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We use a special USB hub called a Multi-TT USB Hub. This hub provides a dedicated TT to each port, meaning each audio interface has it's own dedicated translator from 1.1 to 2.0 giving much clearer audio when multiple repeaters are active at the same time.
Virtualizing APP-RPT and Asterisk
All services at LSR is on a single Proxmox based virtualisation system.
USB audio traffic is heavily affected by jitter and latency in the USB subsystem. As such, the USB devices connected to asterisk are connected to a dedicated PCI USB card. This PCI USB card is configured as a PCI pass-through device into the virtual machine. This removes any USB latency that may be introduced by using USB pass-through. Additionally, devices remain configured with the same device ID. This means that when multiple devices are used, USBRadio finds the same device at the same devstr. This is no longer an issue once serial based card mapping is merged into SimpleUSB and USBRadio channels.