Effects input Capacitor Selection

[SlashLP97]

I'm new to building effects pedals and I was just wondering if there was a reason for all the .1uF and .01uF capacitors in series with the input of most effects pedals being the values they are.  I know you need these very often to shift your signal up to center around 4.5V instead of around 0, but why cut out so many bass frequencies?  Is there some reason for having a gain <<1 on frequencies less than a few kHz?

[MohiZ]

Wait... for a .01uF cap and 1M pull-down resistor the bass roll-off frequency would be 15Hz?

[SlashLP97]

Ah, I see.  In my simulation I just used the initial resistor value of 1k.  Thanks!

[MohiZ]

If you're talking about the cap in the input of the whole effect, usually a resistor of at least 470k to ground follows. Between different amplification stages there might be bass attenuation, especially in distortion effects, since too much bass makes the distortion sound flabby.