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Me Here 5a75dbbbdc PM_K-1 hardware: Stage 4 -- balanced output driver (completes the audio chain) 
THAT1646 balanced driver (pinout verified, THAT doc 600078 rev07) closes the chain:
MIX_OUT -> 25-turn level-cal trim -> THAT1646 (+6dB, sense tied local) -> 47ohm
build-out -> fail-safe mute relay K2 -> balanced AOUT_HOT/COLD on the interconnect;
ground-lift relay K3 (de-energized=bonded, soft-lift 100R||10nF) -> CHASSIS.

- Phase: Stage 3 inversion corrected via HOT<-OUT-, COLD<-OUT+.
- Level cal trim ahead of the driver (its +6dB gain is fixed).
- K2 fail-safe: de-energized shorts both legs to GND after the build-out (driver
  current-limited). K3 ground-lift in series with a face panel switch.
- stage4_driver.cir: differential flat +4.76dB (1k=20k), legs antiphase (0 vs pi rad),
  build-out+cable rolloff above audio. ERC 0 errors; netlist 0 errors.

AUDIO CHAIN COMPLETE: stages 1, 1b, 2, 3, 4 all captured + simulated + ERC-clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-05-30 20:27:04 -05:00
..
circuits PM_K-1 hardware: Stage 4 -- balanced output driver (completes the audio chain) 2026-05-30 20:27:04 -05:00
sim PM_K-1 hardware: Stage 4 -- balanced output driver (completes the audio chain) 2026-05-30 20:27:04 -05:00
Containerfile PM_K-1 hardware: Stage 1 input receiver as SKiDL (code-defined schematic) 2026-05-30 19:43:07 -05:00
README.md PM_K-1 hardware: reproducible EDA container (KiCad 9 + ngspice) 2026-05-30 19:17:54 -05:00
run.sh PM_K-1 hardware: reproducible EDA container (KiCad 9 + ngspice) 2026-05-30 19:17:54 -05:00

README.md

PM_K-1 EDA environment

A reproducible container with the tools to design, check, and simulate the core board — so the work doesn't depend on whatever happens to be installed on a given machine, now or in 50 years.

What's inside

  • KiCad 9 — schematic capture + PCB layout, and a CLI (kicad-cli) that can run ERC (Electrical Rules Check) and DRC, and export netlists/PDF/Gerbers.
  • ngspice — SPICE simulator for validating the analog audio circuits before we commit copper (op-amp stages, filters, input loading, etc.).
  • python3 — scripting, BOM munging, optional code-defined-schematic helpers.

Why a container?

The system KiCad here is 7.0, whose CLI can't run ERC (that arrived in KiCad 8). Rather than fight the host, we pin a known toolchain. Anyone — including future-you — rebuilds the exact environment with one command.

Use it

cd hardware/eda
./run.sh                                   # interactive shell, lands in hardware/kicad/
./run.sh kicad-cli version                 # confirm KiCad 9
./run.sh kicad-cli sch erc pm_k1_core.kicad_sch   # run ERC on the schematic
./run.sh ngspice -b ../eda/sim/input_loading.cir  # run a simulation (cwd is kicad/)

run.sh builds the image on first use, then mounts the whole repo at /work (so KiCad sees hardware/). Use RUNTIME=docker ./run.sh … to use Docker instead of Podman.

Layout

eda/
  Containerfile      # the pinned toolchain (KiCad 9 + ngspice + python)
  run.sh             # build-if-needed + run with the repo mounted
  sim/               # ngspice decks (SPICE simulations of the analog circuits)