Supported Devices

Open Apollo supports Universal Audio Apollo Thunderbolt and USB interfaces. Thunderbolt models use a native Linux kernel driver. USB models use a pure-userspace stack (UAC 2.0 audio + patched snd-usb-audio — no kernel module required).

Thunderbolt devices

USB devices

USB Apollo models use UAC 2.0 audio. No kernel module is required — the FX3 firmware is uploaded from userspace on each power-on, and snd-usb-audio (with a 4-patch out-of-tree build) handles audio streaming. See USB RE findings for protocol details.

Column definitions

• Playback: Number of playback (output) channels at 48 kHz
• Record: Number of record (input) channels at 48 kHz
• Preamps: Number of analog preamp inputs with gain/48V/PAD controls
• HiZ: Number of preamp channels that support Hi-Z (instrument) input
• Status: Whether the model has been tested on Linux with this driver

What "Verified" means

Thunderbolt (Apollo x4)

The Apollo x4 is the primary development and test device. On this model, the following features are confirmed working:

• Full duplex audio with 4 analog inputs (Mic 1-4) and 6 analog outputs (Monitor L/R, Line Out 1-4) verified
• The driver exposes all 24 playback / 22 record ALSA channels, but S/PDIF, ADAT, and virtual (DAW playback) channels are unverified and likely not working
• All six sample rates (44.1, 48, 88.2, 96, 176.4, 192 kHz)
• Preamp gain control (all 4 channels)
• Preamp flags: 48V phantom power, PAD, low cut, phase invert, mic/line switching
• Monitor volume, mute, dim, mono, talkback
• DSP mixer routing (analog buses only — digital bus routing untested)
• ALSA integration with 50+ mixer controls

USB (Apollo Solo USB)

The Apollo Solo USB is fully verified on Ubuntu Studio 24.04 / Intel Tiger Lake-H (confirmed by contributor @stoneiboyz-sys). Full duplex is working with no daemon required:

• 6ch playback (S32_LE 48kHz) confirmed on Ubuntu Studio 24.04 (kernel 6.17, Intel) and CachyOS (kernel 6.19, AMD)
• 10ch capture — confirmed working on Ubuntu Studio 24.04; one-shot usb-full-init.py (38 packets, includes DSP program load) then modprobe snd_usb_audio
• PipeWire capture — mic input working; Discord voice calls and pw-record confirmed
• PipeWire playback — browser audio, system audio, DAWs working
• Hardware monitoring — mic → headphones simultaneous with active PipeWire streams
• Preamp gain, 48V, monitor level/mute — working via vendor control 0x03 (seq counter fix applied)
• No daemon required — EP6 drain daemon removed; one-shot init is stable

Known limitation: usb-full-init.py crashes at packet 28 on some firmware builds (IIR biquad SRAM address mismatch — observed on CachyOS/AMD with a different Cauldron build). Playback-only still works on those systems.

See USB RE findings for the full protocol details.

What "Needs Testing" means

These models are recognized by the driver and have correct channel count configurations, but have not been tested on actual hardware. They likely work — the Apollo product line shares a common architecture — but may need adjustments to routing tables or feature flags.

How to help

If you own an Apollo model marked "Needs Testing", your contribution would be extremely valuable. Even basic testing (does the driver load? does ALSA see the device? does audio play?) helps us mark models as verified.

See How to Contribute for details, or jump straight to the device capture guides:

• Device Capture (macOS) — capture routing data using DTrace

You can also run the quick probe script on Linux:

sudo ./tools/contribute/device-probe.sh

This reads basic device information and outputs a report you can submit.