What type of capacitors should I use?

[PearseSwail]

Hey guys,

I'm new in the wonderful world of pedal making... And I have the basic gist of it, however, I have no clue how to choose which capacitors to use...

I'm planning on building this- http://www.tonepad.com/getFile.asp?id=89 -but how can I tell what type of capacitors past the values? I see on the diagram which ones need to be electrolytic, but for the non-polarized caps does it matter if they're film or ceramic for this application?

Also, I'm assuming low voltage caps will suffice... But again, how can I know? 16V or 25V?

Thanks very much,

Pearse Swail

[italianguy63]

I've kind of wondered the same....

Is there a time where (box) film, mica, disc, or MLCC is preferred?  Of course, a disc is probably noisier.  But say, is there a time to use a "greenie" vs. a box film?

MC

[merlinb]

For guitar pedal work, it really doesn't matter. Any type will do. It matters more in hifi.
As for voltage rating, most of our circuits work at 9V, so it is a safe bet to use caps with a higher voltage rating than that. More than 20V is a good choice since it makes the pedal a bit more robust against accidentally (or deliberately!) plugging in a higher-voltage supply. There's no upper limit; heck, you can use 450V-rated caps if you want to (and can fit them in the box...  )

[R.G.]

Capacitor selection considerations:
1. Voltage: have to have enough.
2. Value: It has to be the right(ish) value. Capacitance value matters a lot where you're using it to discriminate frequencies or timing, not much at all for simply power bypassing.
3. Size: It has to fit on the board or other space for it.  This is the entire reason that electrolytics exist - they are scummy as capacitors, but they are very small for their voltage and capacitance ratings
4. Side effects: This is where everything else is balled up.

4a: some ceramics are piezo-microphonic
4b: different dielectrics (NPO, Y7R, Z5R, poly-mumble-ene, aluminum oxide, mylar, yada, yada) drift differently with temperature and time
4c: different dielectrics have different dielectric absorptions (if you design pedals that need to worry about this, you're in the wrong forum)
4d: distortion: distortion has been measured for electrolytics where there is significant AC voltage across the cap; for others, I have not see any info on capacitor distortion; another stake in the heart of electros
4e: power, pulse, and healing effects; the exact construction of the internal conductors and insulators matter when you're funneling in large currents at high rep rates and high voltages. You can overheat caps (I've done this, literally melted them down) by overdoing the currents flowing through them. Again, if you're doing pedals that need to worry about these effects, you're in the wrong forum.
4e: cork-sniffing effects - "Orange Drops", "tropical fish", "greenies", the list goes on. Oddly, this last, and least significant aspect of capacitors is what gets all the discussion.

Choosing caps: If you don't know the details of what I've listed, pick a cap that is electro or not as per the schematic, then get film (which includes dipped-epoxy greenies, redd-ies, yellow-ies, etc-ies, box film, etc.) for signal path, ceramic for signal bypass or very small values (under 100pF or so) and get NPO types for this. For power bypass, get monolithic ceramic, which will probably be MLCC these days, and probably Y7R or Z5R dielectric for small size. Disc is still good, but mostly this is a form factor, and is being pushed out in favor of the more rectangular shapes, except for voltage ratings in the hundreds and thousands.

Then listen to what you have. Does it work? If not, fix it. If it does, listen to the sound and see if you like it. If you don't like it, then go worrying about which exact flavor of caps to put in.

[PearseSwail]

Fantastic.

Thanks very much guys,

Pearse Swail

[midwayfair]

poly-mumble-ene

[armdnrdy]

This is what I use for capacitor selection:



As for voltage rating...it's kind of hit or miss. If I hit the board, I go with a smaller voltage. If I miss the board....a larger voltage.

I can honestly say that it has worked out very well so far.
All of my effects sound great! but....I think that it's kind of odd that some controls that are labeled "Delay Time" and "Resonance" on my analog delay and flanger actually control distortion.  

[italianguy63]

Geeezzz R.G.  Could have just given a simple "no."  LOL   

I put on what looks pretty sometimes... LOL

Reminds me of a story the 1st time I went to a horse-racing track.  I had a "SYSTEM" and placed my bets and lost.

My girlfriend at the time bet on the names of the horses betting on the horses with "pretty" names.  She won.

Go figure.

MC

[GibsonGM]

Great advice from all, ha ha   

I do prefer Tantapolyramicene  for most builds, tho....

[Jdansti]

Another consideration is availability and cost. I order almost all of my caps from Tayda. I generally get ceramics at $0.01 each for values under 1nF (1000pF).
http://www.taydaelectronics.com/capacitors/ceramic-disc-capacitors/test-group-2.html

For non-polar values of 1nF and greater, I get the poly box caps for $0.08-$0.20 each.
http://www.taydaelectronics.com/capacitors/polyester-film-box-type-capacitors.html
The poly-mylars are a little cheaper, but watch out for the size of the body and the lead spacing. The box caps are pretty uniform and fit most perf, vero, and manufactured PCBs.

Polar are generally aluminum electrolytic:
http://www.taydaelectronics.com/capacitors/electrolytic-capacitors.html unless tantalum is specified.

The ceramic and poly caps are almost always going to be rated >25V. Watch out for the electrolytic voltage ratings, though.

BTW-The current Tayda coupon code for 15% off is haribo and it's good through 6/22.

[digi2t]

This is what I use for capacitor selection:



As for voltage rating...it's kind of hit or miss. If I hit the board, I go with a smaller voltage. If I miss the board....a larger voltage.

I can honestly say that it has worked out very well so far.
All of my effects sound great! but....I think that it's kind of odd that some controls that are labeled "Delay Time" and "Resonance" on my analog delay and flanger actually control distortion.  

You gotta spin that sucker before throwin' the dart, or is it a "close yer eyes an' fling" kinda deal? Or does that depend on the application as well?

[bluebunny]

You gotta spin that sucker before throwin' the dart . . .

Dart?  Soldering iron!   

[Liquitone]

haha! that capacitor dartboard is brilliant!