Capacitor Differences for Pedals - Film or Ceramic?

[timd]

What are the differences between ceramic and film capacitors for a build if the values are the same? The reason I ask this is that I have seen some builds specify a certain capacitor type. Also, I use a multimeter to test caps against their printed value for quality control and noticed that ceramic caps take a lot longer to test than film caps. Why is that?

[senko]

There are tonal differences that a capacitor's material can contribute to.  I'd suggest first getting your project together with cheap parts, then start substituting in the more expensive ones if they sound better.  I've found ICs and transistors contribute more to a pedal's sound than something simple like a high value capacitor.

[alexradium]

Not so much difference from ceramic to polyester in a pedal,maybe the former is a little faster and stiff.
I experienced much more difference from film to electrolytic to tantalum when used as a coupling cap especially in the last stage,electros sound fuller to me

[amptramp]

There are several ways that capacitors can change the sound, assuming there is negligible leakage and series resistance.

Imagine a vacuum capacitor where the charges are lined up on opposing plates.  When the voltage is removed, the charge goes away.  Now add a dielectric between the plates and imagine it has a polar molecule for the dielectric, one where the melecule of the dielectric has a positive and a negative side (like water).  You apply a charge and the molecules rotate into position so the positive of the dielectric molecule lines up with the negative plate of the capacitor.  Then remove the charge by shorting the capacitor leads.  The molecules will return to random positioning with many dielectrics but not others.  You can charge a capacitor, short the leads, separate the leads and measure a voltage across them.  This is called dielectric absorption and it creates a hysteresis - a memory effect that causes the capacitor to remember former states (which it should not do).  Charge distribution in this case is like an electret, the electrostatic counterpart to a permanent magnet.  Film capacitors generally have very little dielectric absorption.

With ceramic, you have plenty of dielectric absorption plus the extra effect of piezoelectricity which causes the capacitor to deform mechanically with applied voltage, acting like a piezoelectric speaker.  And conversely, the ceramic capacitor may act like a piezoelectric microphone, picking up sounds and adding them to the signal.  You may find strange effects happening in concert at 110 db sound levels that you cannot reproduce when testing the pedal in your bedroom / laboratory / studio.  I generally stay away from ceramic capacitors for audio.  However, you may like the non-linear effects of ceramic for certain purposes - just don't produce a run of pedals and expect consistency in these effects.  Voltage out = voltage in - voltage absorbed in flexing the dielectric for the first effect and voltage out + voltage in + microphonic voltage for the second.

[duck_arse]

go here:

http://diyaudioprojects.com/mirror/members.aol.com/sbench102/caps.html

and read. pictures included.

RG himself (on the tremvibe circuit) specifies a cap as "a" value, but "another" value for N.P. this has always bothered me whenever and wherever I see it. surely 240nF is 240nF no matter what the dielectric?

[Gus]

Look up NP0 C0G ceramic capacitors.  Not all ceramics are the same.

[timd]

I generally stay away from ceramic capacitors for audio.  However, you may like the non-linear effects of ceramic for certain purposes - just don't produce a run of pedals and expect consistency in these effects.  Voltage out = voltage in - voltage absorbed in flexing the dielectric for the first effect and voltage out + voltage in + microphonic voltage for the second.

I haven't seen many ceramics used in pedal builds before. I haven't been using them, but I have quite a stash and was wondering about. Thanks for the info.

[FiveseveN]

I haven't seen many ceramics used in pedal builds before.

Well then you haven't been looking hard enough
http://www.diystompboxes.com/smfforum/index.php?topic=73038.msg593158#msg593158
http://imageshack.us/photo/my-images/65/1989ds1guts1.jpg/sr=1
http://www.mattejat.de/MIJ2a.jpg
http://home.comcast.net/~snmavronis/mxr_distortion_plus_replica_pcb.jpg
(Granted, some of those are used in the bypass flip-flops.)

[alexradium]

I generally stay away from ceramic capacitors for audio.  However, you may like the non-linear effects of ceramic for certain purposes - just don't produce a run of pedals and expect consistency in these effects.  Voltage out = voltage in - voltage absorbed in flexing the dielectric for the first effect and voltage out + voltage in + microphonic voltage for the second.

I haven't seen many ceramics used in pedal builds before. I haven't been using them, but I have quite a stash and was wondering about. Thanks for the info.

funny enough,Xotic/EWS pedals are all the way on every pro pedalboard i've seen in the last 7 years,all of them use multilayer ceramic and electros

[Jdansti]

This was posted on another thread and looks like some good info.

http://web.archive.org/web/20030807122631/http://capacitors.com/picking_capacitors/pickcap.htm#intro

[bukas]

to me ceramic is a necessary evil and i try not to use them if possible

[timd]

This was posted on another thread and looks like some good info.

http://web.archive.org/web/20030807122631/http://capacitors.com/picking_capacitors/pickcap.htm#intro

Nice read. The article mentions the distortion issues and their philosophy that ceramics should never be used in audio situations. Let's just "assume" this statement is correct. Why then are they appearing in pedal builds? Are they just for parts of the circuit away from the audio path? Could it be a cost issue? Are some using the "distortion" of the ceramics to a pleasing effect? 

[bukas]

way i see it, its an issue of capacity of film capacitors, they don't get below 1nF. so when you see a ceramic capacitor in any respectable audio piece it can mean two things:
1 it is not part of audio circuit ( power section)
2 its capacity is below 1nF and as such it had to be used there

when you look at schematics you don't see a lot of caps under 1nF ( read ceramics)
problem with ceramics that i had, and many others as i understand, is that they pick up electromagnetic waves easily. this was not such a problem lets say 40 yrs ago when we had radio signal and TV signal and that was it. today we have signals coming from wifi router, wifi cards, cordless phones, mobile phones, bluetooth devices, radio etc, and problem is that ceramic cap is going to pick them up and make them audible in form of buzz,hiss and so on. this is why enclosure is important, its job is to prevent these signals getting to circuit. enclosure needs to be metal or any other material with cooper foil inside. but that is not enough because signals penetrate enclosures, so we use film caps which are much more resistant to electromagnetic waves than ceramic ones. does this change effect? i don't know. i will build two blues breakers using ceramics and film and post audio samples so you be judge

[EATyourGuitar]

watch this

[Jdansti]

I agree about the small cap values only being available in ceramics.

[EATyourGuitar]

way i see it, its an issue of capacity of film capacitors, they don't get below 1nF

I buy film box caps all the way down to 47pf in reasonable sizes for 63v or 50v. the biggest package is about 7.2mm x 4.5mm and less common 7.2mm x 5.5mm

manufacturers are kemet, wima, vishay

the smallest vikiin or epcos might be 1nf

[timd]

way i see it, its an issue of capacity of film capacitors, they don't get below 1nF. so when you see a ceramic capacitor in any respectable audio piece it can mean two things:
1 it is not part of audio circuit ( power section)
2 its capacity is below 1nF and as such it had to be used there

when you look at schematics you don't see a lot of caps under 1nF ( read ceramics)
problem with ceramics that i had, and many others as i understand, is that they pick up electromagnetic waves easily. this was not such a problem lets say 40 yrs ago when we had radio signal and TV signal and that was it. today we have signals coming from wifi router, wifi cards, cordless phones, mobile phones, bluetooth devices, radio etc, and problem is that ceramic cap is going to pick them up and make them audible in form of buzz,hiss and so on. this is why enclosure is important, its job is to prevent these signals getting to circuit. enclosure needs to be metal or any other material with cooper foil inside. but that is not enough because signals penetrate enclosures, so we use film caps which are much more resistant to electromagnetic waves than ceramic ones. does this change effect? i don't know. i will build two blues breakers using ceramics and film and post audio samples so you be judge

Great idea for an A/B comparison.

[amptramp]

I agree about the small cap values only being available in ceramics.

You can get small values in silver mica, which does not have the same problems as ceramic.

[Jdansti]

I agree about the small cap values only (edit: mostly) being available in ceramics.

[Thecomedian]

This was posted on another thread and looks like some good info.

http://web.archive.org/web/20030807122631/http://capacitors.com/picking_capacitors/pickcap.htm#intro

Nice read. The article mentions the distortion issues and their philosophy that ceramics should never be used in audio situations. Let's just "assume" this statement is correct. Why then are they appearing in pedal builds? Are they just for parts of the circuit away from the audio path? Could it be a cost issue? Are some using the "distortion" of the ceramics to a pleasing effect? 

production cost (silica is 60% of the earth crust), size, material stability.