Network Acoustics eno2 ethernet filter

By: Chris Frankland [hi-fi+ Issue 237]

Hi-fi products often emerge from a eureka moment for their designer, which was for Richard Trussell of Network Acoustics with the original eno ethernet filter.

A trained electronics engineer, he retired from the IT industry and started selling hi-fi from home. His eureka moment came when he discovered that a better-quality ethernet cable could improve the sound, which piqued his curiosity to find out why.

In 2019 Rich got together with advertising creative and part-time cable maker Rob Osbourn. The two friends set about honing Rich’s prototype ethernet filter to produce the original eno and to form the lockdown startup they christened Network Acoustics. The eno2 I am reviewing here is a reworking of that original model, redesigned to be compatible a 1Gb/s or 100Mb/s network. It has an aluminium case instead of a plastic one, ditching the captive output lead, allowing users a choice of cable. It is supplied as standard with one of their own high-quality 0.75m streaming cable, or as Streaming System which includes an additional 1.5m length cable.

Doubters gotta doubt

Trussell says some doubters will tell you the ethernet signal is digital and thus incorruptible. Still, he points out that it is, in fact, an analogue waveform, a bit like a sine wave, and that noise can get into the cable, mix with the signal and adversely affect the sound. This noise is mainly RF, coming everywhere from sources such as wi-fi, mobile phones, TVs, satnav, Sky and many more. This noise, he says, can get onto the earth plane and interfere with the timing of the conversion process in your DAC.

The eno2 is a purely passive device and uses a new version of its proprietary eight-core electronic filtering technology to target the electrical noise without interfering with the ethernet signal. Trussell found that the thickness of the aluminium case could also hamper the effectiveness of the filter and he tried many variations until he found the thickness that most effectively shielded the circuitry from external RF interference. The box is fitted by two high-quality Neutrik RJ45 ethernet sockets and the 0.75m cable supplied uses high-purity silver/copper alloy.

As recommended, I connected the eno2 in the preferred configuration between my English Electric network switch and the Innuos Zenith MkIII streamer. Even though a network switch re-clocks the signal and has a degree of galvanic isolation, Trussell says they can add electronic noise, hence the need for a filter further down the signal path. I played the Innuos through a Pro-Ject PreBox RS2 Digital DAC, Avid Accent amplifier and Russell K Red 120Se speakers.