Opinions on input/output cap values

[Chris60601]

Hi all

I need some advice please since I know many of you are far more technical in matters like this than I am.
I would like to know some potential values for input and/or output caps based on the following criteria.

Single Coil pickups:
1. allow full range of tone into pedal?
2. remove a little low end
3. allow a slightly brighter output

Humbucker pickups:
1. allow full range of tone into pedal?
2. remove a little low end
3. slightly more middle
4. brighter high end

Not worried about clipping options of overdrive/distortion, just concentrating on the values to achieve the above based on the values of either/or both the input and output caps.

Thanks in advance and cheers!

[Travis]

The frequency response of the input and output caps is dependent on impedance, so different circuits would use different values to get the same freq response. For that reason, you can't really suggest specific cap values for all builds

[Chris60601]

To be honest, I was hoping for a range of values. Perhaps what most folks use for whatever reason (technical or whimsical) . I understand that there is no one size fits all, but there are reasonable and somewhat standard (perhaps a poor choice of words) values that you see in many builds. For example, perhaps caps at .01, .022 etc.

Perhaps the questions is just too wide. So, what are some of the more common values found for both in/output caps.  This probably is a better way to ask.

[Travis]

A commonly used range of input and output cap values could be anything from like 4n7 to 10u

4n7 is the value for the input cap of the rangemaster and it cuts bass resulting in a upper mid and treble boosted sound.

2u2 is the input cap in the fuzz face and it allows a full range of frequencies in the front end.

With a dirt pedal, the input cap value can affect not only the freq response, but also the headroom of the circuit. If you cut a lot of bass like in the rangemaster, your guitar will appear weaker at the front of the circuit, and won't drive it as hard. If you're letting a full frequency range in, your guitar is about as powerful as possible to drive the front of the circuit. In a sense, larger input cap values allow for maximum dirt if nothing else is changed in a circuit.

The output cap on the other hand can be adjusted without altering the amount of dirt from the pedal. So you could cut bass with the output cap without losing dirt. It is pretty common for dirt pedals to allow a full range of frequencies to "hit" the front end for a fat, distorted sound, then cut some bass at the output to tighten up the sound without losing dirt.

Both the Fuzz Face and Rangemaster have 10n output caps. In the FF, this is cutting some bass which helps to avoid a muddy sound with some amps. I tend to up the output cap to 100n on the FF if I'm building it for a bass player.

A lot of people think the "MK1.5" Tone Bender is brighter than the Fuzz Face but the input cap on the MK1.5 is actually bigger. The big difference in that case is actually the volume pot value. The 500K in the FF lets lots of low end through, the 100K in the MK1.5 tightens up the low end. So the volume pot value also makes a difference since it is playing with the output impedance.

Basically as I said before it is impossible to generalize with the results of different values because the same cap value can have dramatically different responses depending on the rest of the circuit.

I'd say the most common input and output cap value is 100n. In something with high input impedance and low output impedance, it's common to see a smaller input cap value and a larger output cap value. This is usually done to achieve a flat response. The same values would have a completely different result in something like a Fuzz Face

Seems like I could ramble on forever, and basically spin in circles without ever landing on an answer because there is no definite answer. But I tried to do something lol

[Frank_NH]

"Basically as I said before it is impossible to generalize with the results of different values because the same cap value can have dramatically different responses depending on the rest of the circuit. "

Travis hit the nail on the head.  In simple terms, a capacitor in series with the input forms a high pass filter with whatever the impedance of the subsequent part of the circuit is (which could be anything from a transistor buffer to an op amp gain stage).  The larger the value, the more "low end" frequencies will be accentuated.  Like everything, experimenting (using a breadboard) can be very instructive.   If you are more into circuit design, I would highly recommend getting a learning to use a circuit simulator like LTSpice.  You can examine so many "what if" scenarios before you go to the breadboard and in turn get a better understanding of what effect different component substitutions make on the circuit.   

[Chris60601]

Travis wrote

A commonly used range of input and output cap values could be anything from like 4n7 to 10u

4n7 is the value for the input cap of the rangemaster and it cuts bass resulting in a upper mid and treble boosted sound.

2u2 is the input cap in the fuzz face and it allows a full range of frequencies in the front end.

With a dirt pedal, the input cap value can affect not only the freq response, but also the headroom of the circuit. If you cut a lot of bass like in the rangemaster, your guitar will appear weaker at the front of the circuit, and won't drive it as hard. If you're letting a full frequency range in, your guitar is about as powerful as possible to drive the front of the circuit. In a sense, larger input cap values allow for maximum dirt if nothing else is changed in a circuit.

The output cap on the other hand can be adjusted without altering the amount of dirt from the pedal. So you could cut bass with the output cap without losing dirt. It is pretty common for dirt pedals to allow a full range of frequencies to "hit" the front end for a fat, distorted sound, then cut some bass at the output to tighten up the sound without losing dirt.

Perfect! This is exactly what I was looking for. A "basic" starting point and understanding why.
I wish I had more time to devote to digesting the technical side of things but life has a funny way of eating up time you try to put aside *Sigh*

And when that happens, some of us (me, actually) has to resort in asking what seems to be ridiculously elementary questions and look sillier (trust me, I am making silly faces as I type type this) asking them

As to you ramblin' on - I don't mind at all.

I appreciate the time you took Travis, to answer this for me

[Chris60601]

Frank_NH wrote

Like everything, experimenting (using a breadboard) can be very instructive.   If you are more into circuit design, I would highly recommend getting a learning to use a circuit simulator like LTSpice.  You can examine so many "what if" scenarios before you go to the breadboard and in turn get a better understanding of what effect different component substitutions make on the circuit.  

As time allows, I really should take this advice seriously since I seem to spend more time on the lappy (with work and all) and I could use the down time for looking into this. It certainly seems like I could eliminate lots of potential breadboard-time this way.

Feels like soooo much to still learn and just feels like sooo little time left to do it. Take it from me; go balls in to whatever you love or do as a hobby. Start out young and early. Put down the smoke and drink a few times and devote it something you love ... Unless of course its smoke and/or drink, lol

Thank you, Frank

[Frank_NH]

The key to learning LTSpice is to start with something small, like a simple transistor booster, and then gradually work your way up to more complicated circuits.  You can look at both the output wave forms (like a virtual o-scope) and the frequency response, which gives you a great understanding of how the circuit will sound.  And then you can change component values as you like until you fine tune the circuit.  Then, go to the breadboard and build it.   That's the most fun of all since you can actually hear your circuit live!  When you've tweaked it further and finalized the schematic, you can then go to vero or PCB layouts.  Lot's of fun and education at the same time!