There is a familiar formula for the attenuation of a voltage divider formed by two resistors: A = R2/(R1+R2). Not so familiar are the formulas for determining the value of R1 or R2 when a specific amount of attenuation is desired. Too often I find myself having to apply some algebra to invert the formula. Occasionally I get it right the first time without mixing up R1 and R2. To eliminate this minor irritation, here is a calculator that determines the unknown resistor value.
1Richard Kuehnel, Vacuum-Tube Circuit Design: Guitar Amplifier Preamps, 2nd Ed., (Seattle: Pentode Press, 2009).
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