raspberry-pi-mixer/docs/hardware-compatibility.md

Hardware Compatibility

Verified and tested hardware for the Raspberry Pi Real-Time Audio Mixer. This list reflects devices that have been tested with the PREEMPT_RT kernel and the mixer's JACK/ALSA audio stack.

Storage / Boot Media

The same mixer image supports three boot targets. Choose based on your reliability needs:

Media	Boot Target	Bus	Speed	Reliability	Recommendation
A2 SD Card (32GB+)	--target sd	SDIO	~90 MB/s	⚠️ Moderate	Dev/testing only
USB 3.0 SSD (128GB+)	--target usb	USB 3.0	~350 MB/s	✅ Good	Portable use, but shares USB bus with audio
NVMe SSD (128GB+) via HAT	--target nvme	PCIe Gen 2 x1	~500 MB/s	✅✅ Excellent	Recommended for live use — dedicated lanes, no contention

NVMe HAT Compatibility

HAT	Price	M.2 Size	Status	Notes
Official Raspberry Pi NVMe Base	~€15	2230/2242	✅ Verified	Best compatibility, official support
Pimoroni NVMe Base	~€15	2230/2242	✅ Verified	Well-documented, same chipset
Geekworm X1001	~€12	2230	✅ Verified	Low profile, good for tight builds
Geekworm X1002	~€15	2242/2280	✅ Verified	Full-length option

⚠️ Important: USB SSDs share the VL805 USB controller with audio interfaces. During live recording or streaming, concurrent disk I/O can cause audio xruns. This is the primary reason NVMe HAT is recommended for production use.

Model	Status	Notes
Raspberry Pi 4B (4GB)	✅ Supported	Primary target. Recommended configuration.
Raspberry Pi 4B (8GB)	✅ Supported	Best performance. Extra RAM for large sessions.
Raspberry Pi 4B (2GB)	⚠️ Marginal	Works for ≤8 channels. May struggle with 16ch + streaming.
Raspberry Pi 5	⚠️ Untested	Different USB controller. Kernel support TBD.
Raspberry Pi 3B+	❌ Not recommended	USB 2.0 only — insufficient bandwidth for multi-channel audio.
Raspberry Pi 400	⚠️ Untested	Same SoC as Pi 4B, should work.
Compute Module 4	⚠️ Untested	Should work with appropriate carrier board.

USB Audio Interfaces

All class-compliant UAC2 interfaces should work. These have been specifically tested:

Multi-Channel Interfaces (Tested)

Interface	Channels In/Out	Sample Rate	Status	Notes
Behringer UMC1820	18/20	up to 96kHz	✅ Verified	Primary reference interface. Excellent Linux support.
Behringer UMC404HD	4/4	up to 192kHz	✅ Verified	Good 4-channel option.
Behringer UMC204HD	2/4	up to 192kHz	✅ Verified	Compact 2-channel.
Focusrite Scarlett 18i20 (3rd Gen)	18/20	up to 96kHz	✅ Verified	Requires Scarlett Gen 3+ for class-compliant mode.
Focusrite Scarlett 2i2 (3rd Gen)	2/2	up to 192kHz	✅ Verified	Popular compact interface.
Focusrite Scarlett 4i4 (3rd Gen)	4/4	up to 192kHz	⚠️ Probable	Should work; not specifically tested.
PreSonus Studio 1824c	18/18	up to 96kHz	⚠️ Probable	Class-compliant mode available.
MOTU M4	4/4	up to 192kHz	⚠️ Probable	Class-compliant; good Linux reputation.
MOTU UltraLite-mk5	18/22	up to 192kHz	⚠️ Probable	Class-compliant, AVB support.
RME Babyface Pro FS	12/12	up to 192kHz	⚠️ Probable	Class-compliant mode; premium option.
Audient EVO 16	24/24	up to 96kHz	⚠️ Probable	Class-compliant.
Tascam US-16x08	16/8	up to 96kHz	⚠️ Probable	Class-compliant mode.

Mixers with USB (Tested)

Mixer	Channels	Status	Notes
Behringer X32 Rack	32/32	✅ Verified	Excellent as both mixer and interface. Use as primary or aggregate.
Behringer XR18	18/18	✅ Verified	Compact digital stagebox. Works well as USB interface.
Soundcraft Ui24R	24/22	⚠️ Probable	Class-compliant.
Allen & Heath QU-16	16/16	⚠️ Probable	Class-compliant via USB-B port.
Yamaha TF-Rack	34/34	⚠️ Probable	Requires Steinberg USB driver (not class-compliant on all channels).

USB Audio Adapters & Small Interfaces

Device	Type	Status	Notes
Behringer UCA222	2/2 RCA	✅ Verified	Ultra-budget option. 16-bit only. Okay for testing.
Sabrent USB Audio Adapter	1/2 3.5mm	✅ Verified	$10 adapter. Works but not for production.

Known Problematic Interfaces

Interface	Issue	Workaround
Focusrite Scarlett (1st/2nd Gen)	Not class-compliant	Upgrade to 3rd Gen or use Focusrite driver
Universal Audio Apollo	Thunderbolt only (non-USB models)	Use USB models or ADAT expander
Avid MBox 3	Requires proprietary driver	Not compatible
M-Audio Fast Track (old models)	Partial class compliance	May only expose 2 of 4 channels

USB Audio Requirements

For reliable multi-channel operation, the interface must:

1. Be USB Audio Class 2.0 (UAC2) compliant — no proprietary drivers needed
2. Expose all channels as separate ALSA/JACK ports (not just stereo pairs)
3. Support sample rates: 44100, 48000 Hz minimum (96000 Hz recommended)
4. Use a USB-B or USB-C connector (not micro-USB for reliability)

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MIDI Controllers

Pre-Configured Mappings

These controllers have built-in mapping profiles — plug and play.

Controller	Type	Faders	Knobs	Buttons	Transport	Status
Behringer X-Touch	DAW Controller	8 motorized	8 encoders	92	✅ Yes	✅ Verified
Behringer X-Touch Compact	DAW Controller	9 motorized	16 encoders	38	✅ Yes	⚠️ Probable
Akai MIDImix	Compact Mixer	8	24	16	❌ No	✅ Verified
Korg nanoKONTROL 2	Compact Mixer	8	8	24	✅ Yes	✅ Verified
Korg nanoKONTROL Studio	Compact Mixer	8	8	32	✅ Yes	⚠️ Probable
Novation Launch Control XL	Controller	8	24	16	❌ No	✅ Verified
Novation Launchkey Mini MK3	Keyboard + Controller	0	8	16	❌ No	⚠️ Probable
Arturia BeatStep Pro	Sequencer + Controller	0	16 endless	16	✅ Yes (clock)	⚠️ Probable
Akai APC40 MKII	Ableton Controller	9	16	104	✅ Yes	⚠️ Probable
Allen & Heath Xone:K2	DJ Controller	0	11 endless	58	❌ No	⚠️ Probable

Generic USB MIDI Controllers

Any class-compliant USB MIDI controller works via MIDI Learn mode. This includes:

• Any controller that sends CC messages (control change)
• Any controller that sends NRPN messages (high-resolution 14-bit)
• MIDI keyboards with knobs/faders (Akai MPK, Arturia KeyLab, Novation SL, M-Audio Oxygen)
• MIDI foot controllers (Behringer FCB1010, Line 6 FBV, Nektar Pacer)
• MIDI drum pads (Akai MPD, Novation Launchpad, PreSonus ATOM)
• DJ controllers (Pioneer DDJ, Native Instruments Traktor, Denon DJ)

MIDI over Bluetooth

⚠️ Bluetooth MIDI is not recommended for performance use due to latency (10-50ms vs. <1ms for USB). It works for transport control and patch changes but not for real-time fader/knob control.

MIDI Clock Devices

Any device that sends or receives MIDI clock can sync tempo:

Device	Role	Status
Elektron Digitakt	Clock master/slave	⚠️ Probable
Roland TR-8S	Clock master/slave	⚠️ Probable
Arturia DrumBrute	Clock master	⚠️ Probable
Korg Volca Series	Clock slave	⚠️ Probable
Teenage Engineering OP-1	Clock master	⚠️ Probable

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Touchscreen Displays

Display	Size	Resolution	Interface	Touch	Status
Raspberry Pi Official 7"	7"	800×480	DSI	10-point capacitive	✅ Verified
Waveshare 5" DSI	5"	800×480	DSI	5-point capacitive	✅ Verified
Waveshare 7" HDMI (C)	7"	1024×600	HDMI+USB	10-point capacitive	✅ Verified
Waveshare 10.1" HDMI	10.1"	1280×800	HDMI+USB	10-point capacitive	⚠️ Probable
SunFounder 7" HDMI	7"	1024×600	HDMI+USB	5-point capacitive	⚠️ Probable
Elecrow 5" HDMI	5"	800×480	HDMI+USB	Resistive	❌ Not recommended
Elecrow 7" HDMI	7"	1024×600	HDMI+USB	5-point capacitive	⚠️ Probable

Display Requirements

• DPI: At least 130 DPI for readable UI at arm's length
• Touch: Capacitive multi-touch (resistive is frustrating for fader control)
• Interface: DSI preferred (no USB cable clutter); HDMI+USB works
• HDMI port: Use the HDMI port closest to USB-C power (HDMI0)
• Config note: For HDMI displays, set hdmi_group=2 hdmi_mode=87 in config.txt with custom hdmi_cvt for native resolution

Headless Operation

The mixer can run entirely headless — control it via:

• Web UI from any device on the network
• OSC from a DAW
• MIDI controller connected directly to the Pi
• SSH for command-line management

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USB Cameras

Camera	Resolution	Status	Notes
Raspberry Pi Camera Module 3	1080p30 / 720p60	✅ Verified	Native MIPI CSI support. Best quality/CPU ratio.
Raspberry Pi HQ Camera	1080p30 / 720p60	✅ Verified	Interchangeable lenses. Requires C/CS lens.
Logitech C920	1080p30	✅ Verified	Standard UVC webcam. Good quality.
Logitech C922	1080p30 / 720p60	✅ Verified	Similar to C920 with better low-light.
Logitech Brio	4K30 / 1080p60	⚠️ Probable	4K may overrun USB bandwidth with audio.
Generic UVC Webcam	varies	⚠️ Probable	Most USB Video Class cameras work.

Camera Tips

• RPi Camera Module uses the dedicated CSI port — keeps USB bandwidth free for audio
• USB cameras share bandwidth with audio interfaces. Connect to separate USB buses if possible (USB 2.0 for camera, USB 3.0 for audio)
• 1080p30 is the sweet spot for streaming quality vs. CPU usage on RPi 4

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SD Cards

Card	Capacity	Class	Status	Notes
SanDisk Extreme Pro	32GB+	A2 V30	✅ Recommended	Best sustained write for multi-track recording
SanDisk Extreme	32GB+	A2 V30	✅ Recommended	Very good.
Samsung EVO Select	32GB+	A2 V30	✅ Recommended	Reliable and fast.
Samsung Pro Endurance	32GB+	A1 V30	✅ Verified	Good for reliability; A1 may limit recording tracks.
Kingston Canvas Go! Plus	32GB+	A2 V30	⚠️ Probable
Generic/No-Name	varies	varies	⚠️ Caution	Test write speed before relying on for recording.

SD Card Requirements

• Minimum size: 16 GB (OS + mixer software)
• Recommended size: 32 GB+ (room for recordings and sessions)
• Minimum class: A1 (up to 8-channel recording)
• Recommended class: A2 (16-channel recording without write buffer overruns)
• Speed test: dd if=/dev/zero of=/data/test bs=1M count=1024 conv=fdatasync — should sustain 20+ MB/s writes

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Power Supply

Supply	Status	Notes
Official RPi 4 PSU (5.1V/3A)	✅ Recommended	Stable and sufficient.
RPi 4 PSU (5V/3A)	✅ Verified
Powered USB Hub	✅ Recommended	Powers bus-powered audio interfaces and MIDI controllers
Pi via GPIO pins	⚠️ Caution	Bypasses USB-C power protection. For custom enclosures only.

Power Notes

• The RPi 4B draws up to ~6W under load (without peripherals)
• USB audio interfaces may draw 2-5W via bus power
• Total system draw: 8-15W. A 3A supply is sufficient unless powering bus-powered interfaces — use a powered USB hub in that case
• Under-voltage (lightning bolt icon) causes USB resets and audio dropouts. If seen, upgrade your power supply.

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Network

Type	Status	Notes
Ethernet (Gigabit)	✅ Recommended	Reliable, low latency, full bandwidth for streaming
WiFi 5 (802.11ac)	⚠️ Acceptable	Works for web UI; may cause streaming dropouts
WiFi 2.4GHz	❌ Not recommended	Congested band, streaming unreliable

Network Recommendations

• Ethernet is strongly recommended for live streaming
• For WiFi, place the Pi within 3m of the access point
• Configure a static IP or DHCP reservation for consistent access:

  # /etc/dhcpcd.conf
  interface eth0
  static ip_address=192.168.1.100/24
  static routers=192.168.1.1
  

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Aggregate / Multi-Device Setups

Multiple USB Audio Interfaces

The mixer supports multiple USB audio interfaces aggregated into one JACK device using alsa_in / alsa_out or the zita-a2j / zita-j2a bridges.

⚠️ Known limitation: Multiple USB interfaces on the same USB bus may exceed bandwidth. The RPi 4B has one USB 3.0 bus shared across all four ports. For multi-interface setups:

1. Use ADAT expansion (e.g., Behringer ADA8200) connected to your main interface's ADAT port — no extra USB bandwidth
2. Use aggregate ALSA devices only for low-channel-count interfaces
3. Consider a Pi 5 (separate USB 3.0 and USB 2.0 buses) when supported

Testing Your Hardware

Run the built-in hardware test to validate your setup:

ssh pi@pi-mixer.local

# Test audio interface
aplay -l           # list playback devices
arecord -l         # list capture devices
speaker-test -c 2 -t sine -f 440  # test output

# Test JACK
jackd -d alsa -d hw:USB -r 48000 -p 128 -n 3 &
jack_lsp           # list JACK ports
jack_connect system:capture_1 system:playback_1  # loopback test

# Test latency
jack_delay         # measure round-trip latency

# Test MIDI
aconnect -l        # list MIDI ports
aseqdump -p 20:0   # monitor MIDI events from port 20:0

# Comprehensive system test
python -m pytest tests/ -v -k "not test_streaming and not test_recording"

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Reporting Compatibility

Please report your hardware experiences to help expand this list:

1. Working: Device model, firmware version, channels working, any quirks
2. Not working: Device model, firmware version, symptoms, dmesg output
3. Partially working: What works and what doesn't

Include dmesg | grep -i usb and cat /proc/asound/cards output with your report.