Hysen LabsOzzy
Driver for several Ploytec interfaces
Ozzy: keeping abandoned USB audio gear alive
A reverse-engineered, open source driver that takes over support for non-class compliant USB audio interfaces and DJ mixers once their vendors stop shipping drivers.
The problem it exists for
Modern operating systems dropped support for non-class compliant USB audio devices, hardware that does not follow the standard USB Audio Class specification. Those devices always needed vendor-specific drivers, and when the vendor walks away, working professional equipment becomes unusable. Ozzy is an open source, reverse-engineered driver that steps in for non-class compliant USB audio interfaces, high-end DJ mixers, and audio processors left behind when official driver support ended. The project is written in Objective-C++ and licensed MIT.
The supported hardware
The supported devices table lists four Allen & Heath mixers, the Xone:DB4, DB2, DX, and 4D, each at 8x8 channels and sample rates up to 96 kHz, each marked as working perfectly. Why these need special handling: custom audio routing beyond simple stereo, hardware-specific DSP control and mixer integration, proprietary USB protocols for low latency, and special MIDI implementations. None of it works with a generic OS driver.
Platforms and backends
On macOS the current path is a kernel extension, delivering 8x8 audio through CoreAudio HAL and full CoreMIDI with lock-free ring buffers and sub-millisecond latency, but it requires macOS 11 or newer and a modified SIP setting. A DriverKit extension is in development, and a userspace daemon is planned. All the backends share the same CoreAudio HAL and CoreMIDI drivers, differing only in the USB communication layer. On Linux there is an ALSA kernel module with automatic transfer detection, working with JACK, PulseAudio, and PipeWire. Windows support gets a kernel-mode justification in the README, about direct USB pipe access and precise timing.
The build and signing maze
Building from source runs into Apple codesigning, and the README treats this as a real obstacle with a long troubleshooting section. A free Apple ID gives you a signing identity, no paid developer membership needed. The most common failure, the zero valid identities error, gets an extended postmortem: the WWDR G1 intermediate expired in February 2023 and broke codesigning for many developers, the trust settings trap where Always Trust silently breaks the toolchain, expired one-year certificates, and missing private keys after migration.
Architecture and limits
The architecture separates the audio engine from device protocols, so more devices can be added without touching the core. Linux and macOS implementations share the USB protocol code, and ring buffers use atomic operations for lock-free, real-time audio. The README positions Ozzy as a reference implementation, since most USB audio driver examples online are class compliant only, user-space hacks, or closed source. A support request closes the README, for anyone whose mixer the driver saved from the e-waste bin.
Editorial conclusion
The strongest parts of the README are the honest ones: a specific hardware table, a clear reason each platform needs a different backend, and a detailed account of the signing problems that greet anyone building from source.
Community notes