NuPrime DAC-9X

Hitherto better known in hi‑fi circles, NuPrime make converters of a quality that could appeal to pro audio users.

American company NuPrime are probably better known in the hi‑fi market than in pro‑audio circles, but their lineage dates back to 2005 in the form of a company called NuForce that was founded by Jason Lim, a man whose previous career path involved designing microprocessors and Internet technologies for the likes of Motorola, Sun Microsystems, Oracle and others. Lim served as the CEO of NuForce for eight years, during which time the company became a leading light in Class‑D amplifier technology, amongst other things. In 2014 he founded NuPrime, which acquired the high‑end audio division of NuForce and started creating high‑quality products for the hi‑fi, home‑theatre and gaming markets. In their second year, NuPrime won four Product of the Year awards, and they’ve gathered many more accolades since.

The company currently make seven different D‑A converter (DAC) products, but the NuPrime DAC‑9X has been designed specifically for “studio professionals”, which is why this one has made its way to us at SOS for review. In essence, it’s a reference‑grade DAC with a variety of digital and analogue inputs and outputs, plus a standard quarter‑inch stereo headphone output. So it could conceivably serve in the studio or on location as a straight stereo D‑A converter, a source selector and preamp, and as a headphone amplifier.

Technology

Unusually, NuPrime’s DAC‑9X is built with a dual‑mono signal path, based around a pair of ESS Sabre ES9028Q2M digital‑to‑analogue converter chips. The 9028Q2M is a very high‑performance stereo D‑A converter that uses the manufacturer’s highly‑regarded 32‑bit Hyperstream technology, which is potentially capable of delivering a dynamic range of up to 129dB. It supports PCM sample rates up to 384kHz, as well as the DSD format up to DSD512 (22.6MHz). Although designed as a stereo D‑A converter chip, it can be configured as a mono converter, with the two channels working together in a balanced configuration. This arrangement provides a further 3dB improvement in the noise performance, and is how and presumably why it is being used here — hence there being two of them. The ESS converter includes a variety of onboard DSP functions for different reconstruction filter responses, de‑emphasis filtering, and volume control, but none are available to the end user; all are preset in the DAC‑9X by the manufacturer.

Inside the box, the conversion is based around a pair of ESS Sabre ES9028Q2M chips.

Separately, additional DSP functionality (courtesy of an XMOS processor) recognises and decodes MQA‑formatted audio files (for more on MQA see our SOS August 2016 article: https://sosm.ag/mqa-format), as well as supporting DSD‑encoded audio via either the ASIO 2.1 (over USB) or DoP (DSD Over PCM) formats. Although there is a digital volume control included within the D‑A converter chips, NuPrime have chosen to use a separate, digitally controlled, 99‑step analogue switched resistor network for the DAC‑9X, to avoid noise and distortion artefacts.

Internal construction is to a high standard, with the toroidal transformer and power regulators towards the front of the unit, and all the converter, analogue output and control circuitry on a large circuit board at the rear of the unit, constructed using SMD components.