I bought this I²S transport specifically as a project, but it's a finished item, too, depending on what you want to do with it. This V2 model incorporates a Raspberry Pi 3, an Allo Kali reclocker and an HDMI send board. What it does is run a software build, like Volumio, handling all your files and streaming requirements in a straightforward GUI environment, and streams the music out to an I2S DAC. The small enclosure is professionally finished and attractive, far better than many of the rather amateur looking Pi enclosures (including Allo's own). The whole thing costs €269 which is a fair price to pay for a properly finished product complete with SMPS power supply.

I²S (Inter-IC Sound) is not that new a data format, being invented in the early days of CD, but I²S over HDMI is much more recent and an invention of PS Audio in order to send I²S externally to a DAC using inexpensive HDMI cables (standard I²S can only cope with a connection length of a few cm). There is a rival system called I²S over ethernet using network cable as the transmission medium. To further complicate things, there are two connection standards for I²S over HDMI (IIS-H), the original PS Audio scheme and one that Gustard, LKS and other mostly Chinese DAC vendors use. The world did not need two incompatible IIS-H systems!

The Audiophonics comes as standard with an HDMI board which sends in PS Audio format and can be used out of the box with a PS Audio DAC or one following their standard. As supplied, it is not compatible with the Gustard/LKS standard as it requires a different HDMI board.

Not one to be dissuaded at the first hurdle, I set about buying an HDMI sender board in the correct format (mine supports both standards) and sporting the same mounting holes as the original. One order on eBay later and the correct board was secured for just $30. Hooking it in was a matter of connecting short cables to the same pins on the Kali as previously used, namely MCLK, BCLK, LRCLK, Data, +5V and GND. Did I mention this was a project?



The Kali is an excellent reclocker, sporting two crystals for the 44.1kHz and 48kHz sampling rate range and therefore being of much higher quality than the Pi's single crystal. It supports jitter-free reclocking at 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, 192kHz, 352.8kHz and 384kHz with 16-bit, 24-bit or 32-bit data. Output jitter is less than 4ps. There are a whole raft of onboard LEDs indicating power, buffer full, signal lock, sample rate and selected crystal - very helpful indeed for debugging and getting it all going. It's a shame that the light show is completely hidden when the case is closed.

The Audiophonics accepts 5V DC power via a rear panel 5.5mm DC socket and comes complete with the aforementioned SMPS plug unit. This is routed to the Kali which then cleans the DC for its own processing and feeds a raw 5V feed to the Pi. There is a front panel switch and blue LED for controlling power.

I took one look at this and decided I wanted dual separate 5V feeds to keep the 'dirty' Pi power well away from the sensitive 'clean' Kali power. Easily accomplished: I removed the short link cable from Kali to Pi and the superfluous standard HDMI socket (the one for connection to a TV) from the rear panel and used a microUSB power cable into the Pi to feed it with separate 5V. Meanwhile, the Kali remains fed from the rear panel socket. Nice.



There are many different software builds for the Pi and as long as they support the Allo Kali they can be used. My personal choice is Volumio and I had no difficulty burning a microSD card and getting the whole thing fired up. The correct driver setting in Volumio for the Kali is Pi-DAC but Allo can give support on the correct settings for different software builds.

For the network feed into the Pi I strongly advise ethernet cable as sounding the best, especially if it's a straight run from your router. Failing that, you can configure the Pi for wi-fi, too.

If it all works correctly, your DAC will spring into life displaying Lock and IIS-H (or similar) when the startup tune is played. Once everything has settled down, you will have a chance to listen to a streamer/DAC combination connected by a data link which preserves separate clock and data, giving your DAC a chance to perform at its best.

There's more, of course. A high quality dual linear PSU, or even better a supercap PSU like the Coherent QP-1 that I use, really takes the streamer to its next level. The HDMI cable quality matters, too. I'm using an Audioquest Cinnamon silver plated HDMI cable, the best of a handful of cables I've tried.

Looked at as a project or as a complete ready to run streamer, the Audiophonics is a nicely enclosed unit using well regarded and well supported components that does its job well at a very reasonable price. It's capable of an almighty high end performance limited only by your choice of DAC and power supply.