On 9/27/09, misterb74 put forth:
used for power supply decoupling and op-amp compensation, and film
caps are used for everything else.
Ceramic caps are generally selected for low inductance or small
values. Overall they have poor tolerance and temperature stability,
so they are not suited for building a filters at a specific
frequency. However, if for some reason you need better quality in a
small value, or small size at a high voltage, there are better grades
of ceramic caps, as well as other alternatives, but they are much
more expensive.
Film capacitors, while having higher inductance, are available in
larger values and have properties more suitable for a wider range of
applications. Although most metalized polyester capacitors are crap,
in many cases crap is good enough. However, there are polyester caps
using hybrid dielectrics, often called coated polyester, such as
Panasonic ECQ or AVX BF/BQ, which are better. I've used both of them
for audio coupling. If you have the room, polypropylene has lower
DA, making it better for audio coupling, but it's overkill for most
synth modules.
Overall, selecting film capacitors for synth use is not that critical
with two exceptions. The first is in oscillator and timing circuits.
For example, high temperature stability would be important for a VCO.
The second is when building audio filters designed to have a
particular sound, such as a VCF clone.
of a half-assed convention to distinguish them from film caps of the
same value. Regardless, you don't want to use film caps to decouple
the power supply because their inductance to too high to form an
adequate filter. Z5U is fine, as temperature stability and tolerance
aren't important here.
Unless it is an critical application, it's generally safe to assume
that any capacitor as small a value as 47 pF is ceramic.
Also, Wima is a brand, not a type. They make a multitude of
different caps in the same values, although I'm guessing people are
talking about their MKS4 series, which aren't ideal for audio, but
most likely adequate.
>Hi there,It makes a difference. The short answer is that ceramic caps are
>
>I'm in the process of putting together digital noise and tube vca
>modules, but I'm fairly new to this hobby and am a bit confused
>about the appropriate capacitors to use. I'd appreciate some advice.
>
>When would a ceramic capacitor and when would a metalized polyester
>capacitor be more appropriate, or does it makes much of a difference?
used for power supply decoupling and op-amp compensation, and film
caps are used for everything else.
Ceramic caps are generally selected for low inductance or small
values. Overall they have poor tolerance and temperature stability,
so they are not suited for building a filters at a specific
frequency. However, if for some reason you need better quality in a
small value, or small size at a high voltage, there are better grades
of ceramic caps, as well as other alternatives, but they are much
more expensive.
Film capacitors, while having higher inductance, are available in
larger values and have properties more suitable for a wider range of
applications. Although most metalized polyester capacitors are crap,
in many cases crap is good enough. However, there are polyester caps
using hybrid dielectrics, often called coated polyester, such as
Panasonic ECQ or AVX BF/BQ, which are better. I've used both of them
for audio coupling. If you have the room, polypropylene has lower
DA, making it better for audio coupling, but it's overkill for most
synth modules.
Overall, selecting film capacitors for synth use is not that critical
with two exceptions. The first is in oscillator and timing circuits.
For example, high temperature stability would be important for a VCO.
The second is when building audio filters designed to have a
particular sound, such as a VCF clone.
>Based on the photos of assembled boards I'm assuming that the 100nIn the U.S., 100nF ceramic caps are often called .1uF, which is sort
>caps on the tube vca board are wima types (which I've been told are
>ideal for audio path type applications), and the 47 pf caps are
>regular ceramic. I'm less sure about the digital noise board.
of a half-assed convention to distinguish them from film caps of the
same value. Regardless, you don't want to use film caps to decouple
the power supply because their inductance to too high to form an
adequate filter. Z5U is fine, as temperature stability and tolerance
aren't important here.
Unless it is an critical application, it's generally safe to assume
that any capacitor as small a value as 47 pF is ceramic.
Also, Wima is a brand, not a type. They make a multitude of
different caps in the same values, although I'm guessing people are
talking about their MKS4 series, which aren't ideal for audio, but
most likely adequate.