better math?

spice/rvals-theory2.md

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+# Resistor Values and Combinations
+
+...with reducing resistor count as a priority.
+
+This time not while half-asleep.
+
+## 90Hz-110Hz
+
+### low-pass
+$(120 \parallel 47) + 3.3 = 37.072 \Omega$
+
+### high-pass
+$(68 \parallel 47) + (470 \parallel 2.2) = 28.245 \Omega$
+
+## 290Hz-310Hz
+
+### low-pass
+$22 + 22 + 10 + 1 = 55 \Omega$
+
+### high-pass
+$47 \Omega$ resistors are already available.
+
+## 950Hz-1050Hz
+
+### low-pass
+$((68 \parallel 68) \parallel (68 \ parallel 68)) = 17 \Omega$
+
+### high-pass
+$(10 \parallel 10) + 10 = 15 \Omega$
+
+## 3.2kHz - 3.4kHz
+
+## low-pass
+$47 + 1 + 1 = 49 \Omega$
+
+## high-pass
+$22 + 22 + 1 + 1 = 46 \Omega$
+
+## 9khz - 11khz
+
+## low-pass
+$(10 \parallel 10) + (47 \parallel 3.3) + 10 = 18.083 \Omega$
+
+## high-pass
+$(22 \parallel 22) + 1 + 1 + 1 = 14 \Omega$ (better tolerance)
+
+Alternative: $10 + 1 + 1 + 1 + 1 = 14 \Omega$ (worse tolerance)
+