I just saw a digital amplifier at the store but it only had analog inputs on it how can they call it digital?

There are several companies manufacturing amplifiers or products with amplifiers in them that may be fooling the public by calling them digital amplifiers. It may not be totally their fault. One manufacturer of supposedly "digital amplifier" chips actually sells hybrid digital amplifiers that only have analog inputs and have Analog to Digital Converters built in so they produce inherently NON Pure Digital audio. Yet they are marketed as "Digital". This is confusing for consumers. Beware of amplifiers calling themselves "digital" that have only analog audio input facilities and no digital inputs at all.