, especially if you need a stable, small capacitance value near a hot tube--or if you want to replace some Z5Us or X7Rs at a lower cost than mica.
Still, I have a client with a Supro amp full of Z5U ceramics, and he loves it. I guess 30 wrongs do somehow make a right ;-)
It brings to mind a conversation I heard a few months ago where it was mentioned that you rarely hear people say that they hate dogs. I brought up the fact that you do hear people say that they either love or hate certain breeds of dogs chihuahuas--or pit bulls, etc....
In that context, I always wonder why so many people seem to be unable to distinguish between the different types of ceramic capacitors.
For example, Class 1 ceramics, variously described as C0G, NP0, etc... (a zero, not n 'O')
1) Are extremely stable with temperature (i.e., zero value change)
2) Suffer little to no aging effects
3) Do not exhibit changing capacitance with applied voltage
4) Are not piezoelectric (any more than any capacitor)
5) Are second only to polystyrene in terms of distortion at audio frequencies
6) Are similar to silver mica in almost every way--except that they cost about 1/20th as much
The rebuttal to this has usually been, "Yes, but they are only available in values of 100pf and less." That used to be true, but check your parts catalogs, and you'll find them in much larger values, due in part to multilayer construction.
Class II ceramics like X7R and Z5U have fundamentally different dielectrics. They are "doped" with things like barium titanate to achieve greater capacitance in a smaller package, and they are responsible for the bad reputation of ceramic caps in audio. They do exhibit variations in capacitance and DF with applied voltage and temperature. They do deteriorate with age, even if not used. They can be piezoelectric (due to the doping materials). They do produce measurable distortion at audio frequencies. And I'm not making this up; most of this is information you can find on the datasheets published by the companies that manufacture these capacitors.
If you do a search on this forum on the word 'ceramic,' you'll easily find 100 threads--I'm not sure if that's the search limit--mentioning ceramic capacitors. Search for C0G or NP0, and you find three, all of which appeared within the last two years.
All I'm suggesting is that it could be useful to learn to distinguish between the different types, especially if you need a stable, small capacitance value near a hot tube--or if you want to replace some Z5Us or X7Rs at a lower cost than mica.
Still, I have a client with a Supro amp full of Z5U ceramics, and he loves it. I guess 30 wrongs do somehow make a right ;-)
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