An electronic sound chip stores digitized sounds. A PIC processor controls sound card operation, utilizing a free comparator present in the PIC processor that detects variable DC offsets, and thereby activates at least one “voice” or channel of sound. The system self-calibrates on the initial power on, and the calibration values are measured and stored internally in non-volatile storage for later comparison against the DC offset to frequency thresholds. The system detects loss of power, which mutes the audio during power interruptions for seamless model train direction control.