·Review Basic Informa

·Platform: MoonAudio.com

Moon Audio is a Hi-Fi institution founded in 2003 in North Carolina, USA. It specializes in signal chain integrity, develops its own handmade cable systems, and publishes in-depth technical articles on system matching logic to help audiophiles resolve potential issues in flagship system setups. Although it operates as both a retailer and a brand, its solid engineering background and extensive real-world case studies make it a highly valuable information source within the industry.

Severing the Noise at the Source

TL;DR:

• The Matrix SI-1 is a network isolator that sits between your router and your music streamer, using active optical isolation to completely sever the electrical connection and block network noise.

• TOTL isolator in its class featuring dual femtosecond clocks, dual-fiber optical channels, and an internal power supply.

• Plug-and-play compatible with any Ethernet-connected streamer, NAS, or DAC, and pairs naturally with Matrix SS-1 Pro Network Switch.

• At $699, it's priced in the middle of the market, but outperforms devices costing two to three times more.

• Best suited for listeners with resolving systems who've already invested in quality streaming components and want to close the last gap in their signal chain.

Matrix Audio SI-1: The Missing Link Between Your Router and Your Music

Music streaming has become one of the most accessible ways to enjoy high-resolution audio. But every serious streaming setup has a weak link most audiophiles never think to address–and it's been sitting right between your router and your music streamer the whole time. That Ethernet cable running from your router? It's carrying more than music. It's carrying noise, electromagnetic interference from your router, switch, and every other device on your home network. And that noise has a direct path into your audio chain.

Matrix Audio, a hi-fi company that has spent the last several years building out one of the most thoughtful lineups of network audio products on the market, is betting that serious listeners are ready to address that blind spot. Their answer? The SI-1 Audio Grade Network Isolator–a compact, purpose-built device designed to sit at the very end of your network chain, right before your music streamer, and sever the electrical connection between your noisy home network and your clean audio signal path.

PROS

• Incredible value for money, combining isolation, clocking, and power supply into one chassis

• Internal linear PSU eliminates the irony of most isolators; keeps the signal path clean from the inside out

• Dead-simple integration: one Ethernet in, one Ethernet out

The Problem the SI-1 Solves

In any streaming setup, the network connection is paramount. It's both the source of music and a potential source of contamination. Without a stable network connection, you won't be able to reap the benefits of streaming–you might as well not stream at all. We've always emphasized the value of a wired network connection over a wireless one, regardless of the components used or the setup itself. But even a wired network connection doesn't guarantee you a problem-free listening experience.

Matrix Audio SI-1 connected to NT-1 back panel view

Routers and network switches generate EMI and RFI. Ground potential differences between devices can create ground loop noise. Power supply noise from network hardware can bleed downstream, and crosstalk between signal pairs in standard Ethernet cables can further degrade signal integrity. None of this is controversial — it's basic electrical engineering. The question has always been how much of that noise actually makes it through to affect what you hear, and how we address it to yield audible improvements. The SI-1 enters the picture targeting three core functions: galvanic isolation against network noise, optimized digital signal transmission, and surge protection for downstream equipment.

By incorporating a network isolator into your hi-fi system, you're blocking EMI/RFI generated by routers and switches from entering the audio system. It will eliminate power supply noise from network devices, resulting in a cleaner and darker background.

How the SI-1 Works

The Matrix Audio SI-1 achieves comprehensive sound quality improvement through a suite of core technologies:

• Active optical-electrical isolation technology, eliminates noise from network transmission

• Dual-channel optical fiber transmission with independent transmit and receive paths

• Dual-winding epoxy-potted toroidal transformer with multiple LDO linear power supplies

• Dual femtosecond clocks

• 2x 1 Gbps gigabit RJ45 ports: one input port and one isolated output port

• Front-panel connection status indicator, making the working status clear at a glance

• Physically separated RJ45 ports, dedicated isolation washer on the output port

• Full CNC enclosure, Matrix Design language

Active Optical-Electrical Isolation

The SI-1's active optical electrical isolation technology sets the foundation for its performance, effectively blocking electromagnetic interference generated by routers and network switches. It accepts a standard RJ45 Ethernet connection from your network on its input port, and internally that electrical signal is converted into an optical signal via two specialized optical transmitters–one handling upstream data, one handling downstream. Unlike SFP-based solutions that still rely on external modules and their own potential noise contributions, the SI-1's optical conversion is fully integrated and optimized within the chassis.

Matrix Audio SI-1 back panel view

By converting to light, the SI-1 breaks the direct electrical connection between your network and your audio equipment. There's no path for noise to travel. The galvanic isolation is complete. On the output side, the optical signal is converted back to electrical and sent to your streamer through an isolated RJ45 port. That output also features a physical electrical isolation washer, reinforcing the separation and cutting off electrical continuity between devices.

Matrix Audio SI-1 circuit board

By purifying network noise that can interfere with audio signals, this technology breaks ground loops and prevents current noise caused by grounding potential differences between devices.

The Clock

Matrix Audio SI-1 internals close up of clocks

Timing is everything in any digital audio setup, and jitter–those annoying timing inaccuracies in the data stream–is the enemy. The SI-1 incorporates dual femtosecond clock circuits to mitigate potential timing errors. Not only are femtosecond clocks an incredible choice on Matrix's part, but having two of them means the SI-1 is actively rebuilding the network signal with superior timing accuracy rather than simply passing through whatever your router handed it.

Power Supply: Internal and Linear

Here's another area where Matrix Audio made a great engineering choice. Most network isolators on the market are passive devices meaning they don't have their own power supply and draw whatever they need from the network signal, or they ship with an external switching power supply. Switching power supplies themselves are a source of noise, which defeats the purpose of a noise isolation device.

The SI-1 uses an internal linear power supply built around a dual-winding epoxy-potted toroidal transformer feeding multiple independent LDO regulation circuits. This provides clean, stable DC voltage to the optical transmitters and femtosecond clocks without introducing new noise into the equation. Sure, it's a more expensive approach, and it's why the SI-1 requires an AC power connection and consumes up to 15W, but it's a smart approach. The device isn't compromising its own performance with a noisy power source–it's generating its own clean power from the ground up.

Matrix Audio SI-1 toroidal transformer

The Big Picture: Design & Specs

Matrix Audio SI-1 chassis photo

The SI-1 follows Matrix Audio's design philosophy–clean, minimal, and understated. The chassis was expertly crafted, featuring a CNC-machined unibody aluminum enclosure. Not only is it premium looking, but it has a purpose far greater than looks: enhanced shielding against external interference.

The unit itself is rather small at 4.72" x 8.07" x 1.73", so it won't take up a lot of space in your existing setup. As for weight, at 3.4 lbs, if you have to move it around, it won't cost you a day out of work.

Matrix Audio SI-1 front panel view

Matrix Audio SI-1 back panel view

This isn't the device with a thousand buttons and fancy functions on the front panel. Why? Because it doesn't need it. On the front panel sit three LED light indicators–one for power and one for each link status–alongside the Matrix Audio logo. The back panel continues that minimalist mindset with only what you need and nothing more. Two RJ45 ports–intentionally separated with the input on one side and the output on the other–a switchable button to switch off the Ethernet port LEDs on the front panel (a thoughtful touch that eliminates light pollution in a darkened listening room) and the power port.

Where it Fits In Your System

While it might seem daunting at first, integrating the SI-1 into your system is simple and painless. On the input side, the SI-1 needs to be directly connected to your modem/router. The output will be used to connect the SI-1 to your source device, such as your dedicated music streamer or network player. In the simplest terms possible: the SI-1 sits between your network router and streamer. It's the last step in your network chain before the music streamer.

In a simple setup, the signal path looks like this: Router → SI-1 → Music Streamer.

Matrix Audio SI-1 network signal chain diagram

If you're also running a NAS or Roon Core server, you could place a second SI-1 between your switch and that device–but that's only if you think you need it. Now if you want to get fancy with it (or maybe already own one), you can add the Matrix Audio SS-1 Pro or SS-1 Network Switch into the mix. It would look a little something like this: Router → SS-1 Pro → SI-1 → Music Streamer. The switch handles signal regularization and serves as the hub of your network; the isolator handles the final stage noise elimination right before the streamer. They're complementary devices.

Matrix Audio SI-1 and SS-1 Pro network signal chain diagram

The SI-1 is designed to work intuitively with other Matrix Audio components–pair it with a streamer like the Matrix Audio NT-1, and you're harnessing the power of a full Matrix ecosystem, but that doesn't limit you to only their gear. The SI-1 is also compatible with a slew of other high-end brands of streamers, NAS drives, media servers, and other equipment with Ethernet connectivity. So whether that's your trusty music streamer or beloved audio-grade network switch from another brand, no problems there.

Verdict

If you're asking yourself, "Who is the SI-1 for?" here's the answer. Anyone who has already invested in a quality streaming chain–a capable streamer, a good DAC, a serious amplifier, that favorite pair of speakers–and is looking to optimize the signal path feeding it all. If you've built a resolving system and you're chasing that last percentage point of background blackness, detail retrieval, and timing precision, the Matrix Audio SI-1 Network Audio Grade Isolator addresses those problems.

It's one of those hi-fi components that makes you wonder how you ever listened without it. For anyone building a high-resolution streaming system, this is the piece that quietly does the most important work: getting out of the way so your music can breathe.