Minimizes the initial inrush current when flipping the power switch, preventing household or venue circuit breakers from tripping. 5. Troubleshooting Common Circuit Failures
| Test point | Expected (AC mains version) | Car version (SMPS) | |--------------------------------|-----------------------------|--------------------| | Main rails (after rectifier) | ±45V to ±70V | ±35V to ±55V | | Op-amp supply pins (e.g., NE5532 pin 4 & 8) | -15V / +15V | -15V / +15V | | Output transistor bias (Vbe) | 0.5–0.6V | same | | Speaker terminal DC offset | < ±50mV | < ±50mV | nx audio rx 4000 circuit diagram