Adding a tone switch

[frankenbeans]

Hello All,

I am looking to build a red llama clone and I am repurposing an enclosure which has two holes drilled for pots and one for a mini toggle switch.The Red Llama doesn't have a tone switch and I don't want to have a disconnected toggle filling the hole so my question is;

Would an on-off-on SPDT switch with two caps (for instance in the range of 5-47nF) going to ground work as a tone switch? If so, where on the board would I connect it? Would it just be at the output? And if not, what are my options so I have a functional toggle switch on my pedal?

[mauman]

You're close!  To make a lowpass filter (treble reducer), you need Resistance and Capacitance. Resistor goes in series with the signal, capacitor goes from the signal to ground.  If you add a 100 ohm resistor in series between pin 2 of your IC and the 10 uF output cap, that's your resistance.  Then you can add a wire from the point where the 100R connects to the 10 uF cap, to your on/off/on tone switch lug 2.  Lugs 1 and 3 of that switch go to 2 different caps, and the other side of those caps go to ground.  You can then either experiment with various cap values, or use a calculator like this one to predict the cutoff frequency of 100 ohms with various caps.  For example, 100R + 300 nF = 4.8 kHz.  The cutoff frequency is also called the rolloff frequency or the -3 dB point.  https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-low-pass-and-high-pass-filter

[frankenbeans]

Thanks Mauman - what's the reason the resistor has to be between pin 2 and the 10uF cap?

[mauman]

It could go elsewhere, but I like putting it there which will do the EQ after the last gain stage (which comes out of pin 2) but before the cap that isolates the circuit from the outside world (10 uF cap.)  It would also work before or after the first gain stage.