Motu M4 Audio Interface Review

[JimmyBuckets]

It'll probably drain your battery pretty quickly, though.

Yeah if I had to guess it was loosing 1% about every minute or so. It's about the same as gaming on my phone. I figure I could get an hour of listening if I wanted in a pinch and still have 30-40% battery left.

 

[drake5000]

Thank you for the review and all helpful comments.
I already have Atom AMP and considering to get Motu M4 for pairing them up. According to specs, the “lowest” max output level of its DAC is +9.5 dBu (2.3 Vrms) via RCA. But I have couple high-sensitive headphones which my Atom drives a bit too loud even at standart 2.1 Vrms signal, so I sit basically at minimal levels of the volume knob. My question is, in case output signal of Motu m4 will be to loud for my personal use case, which is the “correct” way to lower it in terms of signal-to-noise and signal-to-distortion? I’m also concerned about entering that -30dBFS “IMD Hump” territory.
I see three options:
1. via playback software (I mainly use iTunes and Spotify)
2. via windows sound panel
3. via Motu M4 volume knob.
(4. via motu software panel probably?)

 

[JimmyBuckets]

Doesn't the atom have high and low gain?

 

[Hippocamp]

I have two usage scenarios planned for a Motu M4

1. M4 USB DAC --> balanced line out --> THX 789 headphone amp
2. M4 USB DAC --> balanced monitor out --> powered monitors

BUT, I also have a a turntable in the system, and I'm wondering if the I could use the M4 as a volume control interface between the turntable and the powered speakers. That is, could I route my Phono Amp into two of the input channels, put the M4 in Direct Monitoring mode, and then control the output level to the powered monitors for phono playback? As a newbie... It seems that this would do nothing more than put a volume pot in the chain between the phono amp and the powered monitors (right? or way off...?). Also, if this would work, would the cabling require anything more sophisticated than simple RCA (phono amp out) to TRS (M4 in) cables?

 

[sharpty]

Just noticed a new update for the M4 and M2 as of 3/26.

Windows changelog - Improved performance with low buffer size.

Mac changelog - Added macOS Big Sur support, Added Apple Silicon support.

BUT, I also have a a turntable in the system, and I'm wondering if the I could use the M4 as a volume control interface between the turntable and the powered speakers. That is, could I route my Phono Amp into two of the input channels, put the M4 in Direct Monitoring mode, and then control the output level to the powered monitors for phono playback? As a newbie... It seems that this would do nothing more than put a volume pot in the chain between the phono amp and the powered monitors (right? or way off...?). Also, if this would work, would the cabling require anything more sophisticated than simple RCA (phono amp out) to TRS (M4 in) cables?

Yes that will work. You just need to enable channel 3-4 monitoring and pan the mix knob to input.

For the cable you can use RCA to TS cables or RCA to TS adapters with standard RCA cable. Since RCA is unbalanced, there is no need for 3 conductors. Using a male TS will just short one side of the balanced input to ground.

EDIT again : If you hold the monitor button on the interface, it will switch from mono to stereo monitoring with the XLR inputs. I assume input 3-4 are stereo too, but I haven't tested it.

 

[Hippocamp]

[QUOTE="Yes that will work. You just need to enable channel 3-4 monitoring and pan the mix knob to input.

For the cable you can use RCA to TS cables or RCA to TS adapters with standard RCA cable. Since RCA is unbalanced, there is no need for 3 conductors. Using a male TS will just short one side of the balanced input to ground.

EDIT again : If you hold the monitor button on the interface, it will switch from mono to stereo monitoring with the XLR inputs. I assume input 3-4 are stereo too, but I haven't tested it.[/QUOTE]


Excellent, thanks. A one box solution!

 

[adg]

Do any Motu M2 or M4 owners have any experience pulling off any of the knobs on the front of the unit? I just received an M4 a few days ago that I'm using to replace a Schiit Modius and JDS Labs El Amp II, and I'm interested in putting on a smaller knob on the headphone volume pot on the way right of the unit. I'd like to make it easier to grab the monitor volume knob without having my thumb getting forced between the monitor and headphone volume knobs. I tried to pull on the knob with a medium amount of force and it wasn't coming off. I don't see a hex screw holding it in place, so maybe the knob is just on tightly and can be pulled off, but I didn't want to break anything.

I know this is an odd question, but this is the first place I thought to ask it. There's an active thread on Gearspace which I can go to next (I'm not registered there). I'm kind of obsessive when it comes to having an awesome volume control knob/experience, and this gritty headphone volume knob is just a bit too close for me. My thumbnail gets pushed up against it every time I go to grab the monitor knob with my left hand. Making it stick out less or getting a less wide knob would help. I'm using the RCA line outs of the unit to go to my Bottlehead Crack, so I won't use the headphone out that often. I won't leave the potentiometer shaft naked, but would be happy to find an even tinier knob to put on it.

Other than this weird issue, I'm enjoying the M4 so far. In a future Motu model, I think it would be cool to have a bit more spacing between the monitor and headphone volume knobs, and also maybe put on an OLED screen instead of what I believe is an LCD. An OLED screen with better blacks would look great with the pure black casing, and the VU meter would pop more and look better in the dark. Moving one or both XLR inputs to the back would also be nice (to me).

 

[txbdan]

Do any Motu M2 or M4 owners have any experience pulling off any of the knobs on the front of the unit? I just received an M4 a few days ago that I'm using to replace a Schiit Modius and JDS Labs El Amp II, and I'm interested in putting on a smaller knob on the headphone volume pot on the way right of the unit. I'd like to make it easier to grab the monitor volume knob without having my thumb getting forced between the monitor and headphone volume knobs. I tried to pull on the knob with a medium amount of force and it wasn't coming off. I don't see a hex screw holding it in place, so maybe the knob is just on tightly and can be pulled off, but I didn't want to break anything.

I know this is an odd question, but this is the first place I thought to ask it. There's an active thread on Gearspace which I can go to next (I'm not registered there). I'm kind of obsessive when it comes to having an awesome volume control knob/experience, and this gritty headphone volume knob is just a bit too close for me. My thumbnail gets pushed up against it every time I go to grab the monitor knob with my left hand. Making it stick out less or getting a less wide knob would help. I'm using the RCA line outs of the unit to go to my Bottlehead Crack, so I won't use the headphone out that often. I won't leave the potentiometer shaft naked, but would be happy to find an even tinier knob to put on it.

Other than this weird issue, I'm enjoying the M4 so far. In a future Motu model, I think it would be cool to have a bit more spacing between the monitor and headphone volume knobs, and also maybe put on an OLED screen instead of what I believe is an LCD. An OLED screen with better blacks would look great with the pure black casing, and the VU meter would pop more and look better in the dark. Moving one or both XLR inputs to the back would also be nice (to me).

Email MOTU. They normally respond same day and are normally very helpful.

 

[adg]

Email MOTU. They normally respond same day and are normally very helpful.

Thanks for the suggestion. I just sent an email and will report back with what I'm told.

 

[sharpty]

Do any Motu M2 or M4 owners have any experience pulling off any of the knobs on the front of the unit? I just received an M4 a few days ago that I'm using to replace a Schiit Modius and JDS Labs El Amp II, and I'm interested in putting on a smaller knob on the headphone volume pot on the way right of the unit. I'd like to make it easier to grab the monitor volume knob without having my thumb getting forced between the monitor and headphone volume knobs. I tried to pull on the knob with a medium amount of force and it wasn't coming off. I don't see a hex screw holding it in place, so maybe the knob is just on tightly and can be pulled off, but I didn't want to break anything.

I know this is an odd question, but this is the first place I thought to ask it. There's an active thread on Gearspace which I can go to next (I'm not registered there). I'm kind of obsessive when it comes to having an awesome volume control knob/experience, and this gritty headphone volume knob is just a bit too close for me. My thumbnail gets pushed up against it every time I go to grab the monitor knob with my left hand. Making it stick out less or getting a less wide knob would help. I'm using the RCA line outs of the unit to go to my Bottlehead Crack, so I won't use the headphone out that often. I won't leave the potentiometer shaft naked, but would be happy to find an even tinier knob to put on it.

Other than this weird issue, I'm enjoying the M4 so far. In a future Motu model, I think it would be cool to have a bit more spacing between the monitor and headphone volume knobs, and also maybe put on an OLED screen instead of what I believe is an LCD. An OLED screen with better blacks would look great with the pure black casing, and the VU meter would pop more and look better in the dark. Moving one or both XLR inputs to the back would also be nice (to me).

I just tried to pull them off but they're stuck pretty well. I'm certain they are just press-on knobs, but I'm not going to pull any harder to remove them. I also think you'll have trouble finding a slimmer knob.

You can adjust the knobs with one finger by rolling them.

 

[adg]

Motu support said the knob should pull off. I didn’t have success using my fingers, but using a small flathead screwdriver as a lever and putting a thick paper towel to protect the case made the job easy.

The pot shaft diameter is pretty big in comparison to the knob, but I’m going to try making as small of a knob as possible using some Sugru. Will post some pics when I’m done.

 

[lizhuoyin]

Plan to buy one. Mainly connect one set of balanced outputs to a pair of active monitors along with headphone for playing music from Windows.
I want to listen to music either from speakers or headphone, but not both.
My questions are:
1. Does the main volume control control both balanced line out and monitor out? I guess you can select audio output in windows to 1/2 or 3/4, right?
2. I understand headphone outputs share signals from output 1/2. Does that mean I have to connect active speakers to 3/4 if I only want to listen from headphone? If that's the case, is 3/4 line outs' volume controlled by main volume knob?

 

[sharpty]

Plan to buy one. Mainly connect one set of balanced outputs to a pair of active monitors along with headphone for playing music from Windows.
I want to listen to music either from speakers or headphone, but not both.
My questions are:
1. Does the main volume control control both balanced line out and monitor out? I guess you can select audio output in windows to 1/2 or 3/4, right?
2. I understand headphone outputs share signals from output 1/2. Does that mean I have to connect active speakers to 3/4 if I only want to listen from headphone? If that's the case, is 3/4 line outs' volume controlled by main volume knob?

Outputs 1-2 (monitor out) are controlled by the main knob. Out 3-4 volume can only be controlled in the OS. You can switch between 1-2 and 3-4 in windows.

Connect your speakers to 1-2 so you can control them with the main knob, and if you want to use the integrated headphone amp only, turn down the main knob and turn up the headphone knob.

If you want to use an external headphone amp, connect it to 3-4 and control the volume using the amp. You'll probably want to lower the 3-4 output level in windows to keep from over-driving the amp though.

 

[umbral]

Same question for M4 as for M2 :
https://www.audiosciencereview.com/...view-audio-interface.19911/page-8#post-743109

Thank you.

 

[somebodyelse]

Same question for M4 as for M2 :
https://www.audiosciencereview.com/...view-audio-interface.19911/page-8#post-743109

Thank you.

The headphone amp in the M2 and M4 measures similarly so the answers will apply equally to both. Solderdude's downloads page includes some relevant tutorials covering power output, headphone impedance and sensitivity, and how much output you need with different headphones to hit volume levels. If the MOTU headphone output doesn't have enough power for your DT-770s you can get some more efficient headphones, or use a more powerful headphone amp connected to the line or headphone output - the line output measured a bit better, but it might not be practical to use depending on what else you want to connect. Check the master review index for headphone amps - the L30, Atom and Heresy spring to mind. Amirm's headphone reviews include a chart showing sensitivity of headphones tested in mV, although it's quite a short list at the moment. The AKG K371 might be sensitive enough to hit the volume you want with the MOTU while performing well, but do read the review.

 

[txbdan]

To close the loop on some questions I had and were floating around, I connected my second PC to my M4 yesterday. My primary PC is of course connected via USB and the TRS monitor outs go to monitors. For my second PC, I used a TS/3.5mm splitter and a 3.5mm cable to connect the audio out on the computer to inputs 3/4 on the M4. I simply press the monitor "3-4" button and the second PC plays as expected on the monitor outputs and is controlled by the volume knob. When I'm not using the second PC audio I can push off the "3-4" button to disable those inputs to ensure no noise is getting into my primary system. Easy peasy.

 

[umbral]

The headphone amp in the M2 and M4 measures similarly so the answers will apply equally to both. Solderdude's downloads page includes some relevant tutorials covering power output, headphone impedance and sensitivity, and how much output you need with different headphones to hit volume levels. If the MOTU headphone output doesn't have enough power for your DT-770s you can get some more efficient headphones, or use a more powerful headphone amp connected to the line or headphone output - the line output measured a bit better, but it might not be practical to use depending on what else you want to connect. Check the master review index for headphone amps - the L30, Atom and Heresy spring to mind. Amirm's headphone reviews include a chart showing sensitivity of headphones tested in mV, although it's quite a short list at the moment. The AKG K371 might be sensitive enough to hit the volume you want with the MOTU while performing well, but do read the review.

Thank you very much. Very good information.
I replied here on M2 : https://www.audiosciencereview.com/...view-audio-interface.19911/page-8#post-744314

 

[umbral]

Motu 4 ADC results being better than Motu 2 ADC (104 dB vs 96 dB) is simply because other conections in the back on the M4 were used for connecting instead of the front ones on the M2, yes ?

But microphones can't be connected to M4 back yes ? So between M2 & M4 for microphone usage there would be no difference ?

Are my assumptions corect ?

 

[617]

Motu 4 ADC results being better than Motu 2 ADC (104 dB vs 96 dB) is simply because other conections in the back on the M4 were used for connecting instead of the front ones on the M2, yes ?

But microphones can't be connected to M4 back yes ? So between M2 & M4 for microphone usage there would be no difference ?

Are my assumptions corect ?

In recording, the ADC is not the limiting factor in audio input quality as much as the noise performance of the microphone inputs, which Amir did not characterize. However, I can tell you from experience that the noise performance of the m4 is good enough to record with insensitive dynamic microphones easily, if that is your concern. Think about it, the ADC test uses an ultra clean, low distortion, low noise signal, and then digitizes it. What recording sources do you have that can perform at that level of noise and distortion? Mics have self noise, musical instruments have all kinds of noise and distortion, etc. I wouldn't get hung up on ADC quality.

I have used a few inexpensive wired and portable interfaces for recording at quiet levels with insensitive mics, and the m4 is the best of them.

 

[sharpty]

Motu 4 ADC results being better than Motu 2 ADC (104 dB vs 96 dB) is simply because other conections in the back on the M4 were used for connecting instead of the front ones on the M2, yes ?

But microphones can't be connected to M4 back yes ? So between M2 & M4 for microphone usage there would be no difference ?

Are my assumptions corect ?

Yes, the M4 rear line inputs bypass the preamp, that's why they're cleaner.

You can't connect a mic directly to the rear line inputs. If you have a dedicated mic preamp / channel strip, then you could use the rear input for mics.

Otherwise the front mic inputs should be the same.