Matrix Audio SI-1

The Ethernet cable that connects your router to your network player carries far more than music. Electromagnetic noise, ground loops, interference from household equipment: all these invisible forms of pollution travel with the signal all the way to the audio conversion stages. With the SI-1, Matrix Audio offers a radical answer to this problem by cutting any electrical link between the home network and the hi-fi system thanks to complete galvanic isolation via optical fiber.

Cut the electrical cord, not the data flow

The SI-1 is based on an internal conversion of the Ethernet signal into an optical signal, followed by its reconversion into an electrical signal at the output port. This break in galvanic continuity physically prevents interference, electrical noise, and ground potential differences from propagating to connected audio equipment.

Inside the device, two separate optical channels handle data transmission and reception. This separation avoids crosstalk between upstream and downstream streams, a point often overlooked in passive isolators using magnetic transformers. The output port includes an additional insulating washer to reinforce the electrical separation between the two sections.

A power supply designed like that of a DAC

The SI-1 features its own internal linear power supply, an uncommon technical choice for this type of device. The dual-winding toroidal transformer is encapsulated in epoxy to limit mechanical vibrations and electromagnetic leakage. Several low-noise LDO (Low Drop-Out) regulators then power the optical circuits and clocks.

Two femtosecond clocks synchronize data transmission. Their precision is intended to reduce network jitter and timing errors that can affect downstream audio signal reconstruction, even if the streamer has its own reclocking system.

Matrix Audio recommends using a three-conductor power cable with a reliable ground connection. Without proper grounding, a slight tingling sensation may be felt when touching the metal chassis, a common phenomenon with devices using a linear power supply without grounding.

A compact format that hides its complexity

With dimensions of 120 × 205 × 44 mm and a weight of 1.54 kg, the SI-1 adopts the visual language of other Matrix Audio products: a one-piece CNC-machined aluminum chassis, straight lines, understated finish. The perforated sides ensure passive ventilation of the internal circuits. The manufacturer recommends leaving at least 5 cm of free space around the device and not obstructing the vents.

The front panel displays three LEDs: one for power, two for the connection status of the input and output ports. At the rear, each RJ45 port has two LEDs indicating connection speed and network activity. The green LED stays on continuously for a Gigabit connection, and turns off for 10/100 Mbps connections. The yellow LED flashes during data transfers. A button allows all rear LEDs to be turned off with a single press, a welcome detail in a listening room where any light source can be distracting.

Note the absence of an on/off button: the device operates as soon as it is plugged in. The chassis becomes slightly warm during operation (power consumption below 15 W).

Where should the SI-1 be placed in your setup?

Two main configurations emerge from Matrix Audio’s recommendations:

Directly before the network player or the DAC equipped with an Ethernet input. The SI-1 then isolates a single device from the rest of the home network. This is the simplest and most direct configuration.

Between the router (or a generic switch) and a dedicated audio switch such as the SS-1 or SS-1 Pro from Matrix Audio. The SI-1 then serves as an isolation point for the entire audio network, upstream from the other equipment. According to Matrix Audio, this position at the head of the audio chain delivers the best results.

The SI-1 works with any audio equipment featuring a wired Ethernet connection, regardless of brand: network players, music servers, connected DACs, NAS units. Network compatibility covers IEEE 802.3 standards up to Gigabit Ethernet (10/100/1000 Mbps).

Built-in electrical protection

Beyond audio isolation, the SI-1 protects connected equipment against electrical surges. The optical isolation blocks voltage spikes that could travel through the Ethernet cable during storms or disturbances on the electrical network. The manufacturer mentions protection against lightning, power surges, electrostatic discharges, and mains noise. For expensive audio equipment, this secondary function is not insignificant.

Technical specifications

Signal purity and isolation

• Sonic Purity: purified signal path to maintain sonic authenticity
• Network noise isolation: blocking electromagnetic interference from routers and switches
• Dual optical channel: independent transmit and receive paths to avoid crosstalk
• Femtosecond clocks: two ultra-precise clocks for optimal timing
• Physical isolation: insulating washer on the output port to prevent current noise and ground loops

Power supply

• Type: linear power supply with dual-winding toroidal transformer and multiple low-dropout regulators (LDO)
• Voltage: AC 100–120 V 50 / 60 Hz or AC 220–240 V 50 / 60 Hz (factory setting)
• Power consumption: less than 15 W

Protection

• Protection against lightning, overvoltage, electrostatic discharge, and mains noise

Standards and protocols

• IEEE 802.3: 10BASE-T
• IEEE 802.3u: 100BASE-TX
• IEEE 802.3z: 1000BASE-T
• IEEE 802.3ab: 1000BASE-T

Ports

• Input: 1 × RJ45 10 / 100 / 1000 Mbps
• Output: 1 × RJ45 10 / 100 / 1000 Mbps (photoelectric isolation)

LED indicators

• Front panel
  • 1 LED for power
  • 2 LEDs for link status
• Rear panel (LAN ports)
  • 2 LEDs per port for speed, link, and activity
  • Switchable Ethernet port LEDs to limit light pollution

Performance

• Maximum number of MAC addresses: 2000

Design and construction

• One-piece CNC-machined aluminum enclosure for durability and shielding against electromagnetic interference
• Controllable LEDs: LAN port indicators can be turned off to reduce light pollution
• Dual optical channel with femtosecond clocks and linear power supply

Dimensions and weight

• Width: 120 mm
• Depth: 205 mm
• Height: 44 mm
• Weight: 1.54 kg

Included accessories

• Power cable × 1
• User manual × 1
• Warranty card × 1