Released at the end of the first decade of the new millennium, eyebrows were raised when Naim Audio gave us its first ever standalone digital-to-analogue converter. The company said it wasn’t worth doing one until it could make something that was technically innovative – and so it proved. The £1,995 Naim DAC was designed specifically to deal with jitter issues and very largely done in-house. This showed a certain seriousness on Naim’s part at a time when many rivals were repackaging generic chipsets. Designed by Naim’s Steve Sells and Hjalmar Nilsson – whose other notable work surfaced in the DSP used in the Naim for Bentley project – it sported a (then) very fast and powerful SHARC digital signal processing ‘brain’ running Naim authored code. This gave the freedom to wrest full control of the digital domain, rather than leaving it in the hands of third party manufacturers.
The traditional problem with a separate transport and DAC has always been the disconnect between the two; the DAC has to recover the clock from the S/PDIF signal, which itself is very prone to timing errors. In the Naim DAC, the data wasn’t recovered directly from the S/PDIF signal, but read in and stored in solid-state memory, then clocked back out to the DAC chips using a fixed-frequency local master clock. The DAC can vary its own clock speed according to the rate of flow of the data coming into it. The SHARC DSP chip assesses the rate at which the data is coming in then nominates one of ten precisely set master clocks to send it through the DAC.
In this way, Naim says, the data entering the DAC chips is completely isolated from the incoming jitter. Only in rare cases will none of the Naim DAC’s selectable master clocks be closely enough matched to the incoming data rate, in which case an asynchronous sample rate converter (ASRC) is used. Integer oversampling is used to as high a frequency as is possible given the source; for example, 44.1kHz CD is oversampled 16 times. The DAC chips themselves are two mono, true multi-bit Burr-Brown PCM1704Ks, as used in all Naim high-end CD players including the CD555, and are capable of running with an input data clock of 25MHz, which allows sample rates of up to 768kHz.
As you’d expect, meticulous attention is paid to circuitboard layout from an electrical point of view. Star earthing is used extensively, while the 210 VA toroidal transformer feeds 26 regulated low impedance supplies. When the external PSU upgrade option is used (XPS or 555 PS) with the Naim DAC, power supply separation is increased by the use of a dedicated supply for the master clock circuits. It also provides a bigger toroidal transformer and bigger reservoir capacitors, and the DSP remains powered from the Naim DAC transformer to give even more separation from the analogue section.
The circuitry has also been designed to reduce mechanical noise (i.e. vibration). The starting point is a rigid aluminium chassis with 3mm-thick panels, with the fibreglass printed circuit boards screwed to the chassis only at certain points, with other parts of the PCB resting on pillars to reduce energy transfer. To isolate vibrations associated with reservoir capacitor charging, the power supply PCB is separate from the main PCB. Analogue stage filter capacitors are mounted to minimise microphony.
The Naim DAC wasn’t conventional on the outside either, coming with a host of connectivity options, most interesting of which was (at the time) the USB facility. Notably, it was the world’s first Apple-authenticated high end DAC, offering full digital play out of iPods via their docking connector feeding the Naim’s USB input. There are even ‘transport’ controls for the iPod, front mounted on the DAC, and it also works via the Apple Remote. Additionally, the DAC will also play out USB memory files, with audio of up to 768kHz sample rates, via the two type A USB inputs (one on the front panel, the other at the rear). It will not play USB music direct from computers however; Naim said this was too noisy for serious sound, and suggest using an optical digital feed from a USB soundcard. Also fitted are eight S/PDIF inputs (two BNC, two RCA and four EIAJ optical.
I described it at the time as a very modern, contemporary sounding device, devoid of any romance, mystery or euphony. It has a tight, firm and propulsive sound that’s tonally dry, with dark silences and and a light, shimmering upper midband when called for. The midband has an icy clarity; everything is picked out in a cool, unromantic way; this doesn’t mean it’s cold or uninvolving, it’s just that the Naim doesn’t feel the need to charm or beguile the listener. It’s brutally matter of fact, in the best possible way.
Although very detailed, it doesn’t sound deconstructive; it does very hi-fi things, but not it an obviously hi-fi way. Vocals are handled extremely well, especially their rhythmic phrasing and dynamic accenting. Music is rendered with great clarity, yet the Naim carries real emotional force. Bass notes stop and start on a sixpence, midband is crisp and open and treble highly atmospheric. Clarity, insight, depth, space and natural musicality are all far better than equivalently priced DACs of its day. Nowadays, you can arguably do better at its £2,749 price, but it’s still a great product and a secondhand bargain for under a thousand pounds…