Audio chain, stage 1 (balanced input receiver + protection) validated in ngspice:
- stage1_cmrr.cir: CMRR vs resistor matching -> 1% = 46dB, 0.1% = 66dB, perfect
= amp-limited; justifies the laser-trimmed THAT1240 over discrete resistors.
- stage1_phantom.cir: +48V phantom step -> clamped to ~16V blip, steady-state
~0.12V; the DC-block cap + clamp + series R make a miswire a non-event.
Container: add kicad-symbols + kicad-footprints (for symbol placement) and skidl.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
