The Sonnet Echo III Desktop is a 3-slot desktop Thunderbolt 3 to PCIe card expansion system designed to add connectivity and capabilities to computers lacking expansion slots. It allows you to connect up to three high-performance non-GPU PCIe cards via a single Thunderbolt 3 cable. This system is Pro Tools HDX compatible in a specific mode, enabling the use of up to three Pro Tools HDX PCIe cards without additional parts. It boasts broad PCIe card compatibility, supporting every Thunderbolt 3 compatible non-GPU card regardless of its length or height. The expansion system features three PCIe 3.0 slots: one x16 and two x8 slots, which can accommodate three full-height single-width cards or one double-width card plus one single-width card. For power, it includes an integrated 400W power supply with 75W auxiliary power, and it saves energy by powering on and off automatically with the computer. Cooling is managed by dual temperature-controlled variable-speed Noctua fans, rated at 17dBA, which quietly cool the cards. The Thunderbolt 3 interface offers 40Gbps bandwidth, providing 2750 MB/s of PCIe bandwidth for the installed cards. It features two Thunderbolt 3 ports: one connects to the computer, and the second supports daisy-chaining up to five additional Thunderbolt peripheral devices. The entire system is housed in a rugged aluminum enclosure for robust and secure protection. This expansion system is ideal for creative professionals using the latest portable, mini desktop, and all-in-one computers that have Thunderbolt 4 or Thunderbolt 3 ports but lack PCIe expansion slots for specialty cards such as video and audio inputs, transcoders, or high-speed storage and network connectivity. The Echo III Desktop supports every Thunderbolt compatible PCIe 4.0, 3.0, 2.0, and 1.1 card, including those for video capture and transcoding, audio DSP, SAS or SATA host bus adapters, 10Gb or 25Gb Ethernet, SSD storage, and other specialty types.