Low pass filter added to a pedal circuit?

[Xander8280]

I made a fuzz pedal which sounds a ton better with the tone rolled off. For easier application I want to add a low pass filter at the beginning of the circuit that will sound like a tone knob on a guitar...
I used a resister and cap and I got a big volume drop and no distortion. I know some RC math and the low pass and high pass set ups with resisters and capacitors. The tone control on a guitar doesn't really look like a low pass. Can anybody shed some light?
Thanks for reading, I'm desperate

[Mark Hammer]

1) The guitar tone control IS a low pass, just a different configuration.

2) Your signal amplitude is the sum total of the entire spectrum.  If you cut out a big chunk of the spectrum with serious lowpass, you are also lowering the signal amplitude reaching the clipping stage.  There may well be enough gain in that stage (or stages) to produce clipping, but not quite enough to fully compensate for the cut in input signal.

3) Apparent loudness will be a function of the top end.  Clipping stages add harmonics of what they are fed.  If the spectral content of the input signal is VERY dull, then the rssult, post-clipping, may seem lower in level than if the clipping stage is producing harmonics of midrange content.

[ashcat_lt]

The tone control on a guitar is not a simple RC filter.   It's actually a fairly complex RLC low-pass.  The fun part is that the series R that we are used to seeing in basic examples is hidden with the L inside the pickup.  The tone cap is parallel to another cap which hides inside the cable.  The pot is not a component which we normally see in the simplified examples.  It does two things:  1)  at high resistances it isolates the tone cap so that the filter is dominated by the L of the pickup and the C of the cable; b) parallels the load resistance, which is never shown in those simplified examples, but has a dramatic impact on the action of the filter.


(There's also a cap hiding inside the pickup, but its generally small enough compared to the other players that we can ignore it)

[Kesh]

Pedal's schematic and your RC values may help.