How Capacitors influence harmonics octaves

[tenser75]

So... i built a B2 ig muff clones and i tested two config

- one with all 470nF grey boxed caps (replacing all the 680nF/470nF/1uF) and 470pF (all ceramics)
- a second one with 100nF (replacing all above, film dipped caps) and 560pF (all ceramics)

the first one with bigger caps has a interesting low harmonic, a low octave, i'm not sure how describe it...almost synth-y resonance
whereas the second is smoother (probably the 560pf cuts high frequencies more)

i noticed it playing them with a Ditto looper and a switcher, so i could go back and forth quickly

so, i know caps capacity influences frequencies, but I'm curious to know more about it... I thought they were just influencing the amount of bass/highs...not really lower octaves..etc..

if you have experiences or examples like mine to share...

[R.G.]

Welcome to the addiction.

Capacitors by themselves do ... nothing ... to frequencies. They can only have an effect on frequencies when used combined with resistors, inductors, other parts.

Capacitors work by "impeding" electrical flow differently at different frequencies. An ideal capacitor is an insulator at DC. But it "impedes" electrical flow less as the frequency of the electrical voltage across it increases. That is, its impedance drops linearly with frequency.

A capacitor that has an impedance of, say, 100 ohms at 500Hz will have an impedance of 50 ohms at 1000Hz, and 25 ohms at 2000Hz. Or  1000 ohms at 50Hz. None of that changes the amount of electrical signal coming through until you combine it with other parts.

A capacitor combined with a resistor can be a low pass filter or a high pass filter, depending on how it's with the resistor, and whether you're looking for signal voltage coming through or signal current coming through.

So - again, welcome to the addiction, and get started reading. You have a ways to go, but it ought to be a fun ride for you.

[blackieNYC]

I've accidentally made a subharmonics pedal - a heavily distorted thingy that gives me odd bursts of subharmonics perhaps like you describe. I suppose if I hit it with more lows from the guitar (larger series caps, moving the corner freq of the effective rf filter downward) the subharmonics are more extreme, and less so with smaller caps.
Not sure why it happens. Octave down, even some 4s& 5s.

[anotherjim]

If you made square waves, one thing that high pass filtering can never do is remove the fundamental. It's there in the period of the spikey waveform you get out. Nature tends to draw a sine wave - in the air if necessary - out of it.

Now to get a sub octave (are you sure you aren't hearing the pure fundamental?), I think the spike wave needs asymmetric clipping and, just my theory so far, this adds to the wave some stuff that's only occurring every other half cycle, which is a divide by 2; and nature makes a sub octave sine out it. I think there are enough stages in a BMP to do that, especially since the BJT's are unlikely to be biased perfectly to clip symmetrically.