Nad is a manufacturer of HiFi components established in 1972. Their aim, as stated on the web site www.nadelectronics.com is for performance, value and simplicity. Indeed, their specialism seems to be in producing components that intentionally do not include a large amount of gimmicks, or too many equaliser controls which spoil the pure signal from the input to the amplifier. For example their CD player the C520, awarded 5 stars by What HiFI? lacks such a common feature as an optical output – presumably a result of the pursuit of quality over features.

The logo of the Nad mp3 player looks vaguely similar, so I think perhaps it was based on the HiFi manufacturer.