better math?

spice/rvals-theory1.md

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+# Resistor Values and Combinations
+
+The schematic calls for resistor values that are not available to us without some light sorcery. This is an attempt.
+
+Every resistor from the pack is rated for 0.25W and has a tolerance of $\pm5%$. Want to figure out how that could affect my calculations? Me neither.
+
+## 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
+$(220 \parallel 68) + 2.2 + 1 = 55.144 \Omega$
+
+### high-pass
+Luckily, we already have 47 $\Omega$ resistors.
+
+## 950Hz-1050Hz
+
+### low-pass
+$(22 \parallel 47) + 2.2 = 17.186 \Omega$
+...or alternatively:
+$(10 \parallel 10) + 10 + 1 + 1 = 17 \Omega$
+
+### high-pass
+$(10 \parallel 10) + 10 = 15 \Omega$
+
+## 3.2kHz - 3.4kHz
+
+## low-pass
+$47 + 1 + 1 = 49 \Omega$
+
+## high-pass
+$22 + 22 + 1 + 1 = 46 \Omega$
+
+...no one ever said we had to be clever.
+
+## 9khz - 11khz
+
+## low-pass
+$(10 \parallel 10) + (68 \parallel 3.3) + 10 = 18.147 \Omega$
+
+## high-pass
+$(22 \parallel 22) + 1 + 1 + 1 = 14 \Omega$
+
+---
+
+# Bonus: some fun(?) and useful(?) resistor values
+
+$(10 \parallel 10) = 5 \Omega$
+
+$(220 \parallel 22) = 20 \Omega$
+
+$(22 \parallel 22) = 11 \Omega$
+
+$(100 \parallel 150) = 60 \Omega$