·Review Basic Information

·Platform: AudioArt

AudioArt Magazine has been growing alongside countless music lovers and audiophiles since its founding in 1988. Each monthly issue of the magazine covers a wide range of the latest developments in music and audio, featuring in-depth reviews of the newest audio equipments from around the world, system adjustment techniques, guides to the latest music softwares, as well as introductions to music genres, composers, and interviews with renowned musicians.

Original: AudioArt, Vol. 451, April 2026

Review Product:  「Matrix Audio」SI-1 Audio Grade Network Isolator

The article is as follows:

The most satisfying audio streaming accessory I've tested recently

「Matrix Audio」 SI-1 Audio Grade Network Isolator

Looking at all audio streaming devices, I believe a well-designed audio-grade network switch is absolutely worthy of being the first audio component you prioritize upgrading when seriously building a streaming audio system. It not only ensures that the digital signal is in a relatively "healthy" state before actually entering the music server or streamer, allowing the backend audio device to perform digital interface conversion or D/A conversion; moreover, an audio-grade switch stands at the forefront of the streaming path, directly acting as a firewall against numerous noise interferences for the audio system. If the criterion for judging an audio system is what's often said: the strongest performance depends on the weakest link, then I believe that filling this gap with an audio-grade switch is what truly unlocks the maximum value of the streaming DAC. While the Matrix Audio SI-1 reviewed here isn't exactly an network switch, it only has one input and one output Ethernet ports on the back, but it functions quite similarly to an network switch. Firstly, it isolates network noise for the streamers, secondly, it further reduces streaming jitter through a built-in clock. Therefore, the manufacturer has given it this very accurate name: "Audio Grade Network Isolator".

*The following text is presented for your convenience:

SI-1 Audio Grade Network Isolator, abbreviated as SI-1

The chassis is made from a solid aluminum block.

When I first saw the SI-1 in person, several aspects immediately caught my attention.

First, despite its compact size, the chassis is carved from a solid block of aluminum. The moment you pick it up, it feels almost like a brick — dense and reassuringly heavy. Such a substantial enclosure not only provides comprehensive shielding against noise interference, but also delivers excellent vibration suppression. Considering the price of the SI-1, the fact that the manufacturer was willing to invest in such a serious chassis design is something I honestly had not encountered before.

Second, although the rear panel of the SI-1 only features two network ports, I actually do not see this as a disadvantage. Think about it: many so-called audiophile network switches offer an entire row of Ethernet ports on the back, yet in real-world audio systems, most users only utilize two ports — one input and one output. The remaining unused ports simply go to waste. The SI-1 takes a very focused and precise approach. Beyond its advantage of being compact and space-saving, its one-in/one-out network configuration is clearly designed around the mainstream usage habits of streaming audio enthusiasts. The input and output are explicitly designated, meaning the signal path has already been “optimized” by the manufacturer. This is an exceptionally clever design choice, and one of the reasons why I appreciate the SI-1 so much.

Optical Isolation, Dual Femtosecond Clocks

So how does the SI-1 isolate streaming-related noise?

The SI-1 employs Matrix Audio’s latest proprietary active optical isolation technology. Internally, the circuit incorporates two independent optical transmission systems, forming a dual-channel architecture that completely separates the signal input and output paths. This dramatically reduces the possibility of mutual interference between incoming and outgoing signals. Through optical isolation, streaming noise can be effectively eliminated. At the same time, it also helps prevent electrical noise caused by improper grounding between audio components. Inside the SI-1 are two highly precise femtosecond clocks. These clocks help ensure the integrity of the streaming signal while reducing jitter and timing errors.

From this perspective, the SI-1’s solid aluminum chassis design makes perfect sense. Femtosecond clocks are extremely sensitive to temperature fluctuations during operation. Even the slightest thermal variation can alter the oscillation frequency of the clock and affect its precision. By enclosing the entire circuitry within a solid aluminum housing, the manufacturer is effectively helping maintain a stable internal temperature environment, maximizing clock synchronization accuracy.

The SI-1’s power supply design is equally sophisticated. It uses a traditional linear power supply built around a low-noise toroidal transformer with dual windings, combined with multiple stages of voltage regulation to ensure exceptionally clean and stable power delivery. Even the output network port is equipped with insulating washers for electrical isolation. This not only helps maintain signal transmission stability, but also effectively prevents short circuits caused by sudden current surges, protecting downstream digital audio devices from potential damage.

The Effect Is Excellent

This listening session took place in our publication’s Listening Room No. 2 using two different systems.

The first system paired the Atlantis Lab AT21 Pro speakers with a Naim Uniti Star streaming amplifier. The second system used the limited-edition ATC SCM20ASL active speakers together with the COS D10 V2 streaming DAC.

In both systems, the SI-1 delivered extremely positive results, and the level of improvement exceeded my expectations. Calling it merely a “streaming accessory” almost feels unfair. In actual performance, I believe it competes directly with the audiophile network switches we commonly use in-house. That surprised me greatly, because at the SI-1’s asking price, simply achieving parity would already have been impressive enough.

So what exactly does the SI-1 improve?

First, the sound gains greater body, solidity, and focus. When listening to chamber music, even recordings featuring only violin and piano no longer sound lightweight or diffuse. Instead, the presentation becomes tangible, dimensional, and richly detailed, creating a stronger sense of intimacy between the listener and the music. It is the kind of improvement that immediately draws you in.

Second, after introducing the SI-1 into the system, the audio stream sounded remarkably stable and composed. The background became noticeably darker and quieter, while subtle violin nuances and low-level details were reproduced with exceptional naturalness. This sense of calmness, stability, and enhanced tonal density allowed the SI-1 to demonstrate a more complete and mature sonic performance than many audiophile switches within the same price category.

• The SI-1 employs active optical isolation technology internally. Both the input and output stages of the digital signal utilize independent optical transmission systems, complemented by a carefully engineered power supply design and meticulously selected capacitors. Together, these elements form the key foundation for improving streaming audio quality.

The day after the initial listening session, I returned to the listening room and noticed that the SI-1, having been left powered on overnight, was slightly warm to the touch. I replayed the same tracks I had listened to the previous day, and sure enough, the performance had improved even further.

The most noticeable improvement was the increased sense of quietness in the sound. Even at higher listening volumes, the presentation never became harsh or fatiguing. The tonal character also became warmer and more natural. When listening to cello recordings, I could vividly sense the warm resonances of the instrument’s body at close range, combined with the cello’s inherently rich and full-bodied tonal lines — the kind of sound that is instantly appealing to almost anyone.

That day, I listened to French pianist David Fray performing Mozart: Piano Concertos Nos. 22 & 25. I found that the SI-1 presented a soundstage that was somewhat more intimate and forward in perspective, yet the layering and image placement remained exceptionally well defined. Compared to some significantly more expensive audiophile network switches I have personally heard, there was still a slight difference when it came to recreating that expansive soundstage depth that appears to extend endlessly backward.

I believe, multiple SI-1 units can be cascaded together. Using several SI-1 units simultaneously — or alternatively upgrading to Matrix Audio’s own SS-1 Pro Audio Grade Network Switch — would likely deliver an even more comprehensive soundstage presentation.

My Favorite Streaming Accessory in Recent Memory

After spending time with the SI-1, I was genuinely surprised that it introduced an entirely different approach to audiophile networking.

It is smaller in size, yet its improvement to streaming performance is even more pronounced. Once I realized that my streaming system only truly required a single network input and output, the SI-1’s design philosophy — concentrating all available resources and budget into executing one specific task to the fullest — actually proved more effective at maximizing streaming performance.

And once I could clearly hear the changes the SI-1 brought to the system, it became very difficult to remove it from the setup.

High-end audio equipment rarely survives direct comparison unscathed, and among the streaming accessories I have tried recently, this is easily one of the most satisfying.