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The Naim DAC basically feeds on S/PDIF signals (Sony/Philips Digital Interface) to interact with typical CD players and transports. This serial data transmission protocol bundles r/l-channel data and word clock into a single stream carried over a single cable. Unlike asynchronous USB, this slaves the DAC (receiver) to the transport (sender). As a known issue with this format, source jitter is thus inherited or transferred.

Naim solves this in a way I’ve not come across elsewhere. Audio data extracted from the bit stream enters a buffer. The speed whereby this data exits the buffer for subsequent D/A processing is determined by one of 10 ultra-accurate fixed frequency oscillators. To match the speed of entering and exiting data, the DAC constantly tracks the former by switching in the oscillator which most closely matches it (or adds an asynchronous sample rate converter should none of the 10 fixed-frequency oscillators match). This converts S/PDIF into an asynchronous protocol that is properly de-slaved from the sender and its inherent jitter.

Post buffer Naim relies on proprietary software for their digital filter, then a Burr Brown PCM1704K chip per channel just as their flagship CD555 player does. I/V conversion is discrete and borrowed from the output stages of Naim’s preamps. There are four twinned inputs, i.e. each is both coaxial (2 x RCA/BNC each) and Toslink. Control is via panel switches or remote. As with the firm’s preamps, volume control is also possible via Apple remote. Potential mates aren’t just CD players or transports but also satellite receivers and game consoles.

Two more digital inputs, one front one back, are USB. These accept USB sticks or iPods/iPhones but not computers or external drives as are reserved for Naim’s NDX. Acceptable USB data formats are WAV or FLAC. The rear panel also sports the so-called Link Plug, a multi-pin socket. In hallowed Naim tradition, removing it allows adding the €4.178 external XPS power supply or the €7.498 555PS either of which obviously push the DAC into far pricier strata.