OK, I've gotten my "production" parts assembled in the final XO design.

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This thing sounds great! I did an A/B compare today with the new passive XO on the right channel and the active XO on the left channel. Surprisingly, on the best mono recording I have (Nat King Cole After Midnight), the passive actually sounds just a tad bit better than the active. Woot. I consider that to be a smashing sonic success. The big 14 gauge perfect lay inductors in the HF section sound clearly better than the prototype inductors, and I replaced the 12 ohm resistor in the RLC notch filter with a pot so I can adjust the attenuation.