Designing an external digital to analogue converter capable of offering the exceptional musical performance obligatory for a Naim product brings numerous technical challenges. In particular, the S/PDIF interface protocol for digital interconnection has significant jitter and noise problems.
Original solutions to these problems had to be conceived and developed. The Naim DAC has more in common with Naim CD players than with conventional external digital to analogue converters. It overcomes the jitter issues of S/PDIF by reading the data into a "rotating" data RAM buffer independently of its timing signal and reading it out again clocked by one of ten extremely low noise, fixed frequency crystal sine-wave oscillators.
In terms of system topology, the DAC's rotating memory is analogous to a rotating CD feeding raw data to be reclocked. The rate at which the memory fills and empties is controlled by the DAC automatically selecting the oscillator that matches the average incoming clock frequency. The data entering the downstream digital filtering and DAC chips is then completely isolated from the incoming S/PDIF jitter. Along with being a source of jitter, S/PDIF is a potential source of RF noise. The Naim DAC suppresses S/PDIF noise through electrical isolation of its DSP front end from the digital to analogue converter and analogue circuits. Each element is also run from separate power supplies.
The Naim DAC's digital filtering is handled by a powerful SHARC DSP chip running unique Naim authored code to create an ultra high precision 40-bit floating point filter. The filter over-samples by 16 times on 44.1kHz data and provides stop-band attenuation of 180dB on all data. Following the digital filter are the two mono Burr-Brown digital to analogue converter chips, as used in the CD555 CD player. Finally the Naim DAC features a very high performance, low noise, and low distortion fully discrete analogue output stage.
Ground breaking technology and digital audio engineering, however, are purely academic. Listening to the Naim DAC is something else entirely. Startling in its clarity, arresting in its detail, beguiling in its warmth and inspiring in its rhythm, the Naim DAC seduces from the first note.