Many of you know the backstory behind iFi Audio. In essence, the firm is a spin-off from the well-regarded British high‑end audio company Abbingdon Music Research (AMR) and iFi’s mission is to make AMR-like technology and sound quality accessible to music lovers through several series of compact and affordable components. As you might expect, there are distinct echelons within the iFi range, starting—in ascending order of size, price, and performance—with the Nano range, followed by the newly launched “X” range, then the Micro range, and, at the very top of the pyramid, the Pro-series range. iFi’s present Pro-series range comprises three models: the Pro iCAN headphone amp/preamp, the Pro iESL electrostatic headphone adaptor module, and the recently released Pro iDSD DAC/headphone amp/preamp/streamer, which is the subject of this review.
Stated simply, the Pro iDSD is far and away the most sophisticated and technically advanced DAC that iFi Audio has ever offered and its features set is so forward looking that it would not seem at all out of place in a DAC selling for, say, ten or more times the Pro iDSD’s price. Technically speaking, there is so much going on inside the Pro iDSD that it’s hard to know where to start with a description, but let me begin with some of the core features of the DAC and then work outward from there.
At the heart of the Pro iDSD is a quad interleaved set of Bit-Perfect DSD and DXD DACs from Burr-Brown for a configuration that, says iFi, “means that up to eight pairs of differential signals can be used and mixed – four pairs of signals per channel”. There are five digital inputs: USB, AES3, S/PDIF (coaxial and optical combo), BNC multifunction (S/PDIF or Sync input), and a WiFi/Network/Mass Storage interface. All inputs are galvanically isolated to minimise noise.
Audio data from all inputs is routed to a memory buffer, where it is de-jittered and then reclocked via a femto-grade Global Master Timing clock whose design is drawn from the clock used in the big AMR DP-777 Digital Processor. Decoding processes for all digital audio file formats is handled by an XMOS X-Core 200 processor, while digital filtering and DSD Remastering (more on this in a moment) functions are implemented through a powerful Crysopeia FPGA device.
By default, PCM files are played in Bit-Perfect (BP) mode, but Bit-Perfect+ (BP+) mode can also be used: neither the BP nor BP+ modes upsample PCM data. However, when users choose one of the Pro iDSD’s three other available PCM filter options—including Gibbs Transient Optimised (GTO), Apodising (AP), and Transient Aligned (TA) filters—PCM files are automatically upsampled to 705.6kHz or 768kHz rates (that is, 16x PCM) depending on the sampling rate of the original file. One further option is to take these PCM files, whether bit-perfect or upsampled and filtered, and to run them through the Pro iDSD’s sophisticated ‘DSD Remastering’ engine, which can output either DSD512 or “studio-grade” DSD1024 files.