Stack Audio Smooth-LAN Regenerator network filter
Stack Audio first hit the scene with a streamer, a product that never really came to fruition but which lead to the rather more affordable Link streamer and its successor the Link II. Today Theo Stack and his crew are making streaming accessories that inhabit the brand’s trademark machined aluminium casework and look like far better value than the competition because of it. Last year we tried the Smooth-LAN network filter, a small in-line device that Chris Baillie found to be very effective at relaxing the sound of his streaming system.
This year Stack has upped the ante with the Smooth-LAN Regenerator, an active noise filter with in- and outputs usefully placed at one end of another beautifully machined bit of casework. The Regenerator is a two part case with no fewer than 36 small screws holding the two halves together, this degree of clamping is required to ensure that there’s not even the smallest gap between the nine compartments within what is a pretty compact case about (about four inches long). Each compartment contains either filtering or reclocking circuitry and these are both highly sensitive to EMI (electromagnetic interference) as well as being inclined to produce the stuff, so if you can keep this energy from straying it should help the end result.
The Regenerator is not just designed to control its own emissions, it is primarily intended to remove noise from the network that feeds a streamer, noise that typically produces the hard, grainy sound that we associate with bad digital. While streamers have many advantages over CD players they are susceptible to the electrical pollution produced by all of the devices on an internet network and beyond, typically this is produced by traffic between devices like smart TVs and speakers but includes anything that connects to the internet. Removing this noise brings significant benefits as we have discovered with network filters in the past, but none of these have been regenerators. There is another example on the market made by Uptone in the US but surprisingly this is the first in quite a long time.
The active element of this device consists of resynchronization/re-timing of the incoming data, it requires its own clock to achieve this, and combines the process with passive filtering at both in- and outputs. The clock naturally has its own cavity within the metalwork in order to keep interference at bay. Stack provide a 50cm ethernet cable with the Regenerator in order to make the connection between the filter and the streamer.
The Regenerator runs off a custom low noise power supply of the switching persuasion, this is a plug-top type with a removable cable that’s terminated in a USB C plug that provides 5V for the filter. Each circuit block within the device has its own power supply and the clock is further isolated to keep phase noise and jitter as low as possible.
All of which makes the Regenerator look like remarkably good value when you look at the alternatives on the market, these are nearly all passive devices and many have plastic cases. I asked Theo how he can achieve the £750 price of this unit and was told that they have lower margins than most, plus they sell direct which always helps.
Sound quality
I tried the Stack filter with a number of streaming devices to get a feel for it and see if the results changed with different components, generally however the same thing tended to happen every time. Putting the Regenerator between the incoming ethernet connection and a streamer makes the sound more relaxed without taking away snap or immediacy, essentially by lowering noise it makes everything cleaner so that you can hear what’s going on more clearly. Essentially you don’t hear the impact of the noise floor to the same degree because it has dropped.
With my Melco N10 server playing Dylan’s Tangled Up in Blue from Qobuz adding the Regenerator improved timing, created greater contrast between what the various musicians are doing and brought an ease to the proceedings that made it sound more natural. The kick drum became more precise as did the attack on the guitar, even the voice sounded less woolly. With Ike White’s Changin’ Times the bass developed greater power and the guitar had more edge much like the Dylan, what this did to the music was to make it more engaging and enjoyable. The sense of three dimensionality also increased especially on the vocal which is the focus of this song, but at the same times it was easy to separate out what the band members were contributing because the presentation was more open and clear.
With the Electrocompaniet ECM 1 MkII playing June Tabor’s version of Love Will Tear Us Apart the imaging benefits of the Regenerator were more tangible, her voice really projected into the room and the expressiveness she brings to the piece was made all the more clear. It sounds as if the sharp edges have been removed which allows the true nature of the recording to be heard, it’s a cleaner window into the music that makes it sound more real. Drummer Camille Bigeault’s extraordinary optometric precision on the tune Mental Web is made that much easier to follow by this filter, the track is a piece of math rock where the tempo weaves a kind of magical spell that is extraordinary, the Stack filter takes it from being a display of virtuosity to a piece of highly engaging music. The DAC, amp and speakers have to be up to the job as well of course but the source is critical and this device really helps it out.
I like the way that the soundstage opens out when you drop the Regenerator into the ethernet line, this happened more distinctly than usual with Keith Jarrett’s The Old Country (More from the Deer Head Inn), this is a good live recording and contains many cues about the space in which the performance took place. These cues are not apparent with a direct connection to the router however, it takes a filter like this to cut out the noise that swamps such detail. The information that tells you about the space around the performers is at a lower level than the notes they are playing, low enough for it to be smothered in the (inaudible) noise floor, but when that floor is pushed down such details appear and combine with the fundamental sounds to produce a larger overall picture. Now the various contributions of the three musicians are much better developed, they project in a three dimensional fashion and are once again much more real.
With an Innuos Zenith SE server/streamer the addition of the Regenerator brings about a reduction in perceived grain, the sound becomes smoother and more analogue like with an easier flow. Stephen Stills’ So Begins the Task goes from being fabulous to sublime, close your eyes and connect sublime. With the more energetic Ramblin’ by the Ginger Baker Trio you get more vitality and immediacy, essentially more of what is on the recording comes through and the sound is that much more enthralling as a result.
Conclusion
Stack Audio always appear to give you more for your money than most in material terms and in our experience this results in worthwhile upgrades in sound quality That is very much the case here, the Smooth-LAN Regenerator is a well executed and nicely finished active network filter that benefitted every source I had the opportunity to try it with, if you have a decent streaming system but are not using something to keep the noise at bay I highly recommend giving it a spin.