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Product Review: MOTU M2 USB AMP/DAC Audio Interface

MOTU M2 AMP/DAC

The MOTU M2 audio interface is a USB bus powered AMP/DAC with electronics and features typically not found in its price range. I paid U.S. $199 for it in early 2022 and it looks like the price remains unchanged.

Notable features of the M2 include a physical on/off switch, a button to enable/disable phantom power for your microphone, a button to enable/disable microphone loopback, and stereo LCD input and output level meters, though they lack a text db scale.

The MOTU M2, made by the U.S. based company MOTU, has garnered tons of positive reviews, however it's not perfect in my opinion. My comments will not be from the perspective of an audiophile since i don't consider myself to be a member of that elusive club. Instead i'll cover some of the basics and my impressions and experience with using it on a GNU/Linux OS. If you want the impressions of an extremely knowledgeable, unbiased, hyper-geek audiophile, i'd suggest turning to Julian Krause, though the video thumbnail pretty much says it all.

Audio hardware on a Linux desktop OS seems to be a bit of a hit or miss affair and the MOTU M2 is no exception. Part of the problem seems to be the audio subsystem software. PulseAudio, which made its appearance in 2004, is still the prevalent audio processor in many Linux desktop distributions, however it has always had its shortcomings and apparently it isn't a favorite of musicians. The new kid on the block, PipeWire, aims to replace and greatly improve upon PulseAudio and though it works better than its predecessor in some respects, at version 0.3 as of this writing, it has a lot of ground to cover before it goes mainstream, though there are a couple distros as of this writing that include it by default.

In my case i use Manjaro Linux ('Arch for dummies' as i affectionately call it) on a scratch-built desktop PC along with PipeWire, the WirePlumber session manager and EasyEffects. My microphone is a Senal MC24-ES shotgun. For monitors i use the PreSonus Eris speakers and for headphones, it's the HIFIMAN Sundara planar magnetic. Given what i've learned about audio, i guess i would classify my setup as something around the 'advanced novice' or 'budding audiophile' level, though i'm not really a member of the latter since i think my flower has bloomed about as colorful as i care to get.

Regarding audio hardware, it seems to me that you can spend a little and get a little, or spend a moderate amount and get 'good', but exceeding 'good' requires an expenditure on a scale that is completely disproportionate to the minor step-up in quality achieved.

For music, it's strictly lossless for me and i prefer the FLAC format. Having worked long and hard on a Bash music processing script for Linux, and learning a lot about the different formats in the process, i am soooo very done with MP3's! Good bye. Good riddance. You always sucked!

Back to the task at hand, i don't have a lot to add to Julian's review. I think the reputation of the MOTU M2 is very well deserved. The build quality is very good, the knobs are silky smooth and don't produce any static when adjusted (they're digital), the feature set is pretty darn good and the sound quality and quality of the electronics exceeds that of many/most/all audio interfaces in its price range and outperforms that of some more expensive models from other manufacturers. As i mentioned earlier however, it's not perfect.

My gripes with the M2 are few and minor, and by no means are they a reason to avoid it. On my list are the following:

  • Switching between outputs requires lowering the volume on one and increasing it on the other. It would have been nice to have a switch instead.
  • No db scale on the LED meters, but the screen is colored so it's hardly a problem. More importantly, the M2 actually has meters which is unusual at this price point.
  • Contrary to Julian's comment regarding the amp, i feel like it's a little weak since the unit is powered only by USB and since the power output on the USB bus seems to vary among devices, i wonder if this may be problematic for some folks. On the plus side however, no separate power supply is needed.
  • Rather than disabling my mic in the OS when i'm not using it, i use the phantom power button on the M2, however it's located just below, and very close to, the mic gain knob which means it's easy to unintentionally change the gain when hitting the button. Disclaimer: This is probably one of the cheesiest, most inconsequential "gripes" ever, but i'm trying to list 5, so there.
  • None of the controls are backlit, the exception being when the monitor or phantom power buttons are engaged. Obviously this is a CATASTROPHIC design failure of EPIC proportions which has never before been realized! Or not.

One reason why i bought the M2 is because i wanted to lower the noise floor of my microphone and i'm pretty happy in that regard. Another was to replace the two prior amps i had, the Schiit Hel 2 and the Mayflower ARC MK2, both of which have an 1/8" mic jack and are oriented toward gamers. If by chance you're in the market for a "gaming" headphone amp (an amp with a mic input jack), i'd highly suggest avoiding both the Mayflower ARC and the Schiit Hel (my review is here) since they both have issues and, more importantly, at the same price point as the the MOTU M2, both pale in comparison with regard to features, connectivity, build quality and sound quality. That said, if you're dead set on a so-called "gaming" headphone amp (which offers exactly nothing over the MOTU M2), the Hel may be the better, over-priced option.

Now, more on the Linux part of all this...

Linux desktops represent a plethora of non-trivial problems as i hinted at earlier with the PulseAudio-PipeWire issue. Between unethical hardware manufacturers failing to support open-source software, the sound processing software problems and the often anemic drivers in the Linux kernel, the potential for headaches looms and so is the case with audio hardware on Linux from what i'm seeing. Who's to blame with regard to the MOTU M2 specifically, i can't really say beyond the problems with PulseAudio and PipeWire. If you're lucky, and i think chance are good you will be, you'll plug in the M2 and it will just work since it does not require any special driver and isn't built for any specific OS. If luck eludes you however, troubleshooting will ensue. The good news is that there are solutions for many/most problems regarding hardware compatibility issues of any kind on Linux and, regarding sound hardware specifically, the Arch wiki is a good place to start regardless of what flavor of Linux you're using.

In my case (Manjaro) the M2 just worked... and then one day, due to a package upgrade, it didn't. While the solution was a most simple one, discovering it consumed about 2 days of my time. If you have trouble, here's some commands that may be helpful for diagnosing the problem yourself or preparing to ask for help on the web. Some of these are OS specific and some are PipeWire specific:

$ hwinfo --sound
$ pactl info
$ pactl list sinks
$ alsa-info.sh --help
$ aplay -l
$ pw-top
$ journalctl --user-unit pipewire-pulse.service
$ journalctl -xe | grep pipewire
$ journalctl -f

PS: If you're thinking Windows is a better solution than Linux, you may want to read this and this and this and this for starters.

I suppose some sort of an obligatory conclusion is in order in the interest of providing a graceful exit to this somewhat unorthodox review, so with that in mind...

Buy it.

If you're in the market for a reasonably priced, high quality headphone/speaker amp with mic inputs and plenty of additional connectivity that performs exceedingly well given its price, outperforming some other higher priced units, the MOTU M2 is hard to beat at this time. As mentioned, it is a no-brainer compared to the Schiit Hel 2, the Mayflower ARC MK2, or any other "gaming" headphone/speaker amp i researched and the price is the same as the inferior Hel and ARC. There's a reason why so many peeps like this unit and it's a well justified one in my considered opinion.

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