This nifty little device will allow output of up to 24-bit/192kHz S/PDIF from a USB port. The hiFace looks a bit like an oversize USB flash drive with an RCA or BNC connector on the opposite end. Using a USB device allows one to employ a much smaller and easier to cool computer and I ended up with a “nettop” class of machine. This is much like the netbook laptops using an Intel Atom processor and a 2.5-inch hard drive. Passive heat sinks are enough to provide cooling without fans and the small hard drive is very quiet and inaudible from my listening position, avoiding the expense of a solid state drive. Unfortunately most of the USB devices, either DAC or S/PDIF output do not support the highest resolutions available and often use the PCM2702 from Texas Instruments, which is limited to 16-bit/48kHz. There are some very nice USB DACs available from Ayre Acoustics and Wavelength Audio to name a few but for the low budget audiophile like myself they are still a stretch of the wallet.
The M2Tech hiFace operates asynchronously with two high precision clocks covering the multiples of 44.1/88.2/176.4kHz and 48/96/192kHz. These clocks have a claimed precision of 2.5 ppm and very low phase noise. The use of a high performance transmitter allows the output to have extremely low jitter and M2Tech employs a pulse transformer to provide galvanic isolation from the computer. At this time M2Tech offers drivers for both the Macintosh and Windows operating systems. Linux support is forthcoming. Since my day job is working with Windows based machines I don’t have any experience with the Macintosh version and look forward to giving it a go under Linux once the drivers are available.
The hiFace is primarily designed to use kernel streaming under Windows, regardless of version. This ensures low CPU utilization even at high bit depth and sampling rates and allows for a highly optimized driver. M2Tech supplies proprietary
Input for an external clock for those who have a extremely precise and stable clock generator to be used with hiFace Evo. hiFace evo automatically recognizes the presence of the clock on its input and switches on it whenever available.
LOW JITTER, LOW PHASE NOISE, HIGH STABILITY OSCILLATORS Most audio interfaces and USB-provided DACs refer the data stream clock to the same USB interface clock, that often suffers a very heavy jitter (short range oscillator frequency variations). Thanks to two quartz precision oscillators used on M2Tech hiFace, clock source for output data stream features a very low jitter. A more stable clock is recovered by DAC S/PDIF receiver; a low jitter produces a very limited sound image distortion and degradation. Phase noise (main responsible for jitter) is also very low: this guarantees a short and long range clock stability, also reinforced by a board supply voltage regulation (e.g. at environmental temperature stability is 2-5ppm approximately, compared to 50-100ppm performed by oscillators normally used on commercial CD players).
The standard audio drivers available on the market (e.g. Microsoft Windows operating system) dictated constraints can be overcome thanks to hiFace proprietary drivers: they allow for transferring audio data, maintaining the original file quality without any loss of resolution quality; also, sampling frequency constraints are overcome, while Microsoft and ASIO drivers oblige to operate at no more than 96kHz. When hiFace is used together with a player application such as FooBar (available for free on Internet), you can transfer S/PDIF stream music files to a D/A converter at 192kHz/24bits maximum frequency/resolution, avoiding undesired PC or MAC audio mixer data processing during the data transfer from hard disk to interface. Presently, Windows XP, Vista, Windows 7 drivers are available, as well as Mac drivers for 10.4, 10.5 and 10.6.
M2Tech hiFace features a very compact size and can be directly (or using an accessory USB A-A adapter, not supplied with hiFace) connected to a High Speed USB 2.0 port of any computer. A very high electric and mechanical performance RCA gold connector provides an output signal, ready to be connected to a Hi-End system. No external power supply is required, as hiFace draws its power from USB bus itself and regulates it with its internal regulators. hiFace USB interface connected to a last generation mini PC provided with a High Speed USB port makes for a complete music transport system at very low prices (in the range of few hundreds Euros). Such system allows for listening any density and resolution music files, playing own CD’s using a CD ROM drive, obtaining access to more than 10,000 web radio, many of which broadcast their transmissions with CD quality.
Several outputs are available at the same time: coax on RCA, coax on true 75 Ohms BNC, AES/EBU on male XLR, optical on ToslinkTM (ToslinkTM is guaranteed to operate up to 96kHz, though we got operation up to 176.4kHz on certain setups), optical on ST (for high-speed operation up to 192kHz and up to 1.6km or 1 mile), straight I2S for direct connection to DIY DACs on RJ-45 (NOT plug-in compatible with NorthStar products!). All outputs, except straight I2S, are galvanically isolated (coax and AES/EBU via a pulse transformer). AES/EBU output can be set to professional or consumer mode by an internal jumper.