Quick answers for pedal builders

What is Ohm’s law?

Ohm’s law says current equals voltage divided by resistance. More voltage pushes more current through a resistor, and more resistance lets less through. With an LED in the loop, the LED takes its own fixed share of the voltage first, about 2 V for red and about 3.2 V for blue or white, and the resistor sets the current from what is left. That is how you pick the resistor for a pedal’s status LED.

What is an RC filter?

An RC filter is the simplest frequency filter in electronics: one resistor and one capacitor. Arranged one way it is a high-pass filter that removes bass; flipped, it is a low-pass filter that removes treble. Its cutoff frequency is fc = 1/(2πRC), and nearly every coupling cap and tone cap in a guitar pedal is really an RC filter in disguise.

What is a gyrator?

A gyrator is an op-amp circuit that simulates an inductor using a resistor and capacitor. Paired with another cap it forms a bandpass EQ section, which is how graphic EQ pedals and amp mid controls get inductor-style band shaping without the cost, size, and hum pickup of a real inductor.

What is a mid scoop tone control?

A mid scoop is a tone control that cuts a band in the midrange while leaving bass and treble close to full level, the shape behind many "smiley face" amp settings and heavy rhythm tones. Both scoop calculators here are passive, variable-depth versions built two different ways, so you can compare how the same sound is reached with different circuits.

Why do the calculators show a nearest-E12 build?

Real resistors and capacitors come in standard E12 values, so the exact number a formula asks for usually does not exist as a part you can buy. The tone and filter calculators plot your exact values as a solid curve and the nearest-E12 build as a dashed curve, which shows what off-the-shelf components will actually do to the response before you order or solder anything.