Open Apollo

Open-source Linux driver and tools for Universal Audio Apollo Thunderbolt and USB interfaces

Open Apollo brings Linux support to Universal Audio's Apollo audio interfaces. Built through clean-room reverse engineering, this community-driven project provides a native kernel driver for Thunderbolt models and a pure-userspace stack for USB models, along with a mixer daemon and system tray indicator.

⚠️ Experimental — This project is under active development and not yet ready for production use. Expect rough edges, kernel stability issues on some configurations, and incomplete features. We're shipping early to get community feedback and testing across different Apollo models.

What Works (Apollo x4 — Thunderbolt, Ubuntu 24.04)

Full duplex audio — 4 analog inputs + 6 analog outputs verified (24/22 total ALSA channels exposed; S/PDIF, ADAT, and virtual channels are unverified)
All sample rates — 44.1, 48, 88.2, 96, 176.4, 192 kHz
Preamp control — gain, 48V phantom power, PAD, low cut, phase invert, mic/line switching
Monitor control — volume, mute, dim, mono, talkback, headphone routing
DSP mixer — input faders, pan, sends (AUX1/AUX2, CUE1/CUE2), solo, mute
PipeWire virtual I/O — named Mic 1-4, Line In 3+4, Monitor L/R, Line Out devices
Desktop audio — YouTube, system sounds, GNOME volume control all work through Apollo Monitor
WebRTC capture — clean audio in Chromium-based browsers (webcam mic tests, Discord web)
pw-record/pw-play — zero-dropout capture and playback verified
Guided installer — sudo bash scripts/install.sh with hardware validation gates + audio test
System tray indicator — real-time hardware status

What Works (Apollo Solo USB)

Confirmed working on Ubuntu Studio 24.04 / Intel Tiger Lake-H by contributor @stoneiboyz-sys:

6ch playback — S32_LE 48kHz, confirmed on Ubuntu Studio 24.04 (Intel) and CachyOS (AMD)
10ch capture — confirmed working; one-shot usb-full-init.py (38 packets, includes DSP program load), then modprobe snd_usb_audio
PipeWire capture — mic input working end-to-end; Discord voice calls, pw-record, browser tabs confirmed
Hardware monitoring — mic → headphones simultaneous with active PipeWire streams
Preamp control — gain, 48V phantom power, mic/line switching via vendor control
Monitor control — level, mute, mono
PipeWire playback — browser audio, system audio, DAWs all work
Patched snd-usb-audio — four out-of-tree patches (fixed-rate quirk, implicit feedback skip, endpoint compat bypass, IFACE_SKIP_CLOSE)
Automatic init via udev — firmware upload + full DSP init on device plug-in; no daemon required

USB Known Issues

Issue	Status	Notes
Full init crash at packet 28	Known	Some firmware builds crash on IIR biquad SRAM write (address mismatch); observed on CachyOS/AMD (@ariahello) with a different Cauldron build. Playback still works
Intel xHCI EP6 flood	Resolved	One-shot `usb-full-init.py` stabilizes device; EP6 drain daemon removed from stack
PipeWire capture zeros	Fixed	Resolved by `QUIRK_FLAG_IFACE_SKIP_CLOSE` patch (quirks.c, patch 4) — prevents snd-usb-audio from resetting Interface 3 on stream close
DSP init ordering	Documented	`usb-full-init.py` runs before `modprobe snd_usb_audio`; reversed from previous documentation

{% callout type="note" %} USB support uses sudo bash scripts/install-usb.sh. See USB Quick Start below. {% /callout %}

Known Issues

Issue	Severity	Workaround
Firefox Snap crashes — kernel `hrtimer` lockup when using WebRTC capture	Critical	Use Chromium or Firefox .deb instead of Snap
Raw pro-audio node crash — apps selecting "Apollo x4 Pro" (22ch) as input can hang the system	Critical	Default source is set to Mic 1; avoid selecting the raw multichannel device
WebRTC capture pitch drift — brief pitch wobble (~1-3s) when browser capture starts; stabilizes automatically. This is normal PipeWire DLL lock-in behavior affecting all pro-audio interfaces through the PulseAudio bridge.	Minor	Normal — wait for it to stabilize. Native PipeWire apps (`pw-record`, Ardour, OBS) have zero drift.
Apollo hot-unplug — powering off Apollo while driver is loaded	Fixed	Shutdown guards prevent crash; system stays stable (#22)
Ardour JACK routing — Ardour via JACK can steal ALSA device from PipeWire	Moderate	Launch with `pw-jack ardour7`; restart PipeWire if audio stops
Audacity ALSA-only — Ubuntu's Audacity package lacks PipeWire backend	Minor	Install Audacity via Flatpak for PipeWire support
GNOME Sound Settings — input level meter may not show activity	Cosmetic	Audio works; meter is a GNOME UI limitation with pro-audio devices
Warm reboot requires Apollo power cycle — rebooting Linux while Apollo stays powered leaves firmware in a stale state; audio won't work until Apollo is power-cycled	Moderate	After reboot: turn Apollo off, wait 5s, turn back on. Hot-replug auto-recovers within ~7s. Cold boot (Apollo powered on after Linux) works without issues.

App Compatibility

App	Status	Notes
Chromium / Chrome	Verified	Recommended browser for WebRTC capture
Firefox .deb	Untested	Should work; Snap version crashes (see Known Issues)
Discord .deb	Verified (USB)	Voice calls with mic input confirmed on Apollo Solo USB (Ubuntu Studio 24.04)
OBS Studio	Untested	Should work natively with PipeWire
Ardour	Partial	Use `pw-jack ardour7`; don't let it grab ALSA directly
Audacity	Partial	Flatpak version only (Ubuntu .deb lacks PipeWire backend)
pw-record / pw-play	Verified	Zero-drift, cleanest capture path
REAPER	Untested	Expected to work via `pw-jack`

Recommendation: Use Chromium-based browsers for WebRTC. Use native PipeWire apps (pw-record, Ardour, OBS) for studio-quality recording with zero clock drift.

Not Yet Implemented

Virtual/monitor loopback, console UI, multi-device support, plugin chain (UAD plugins require PACE licensing — not planned)

Supported Devices

Thunderbolt Models

Device	Status
Apollo x4	Partially Verified — analog I/O (Mic 1-4, Monitor, Line Out), preamps, gain, DSP settings. S/PDIF, ADAT, virtual channels untested.
Apollo x4 Gen 2	Needs Testing
Apollo x6 / Gen 2	Needs Testing
Apollo x8 / Gen 2	Needs Testing
Apollo x8p / Gen 2	Needs Testing
Apollo x16 / Gen 2	Needs Testing
Apollo x16D	Needs Testing
Apollo Twin X / Gen 2	Needs Testing
Apollo Solo (Thunderbolt)	Needs Testing
Apollo 8P (original)	Needs Testing
Arrow	Needs Testing

All Thunderbolt Apollo models share the same register map and protocol — the driver includes device detection and channel configuration for every model listed above. We need community testers to verify each one.

USB Models

Device	Status
Apollo Solo USB	Verified — USB, playback + capture, preamp control, PipeWire integration
Apollo Twin USB	Needs Testing
Apollo Twin X USB	Needs Testing

Thunderbolt 2 Devices (Not Supported)

Older Apollo models with Thunderbolt 2 connections (Apollo Twin, Apollo 8, Apollo 16, Apollo Duo, Apollo Quad) are not expected to work, even with an Apple Thunderbolt 2 → 3 adapter.

The issue is not the driver — it's that Linux does not enumerate Thunderbolt 2 PCIe devices in most configurations. The Apollo will not appear in lspci output, so the driver has nothing to bind to. This has been confirmed by a community member testing an Apollo Twin (TB2) with an Apple adapter on a Linux laptop with Thunderbolt 3 ports — the install completed successfully but the device was never detected.

If your Apollo uses a Thunderbolt 2 connector (Mini DisplayPort-shaped, not USB-C), you will likely hit this limitation. This project targets Thunderbolt 3/4 Apollo models (USB-C connector) on systems with native Thunderbolt 3 or 4 ports.

Quick Start

Prerequisites

Ubuntu 24.04+, Fedora 40+, Arch, openSUSE Tumbleweed, Linux Mint 22, Pop!_OS 24.04, Manjaro
Linux kernel 6.8+ with headers installed (required — uses hrtimer_types.h introduced in 6.8)
Thunderbolt 3 or 4 connection (see Thunderbolt 2 note below)
GCC, Make
Python 3.10+ (for mixer daemon)
iommu=pt kernel parameter required on most systems (see below)

Install

git clone https://github.com/rolotrealanis98/open-apollo.git
cd open-apollo
sudo bash scripts/install.sh

The installer is a guided walkthrough that:

Installs dependencies, builds the driver, sets up DKMS
Deploys PipeWire/WirePlumber/UCM2 configs
Guides you through an Apollo power cycle for clean Thunderbolt initialization
Loads the driver, verifies DSP handshake, sets up virtual I/O devices
Starts the mixer daemon and tray indicator
Plays a test tone so you can verify audio output

NixOS (Thunderbolt)

Add to your flake.nix inputs:

inputs.open-apollo.url = "github:rolotrealanis98/open-apollo";

Then in your configuration.nix:

imports = [ inputs.open-apollo.nixosModules.default ];
hardware.ua-apollo.enable = true;

Run nixos-rebuild switch — the module handles the kernel module build, iommu=pt, Thunderbolt (bolt), PipeWire, and required packages.

Uninstall

sudo bash scripts/uninstall.sh

Removes driver, DKMS, all configs, services, and guides you through Apollo power-off for clean module unload.

Troubleshooting

If audio stops working after using a JACK app (Ardour, etc):

systemctl --user restart pipewire wireplumber pipewire-pulse
apollo-setup-io

Virtual I/O devices (Apollo x4)

After running apollo-setup-io, these devices are available in PipeWire:

Device	Type	Channels
Apollo Mic 1	Source (capture)	Mono
Apollo Mic 2	Source (capture)	Mono
Apollo Mic 1+2	Source (capture)	Stereo
Apollo Mic 3	Source (capture)	Mono
Apollo Mic 4	Source (capture)	Mono
Apollo Line In 3+4	Source (capture)	Stereo
Apollo Monitor L/R	Sink (playback)	Stereo
Apollo Line Out 1+2	Sink (playback)	Stereo
Apollo Line Out 3+4	Sink (playback)	Stereo

USB Quick Start (Apollo Solo USB)

git clone https://github.com/rolotrealanis98/open-apollo.git
cd open-apollo
sudo bash scripts/install-usb.sh

The installer handles dependencies, firmware setup, kernel module build, DSP initialization, and PipeWire configuration. You'll need the Apollo firmware file from UA's website — the installer will prompt you if it's missing.

After install, the following PipeWire devices are available:

Device	Type	Channels
Apollo Solo USB Mic 1	Source (capture)	Mono
Apollo Solo USB Mic 2	Source (capture)	Mono
Apollo Solo USB Mic 1+2	Source (capture)	Stereo
Apollo Solo USB Monitor	Sink (playback)	Stereo
Apollo Solo USB Headphone	Sink (playback)	Stereo

Start the Mixer Daemon

cd mixer-engine
python3 ua_mixer_daemon.py -v

The daemon exposes TCP:4710, TCP:4720, and WS:4721 for mixer control from any client application.

Architecture

┌──────────────┐   ┌──────────────┐
│ Control App  │   │ Control App  │
│ (TCP:4710)   │   │ (TCP:4720)   │
└──────┬───────┘   └──────┬───────┘
       │                  │
       └────────┬─────────┘
                │
       ┌────────▼────────┐
       │  Mixer Daemon   │
       │  (Python)       │
       └────────┬────────┘
                │ ioctl
       ┌────────▼────────┐
       │  Kernel Driver  │
       │  (ua_apollo.ko) │
       └────────┬────────┘
                │ MMIO
       ┌────────▼────────┐
       │  Apollo Hardware │
       │  (BAR0 regs)    │
       └─────────────────┘

Components

Component	Path	Description
Driver	`driver/`	Linux PCIe kernel module — DMA, ALSA, DSP ring buffer, preamp control
Mixer Daemon	`mixer-engine/`	TCP:4710 + TCP:4720 + WS:4721 daemon — state tree, hardware routing, metering
Configs	`configs/`	PipeWire, WirePlumber, and UCM2 configuration profiles
Tools	`tools/contribute/`	Device probe and capture scripts for community contributions

Documentation

Full documentation at open-apollo-docs.pages.dev, including:

Installation guide — build, install, configure
Supported devices — model compatibility table
Architecture overview — how the pieces fit together
Register map — BAR0 hardware register documentation
DSP protocol — ring buffer commands and settings batch protocol
How to contribute — testing, device captures, code contributions

Documentation content lives in the docs/ directory of this repo. Edit the Markdown files there and submit a PR — changes are automatically deployed to the docs site.

Contributing

We welcome contributions of all kinds — from device testing reports to driver code. See CONTRIBUTING.md for details.

The most impactful thing you can do right now is test on your hardware. If you own any Apollo model besides the x4, your testing report directly enables support for that device.

Quick contribution path

Build and load the driver
Run ./tools/contribute/device-probe.sh
Submit a device report

License

This project is licensed under the GNU General Public License v2.0.

See NOTICE.md for information about trademarks and intellectual property.

Name		Name	Last commit message	Last commit date
Latest commit History 154 Commits
.github		.github
configs		configs
console-web		console-web
devices		devices
docs		docs
driver		driver
mixer-engine		mixer-engine
nix		nix
scripts		scripts
tools		tools
.gitignore		.gitignore
ARCHITECTURE.md		ARCHITECTURE.md
CHANGELOG.md		CHANGELOG.md
CODE_OF_CONDUCT.md		CODE_OF_CONDUCT.md
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
NOTICE.md		NOTICE.md
README.md		README.md
SECURITY.md		SECURITY.md
flake.nix		flake.nix

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Repository files navigation

Open Apollo

What Works (Apollo x4 — Thunderbolt, Ubuntu 24.04)

What Works (Apollo Solo USB)

USB Known Issues

Known Issues

App Compatibility

Not Yet Implemented

Supported Devices

Thunderbolt Models

USB Models

Thunderbolt 2 Devices (Not Supported)

Quick Start

Prerequisites

Install

NixOS (Thunderbolt)

Uninstall

Troubleshooting

Virtual I/O devices (Apollo x4)

USB Quick Start (Apollo Solo USB)

Start the Mixer Daemon

Architecture

Components

Documentation

Contributing

Quick contribution path

License

About

Uh oh!

Releases 6

Packages

Uh oh!

Contributors

Uh oh!

Languages

Folders and files

Latest commit

History

Repository files navigation

Open Apollo

What Works (Apollo x4 — Thunderbolt, Ubuntu 24.04)

What Works (Apollo Solo USB)

USB Known Issues

Known Issues

App Compatibility

Not Yet Implemented

Supported Devices

Thunderbolt Models

USB Models

Thunderbolt 2 Devices (Not Supported)

Quick Start

Prerequisites

Install

NixOS (Thunderbolt)

Uninstall

Troubleshooting

Virtual I/O devices (Apollo x4)

USB Quick Start (Apollo Solo USB)

Start the Mixer Daemon

Architecture

Components

Documentation

Contributing

Quick contribution path

License

About

Topics

Resources

License

Code of conduct

Contributing

Security policy

Uh oh!

Stars

Watchers

Forks

Releases 6

Packages 0

Uh oh!

Contributors

Uh oh!

Languages

Packages