I am working on a new build (Muffin Fuzz, Triangle), and I decided that it was time to learn something about capacitors. I always struggle the most when picking out capacitors. Which ones to get? For example, this build calls for 4n capacitors. The PCB layout suggests that these should be electrolytic, but I can't seem to find any in that value.
Another question: does polarity always matter? I have seen non-polarized box capacitors used on PCBs that call for a polarized capacitor.
So is there a rule or trick to knowing which capacitors to get? Or is it one of those things that you just have to figure out?...
I finished 2 Big Muff pedals a couple of weeks ago. A Violet Rams head and a Triangle. With the triangle variant, the only polarized cap is the 100uF (C14) in the power supply stage.
Caps are a funny breed. If you notice, with the pedal circuits they come in 3 flavors most of the time. Micro-farads (uF), nano-farads (nF) and pico-farads (pF). uF = .000001F, nF=.000000001F, and pF=.000000000001F. So say 47pF would equal .000000000047 Farads.
The pico=farads are the smallest values and normally come in ceramic disc or MLCC. MLCC are a better quality and last longer, ceramic disc are cheaper. Do yourself a favor and look for the MLCC first.
So next is nano-Farads, Higher value capacitance so the caps start getting bigger. 1nF to 1uF look for the box film caps. These have a lower noise level and caps this size are normally (but not always) in the signal path.
Now we come to uF. This is where the polarized caps come in. You'll notice that around 220nF the size of the box caps start to get bigger, for the same voltage rating. By the time you get to 1uF 100V the box caps are much bigger and toke up space. This is where they switch to polarized caps, which are quite small at 1uF 50V. Tantllums caps are also an option here these also also polarized. When using either of these you have to pay attention to the voltage polarity and ensure the + lead is connected to the higher DC value side in the circuit. Thais why you see the square pad on these. Which should take the longer lead, but always check your polarity on these caps to ensure they don't pop when applying power.
As for interchanging caps , yes you can. Just make sure the capacitance is the same for both caps, and if you are putting in a polarized cap for a film then make sure the polarity of the polarized cap is correct against the schematic..
There is overlap between the cap values and types, which is a good thing. For the triangle build there are 50nF caps (C5 and C8) used before the clipping diodes. 50nF is not a common value anymore. To get the 50nF I used 2 100nF MLCC caps and placed them in series, which is 50nF. Search for capacitance in series and parallel if you need to know more on this as its a lesson in it's self.