Guitar Pedal Circuit Calculators & Tools If you would like to suggest a calculator or tool, make a request using the Calculator Request Form! Voltage Divider Calculator Series & Parallel Resistance Calculator Series & Parallel Capacitance Calculator Low Pass Sallen-Key Filter Calculator Relaxation Oscillator Calculator Fuzz Face Germanium Transistor hFE Tool Schmitt Trigger Oscillator Calculator Indicator LED Current Limiting Resistor Calculator Common-Emitter Amplifier Calculator PT2399 Calculator RC Low-Pass Filter Interactive Tool RC High-Pass Filter Interactive Tool RC Low-Pass Shelving Filter Tool LM317 Voltage Regulator Calculator RC Filter Cut-Off Frequency Calculator Capacitive Reactance Calculator