Exclusive: Stack Audio Link USB streaming bridge

USB interfaces, clocks, and soundcards
Stack Audio Link
Exclusive: Stack Audio Link USB streaming bridge

Stack Audio is a small British company that does things to sources! It makes a series of clever upgrades for the ever-popular Linn LP12, but recently it turned to the digital side with the Link. The Link is an affordable bare-bones USB music streamer and network bridge for the home, and its genius lies with its simplicity.

In most music streamers, you end up with a multiplicity of inputs and outputs, allowing the listener to connect via S/PDIF, Toslink, AES/EBU, or – for those with built-in DACs – single-ended or balanced line outputs. The Link does none of that; it just outputs to USB, thinking that some of the best recent DAC designs all support USB. This not only saves on circuit board and casework real-estate, but also makes for a lot simpler design; that helps keep costs low, but it also makes it fast and reliable.

Similarly, a lot of companies go deep down the app rabbit hole, while Link just goes open source. That means you might not get the custom interface that people expect of the big guns, but you also don’t have to wait for a month for the app designer to accommodate a new operating system update on your tablet. However, Stack has a custom-made open-source Volumio app for both iOS and Android. Apps like Bubble UPnP or Kinsky are fine and stable alternatives anyway. Along with UPnP, Link is both OpenHome compliant and a Roon endpoint, so it is not some digital backwater.

First, it’s phenomenally well made, and not just ‘well made for the price’. The milled-from-solid aluminium clamshell case (looking and sized roughly like a Mac Mini which had a bit shaved from its side) is an unexpected bonus and helps keep the circuit within away from too much resonance and vibration. This anti-interference goal is clearly a key part of Stack Audio’s DNA, as a big part of the design is what the company calls ‘signal detox’, which includes a lot of reclocking and otherwise jitter-busting the USB signal, and a lot of buffering and EMI filtration of the USB data pathways. Proof of that… if you use the Link simply as a buffer between the USB output of a computer and a USB DAC, the sound of that DAC is improved significantly. It’s more upbeat, more focused, and more natural sounding. Granted there are other dedicated jitter-busters that do a similar job for less money in this context, but they cannot do all the other things the Link can do.

Those ‘other things’ include front and rear USB connections, Bluetooth (to v4.0, but not aptX HD), and Ethernet (both wired and wireless). It also includes an HDMI output if you want to display its internal web-page interface. You set the Link up this way, too, by putting it on the network and getting your computer to search for it (or you can manually find the IP address). Set-up is straightforward, as it walks you through a six-point install process, and this allows you to add Tidal, Qobuz, and Spotify accounts, switch in USB Detox (or not, if you’re weird… you can also access it from the front panel), and add and setup, network shares (music servers), Roon, UPnP and DNLA settings, Shairport-sync (for Apple devices), and so on. This is not as daunting as it sounds and is about as hard to install as it was to write.

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