Echo III Rackmount

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Creatively Expandable

Echo III Rackmount

3-slot rackmount Thunderbolt 3 to PCIe card expansion system


Connect Three Full-length PCIe Cards to Computers with Thunderbolt 3 Ports

The best portable, mini desktop and all-in-one computers feature powerful CPUs and include high-performance Thunderbolt™ ports to support peripherals. But they lack the PCIe expansion slots creative pros need to install specialty adapter cards that enable their workflows by adding video and audio inputs, transcoding data, and connecting to high-speed shared storage and networks. Sonnet has a solution—the Echo™ III Rackmount—a professional Thunderbolt™ 3 to PCIe card expansion system that enables you to connect three (up to) full-length (12.28 inches long) PCIe cards to your computer at the same time, via a single cable.

Supports Every Thunderbolt 3 Compatible, Non-GPU PCIe Card

Echo III Rackmount supports every Thunderbolt 3 compatible, non-GPU PCIe 1.1/2.0/3.0 card available including video capture and transcoding; audio DSP; 6Gb or 12Gb SAS or SATA host bus adapter; 10Gb or 25Gb Ethernet; SSD storage; and other specialty types to your system.


Do you have a card in mind but aren’t sure it’s compatible? We’ve put together a compatibility list that identifies cards conforming to Thunderbolt technology requirements, and organized by fit and power compatibility with specific expansion systems.


Avid Pro Tools Qualified

Ready for up to three Pro Tools | HDX PCIe Cards – no extra parts required

At the flick of a switch, the Avid qualified Echo III Rackmount system is instantly optimized to support up to three Pro Tools | HDX PCIe cards, with no extra parts necessary! This chassis has been tested and is qualified by Avid Audio group for use with Avid Pro Tools HD 2020 software, and Avid Pro Tools HDX and HD Native systems.

Your Entire Multi-card Pro Tools | HDX System in 4U Rack Space

Sonnet makes it easy to integrate a complete 2- or 3-card Pro Tools | HDX system and a Mac mini® in just 4U of rack space. With the rugged 1U RackMac mini rackmount enclosure plus the 2U Echo III Rackmount you can combine the power of HDX with any Avid Pro Tools hardware I/O for a complete system, including the exciting Pro Tools | MTRX Studio all-in-one audio interface.

Key Features

Adds Connectivity & Capabilities

Connects up to three high-performance non-GPU PCIe cards to your computer lacking expansion slots via a Thunderbolt 3 cable.


Broad PCIe Card Compatibility

Every Thunderbolt 3 compatible, non-GPU card supported regardless of length or height.


Pro Tools | HDX Compatible(1)

HDX compatibility mode enables use of up to three Pro Tools | HDX PCIe cards with no additional parts needed.


Three PCIe 3.0 Slots(1)

One x16 plus two x8 slots support three full-height, single-width cards, or one double-width card plus one single-width card.


Pro Power

Integrated 400W power supply with 75W auxiliary power. Saves energy by powering on/off automatically with the computer.


Remarkably Quiet

Dual temperature-controlled, variable-speed Noctua fans rated at 17dBA automatically and quietly cool the cards.


40Gbps Thunderbolt 3 Interface

Offers 2750 MB/s of PCIe bandwidth for the installed cards(1).


Two Thunderbolt 3 Ports

One port connects to computer; second port supports daisy-chaining of up to five additional Thunderbolt peripheral devices.


Rugged 2U Steel Rackmount Housing + Optional Expansion Space

Provides robust and secure protection in server and DIT racks; space for optional future expansion.

Three PCIe 3.0 Slots Plus Power to Spare

The Echo III Rackmount features one x16 and two x8 PCIe 3.0 slots(1), enabling it to support a wide variety of cards at the same time. It integrates a universal 400W power supply, plus a 75W auxiliary power connector to support especially power-hungry non-GPU cards, including the Avid Pro Tools | HDX. The Echo III was designed without a power switch, because it powers on and off automatically with the connected computer, saving energy in the long run. With no power switch, you can’t forget to turn off the system!

Built for Cool, Rackable Expansion

‍The Echo III Rackmount mounts in a rack space 2U tall, and is only 16.5 inches deep, making it ideal for use in a wide range of popular mobile racks, carts, and rack cases, and in server rooms as well. Its enclosure is formed of heavy-duty steel to provide secure mounting for the inner assembly and protection for the PCIe cards installed inside, and to support maximum airflow for cooling, regardless of where you install it in a rack.

Echo III Rackmount accommodates the PCIe cards you need for your workflow, ranging from the largest video I/O and audio transcoding cards, to the smallest Ethernet NIC and USB interface cards

Fastest External Interface Available. Thunderbolt 3 – the USB-C That Does It All

The Echo III Rackmount features a 40Gbps Thunderbolt 3 (USB-C®) interface that delivers up to 2750 MB/s of PCIe bandwidth(1), enabling it to support 4K video capture and processing cards at high frame rates, multiple audio DSPs, and 25GbE and dual-port 10GbE network cards at full performance.

Two Thunderbolt 3 Ports

One port is reserved for the connection to your computer; the second port enables expansion of up to five additional Thunderbolt peripheral devices(5) in a daisy chain.

10Gbps USB 3.2 Gen 2 Support

10Gbps USB 3.2 Gen 2 support allows you to connect a USB device(6) to the second port using the proper cable or adapter.

Supports One 5K or Two 4K Displays

Supports connecting up to two 4K @ 60 Hz displays or one 5K @ 60 Hz display.

Provides 15W of Power

For peripherals requiring extra power, 15 watts is provided to bus-powered devices.

Backward Compatible with Older Macs

No Thunderbolt 3? No problem—the Echo III Rackmount is also compatible with Macs with Thunderbolt 2 ports when used with the bi-directional Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter and a Thunderbolt cable (both sold separately).

Desktop Version Available

‍Choose between the Echo III Rackmount and Echo III Desktop to suit your workflow needs. The Echo III Desktop is wrapped in a rugged, yet lightweight aluminum outer shell, resulting in a system light enough to carry without weighing you down, yet sturdy enough to securely protect the installed PCIe cards.


Mac Compatibility


Mac with Thunderbolt 3 ports

Mac with a Thunderbolt 2 or Thunderbolt port with an Apple Thunderbolt 3 (USB C) to Thunderbolt 2 Adapter plus a Thunderbolt 2 cable (both sold separately).

macOS 10.12.6+

macOS Big Sur compatible

Windows Compatibility


PC with Thunderbolt 3 ports

Windows 10 (64-bit Edition Version 1809 or greater, see note)

Important Note: Windows computers require the latest BIOS and Thunderbolt drivers to support this product. Check with your computer manufacturer for update information.

Linux Compatibility


Linux computer with Thunderbolt 3 ports

Linux Kernel 5.0+

PCIe Card Compatibility


For a list of compatible PCIe cards, view the PDF of Sonnet's PCIe Card Thunderbolt Compatibility Chart



Part Number






Form Factor


Rackmount expansion system

External Connectors


Two Thunderbolt 3 ports

12V power port

Internal Connector


6-pin Mini-Fit Jr (same type as on legacy Mac Pro motherboard; provides up to 75W of power for PCIe cards that require supplemental power)

Expansion Slots (Facing Rear, Left to Right)(1)


One x8 mechanical (x8 electrical) PCIe 3.0

One x16 mechanical (x8 electrical) PCIe 3.0

One x8 mechanical (x4 electrical) PCIe 3.0

PCIe Cards Supported


One full-length, full-height, double-width PCIe card, plus one single-width card or

Three full-length, full-height, single-width PCIe cards

Power Supply


Universal 400W, 115-230V AC, 50-60Hz(8)

Operating Temperature


0C to 35C (32F to 95F)

Dimensions (WxDxH)


19 x 16.5 x 3.6 in. (48.3 x 41.9 x 9.1 cm)



23.15 lbs (10.50 kg)



RoHS 3 (Directive 2015/863)

IEC62368-1 and IEC62368-2

Package Contents


Echo Express III Rackmount chassis

Power cord

0.7-meter Thunderbolt 3 (40Gbps) cable

ThunderLok 3 Thunderbolt Connector Retainer Clip(2)


Support Links

Support Knowledge Base


Drivers, Documentation, FAQs

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