Disclosed are multi-channel PWM (Pulse Width Modulation) apparatuses and methods for modulating PCM-based multi-channel audio signals read from an optical medium into PWM-based multi-channel audio signals. A multi-channel PWM apparatus and method can reduce noise from amplifying PCM-based audio signals...http://www.google.com/patents/US20040028243?utm_source=gb-gplus-sharePatent US20040028243 - Multi-channel pulse width modulation apparatus
