Searching for a "support link" usually leads to third-party file repositories or community forums. Because the official activation servers are offline, installing the software today often requires finding the specific "keygen" or patch files that were archived by the community, which comes with the standard risks of downloading legacy, cracked software (viruses, malware, etc.).
Official SRS Audio Sandbox typically supported onboard audio chips (Realtek, SigmaTel, IDT) and PCI/e soundcards. However, version 1.9.4—likely a circulated on forums like Ru-Board or FileCatalog —claimed to add explicit support for USB soundcards (e.g., Creative X-Fi USB, Logitech USB headsets, external DACs). srs audio sandbox 1904 with usb soundcard support link
Because SRS Labs was acquired by DTS, this software is no longer officially sold. You can typically find the 1.9.0.4 installer on legacy software archives such as: Cnet Download Archive Internet Archive (Wayback Machine) Revisiting a Legend: SRS Audio Sandbox 1