- Minijack connectors originated from 1870s telephone switchboard plugs.
- Audio signals are AC, measured in Vrms; typical full-scale voltage on consumer hardware is ~1.25 Vrms.
- Nominal operating voltage is -10dBV (0.316 Vrms), but standards vary.
- Professional +4dBu standard uses 1.228 Vrms nominal with more headroom.
- Reference 0 dBu = 0.7746 Vrms comes from old telephone 600-ohm matched loads.
- USB dongles like ADA-17 output ~0.973 Vrms due to power constraints.
- MacBooks support multiple voltage ranges (1.25, 3.0, 1.0 Vrms) depending on impedance.
- Volume attenuation is nonlinear: quadratic for ADA-17, cubic for Mac's 3V output.
- Minijack cables lack strict standards, but are used successfully to connect military radios to laptops.