Adding passive bass control knob to OD

[REE]

Hi guys,
I'm just wondering how I should add a bass control knob on a 3 knob overdrive (like the MXR Badass Custom OD).
Thanks!

[Mark Hammer]

G&L and Reverend guitars often incorporate such a control, which they label "Contour".  Joe Gagan also came up with a similar control for the input of fuzzes.

It works like this (at least in this guitar circuit)  The signal has two parallel paths it can pass through: the .0015uf capacitor, and the leg of the pot in parallel with it.  When the pot resistance is high, what can squeeze through the cap predominates.  When the pot resistance is lowered, the resulting signal becomes more full bandwidth (i.e., also includes lower frequencies).


The Univox Square Wave also uses a similar bass-reduction Tone control.  Just note that, if you insert such a bass control near the output of your pedal, you will need to make sure there is some form of DC-blocking for the output.  In the Square wave, the .001uf cap will certainly do that, but DC can "sneak around" that cap.  Fortunately, the 4.7uf cap a little earlier in the circuit, keeps DC out of the output, regardless of where that Tone control is set.

[antonis]

How many pots got damaged by following body solder instructions..??

[REE]

@Mark Hammer
Thanks mate!
Just wanna double check, is this how you draw it on a schematic?

[Mark Hammer]

Yes.