The Eurorack CV Voltage Divider & Attenuator Sizer determines standard E24 resistor pairs to step down high modular synthesizer control voltages into safe ranges for microcontrollers and analog-to-digital converters (ADCs).

### Electrical & Musical Formulas Eurorack modular control voltages span 0 to 10 V (or -5 to +5 V bipolar), exceeding the input tolerance of modern 3.3 V and 5.0 V microcontrollers: - **Voltage Divider Attenuation**: $$V_{\text{out}} = V_{\text{in}} \times \left( \frac{R_2}{R_1 + R_2} \right)$$ - **Decibel Attenuation**: $$\text{Attenuation (dB)} = 20 \times \log_{10}\left( \frac{V_{\text{out}}}{V_{\text{in}}} \right)$$ - **Standard E24 Resistor Matching**: The calculator iterates across standard 5% and 1% E24 resistor values (1.0 k\Omega\ to 100 k\Omega\) to identify the resistor pair that minimizes voltage error against target $V_{\text{out}}$. - **1V/Octave Musical Quantization**: Under the standard 1V/Octave synthesizer specification, 1.000 V corresponds to 12 semitones ($83.33\text{ mV/semitone}$): $$f = 440 \times 2^{(\text{MIDI} - 69)/12}$$ where pitch is synthesized in real time via the browser Web Audio API oscillator.

### Worked Numeric Example Stepping down a 10.0 V modular envelope signal to a 3.30 V microcontroller ADC input: - **Optimal E24 Resistor Pair**: $R_1 = 20\text{ k}\Omega$, $R_2 = 10\text{ k}\Omega$ - **Calculated Voltage Output**: $10.0 \times [10 / (20 + 10)] = 3.333\text{ V}$ (voltage error of only $0.033\text{ V}$) - **Signal Attenuation**: $20 \times \log_{10}(3.333 / 10.0) = -9.54\text{ dB}$ - **Total Divider Impedance**: $20\text{ k}\Omega + 10\text{ k}\Omega = 30\text{ k}\Omega$ - **Pitch Audition**: Entering note C3 produces a $3.00\text{ V}$ CV level and a $130.81\text{ Hz}$ tone.

### Honest Processing & Audio Note Resistor optimization math and Web Audio synthesizer tone generation operate entirely inside your client browser. No circuit schematics, musical notes, or hardware configurations are uploaded to any remote server.