MOTU decided to get into the budget market and I’m really curious to see what they can deliver in the $200 price range. Let’s plug it in and see if it knows how to Linux.
Drivers
The MOTU M4 is class compliant so no additional drivers are needed. You will need kernel 5.14 or later to prevent audio glitches.
Pulseaudio
The MOTU M4 will function like any other sound device in pavucontrol.
Jack
Select the ALSA driver to connect your MOTU M4 to the Jack server.
Round-trip Latency
While many kinds of audio latency metrics exist, one useful and well-understood metric is round-trip latency; the time it takes for an audio signal to enter the input of a device, get processed, and exit the output.
Kernel 5.16 brings improvements for low-latency USB audio on Linux and the M4 appears to take advantage of it.
If jack_iodelay is to be believed round-trip latency at 96000Hz/32 went from 3.14ms to 1.74ms. I’m a little suspicious since MOTU reports 2.5ms with the same settings.
Outside of that, the latency measurements line up with what I’ve seen reported by other M4 owners on Windows & MAC.
Testing setup
| CPU | AMD Ryzen 7 1700 |
| RAM | Corsair Vengeance LPX 16GB |
| Motherboard | MSI B350 Tomahawk |
| GPU | Nvidia NVS 300 |
| SSD | Samsung 840 |
| PSU: | EVGA 600 B1 |
| Firewire: | Syba SY-PEX30016 |
| Network: | Intel i350-T4 |
| OS: | Debian Bullseye |
| Kernel: | 5.16 low-latency |
| Desktop: | NA |
Verdict
The MOTU M4 was made to compete against the Focusrite Scarlett 4i4 and they nailed it. MOTU even tossed in a power switch, blinky meters, and individual buttons for phantom power and monitoring.
There are no drivers to install but you will need kernel 5.14+ unless you enjoy random audio glitches.
AD/DA conversion is fine for the price. Nothing earth shattering but absolutely nothing to complain about.
While the meters are fun to look at, they’re a gimmick. You’re not setting accurate input levels with them and they’re always on.
Also, no options for rack mounting? You do that for your ultralight series interfaces, MOTU. Boo!
At the end of the day I like the M4. It’s well built, sounds the business, and packs a solid punch for the price. It’s not going to replace my 828MK3 but an Ultralite MK5 just might, if I can ever find one.
MOTU M4
MOTU M4 Desktop 4×4 USB Type-C Audio/MIDI Interface.
Pros
Two 60dB preamps.
Two line level inputs.
MIDI
Power switch.
Cons
Unnumbered volume meters.
No option for rack mounting.
