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MOTU M6 Audio Interface Review

Rate this audio interface:

  • 1. Poor (headless panther)

    Votes: 5 3.5%
  • 2. Not terrible (postman panther)

    Votes: 47 33.3%
  • 3. Fine (happy panther)

    Votes: 82 58.2%
  • 4. Great (golfing panther)

    Votes: 7 5.0%

  • Total voters
    141

amirm

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This is a review and detailed measurements of the MOTU M6 professional audio interface. It is on kind loan from a member and costs US $400 as of this writing.

Motu M6 USB Audio Interface Professional Monitor Out DAC ADC Headphone Amplifier Review.jpg

The layout is clean as you see although that comes at the cost of not having input selection type (that is decided based on cable connection type -- see below). The LED have a grainy look to them but otherwise, nicely indicate clipping. Interesting to see dual headphone out, implying good drive capability. We will test this.

Power is provided through a 15 volt, 0.5 amp adapter (NOT USB):
Motu M6 USB Audio Interface Professional Monitor Out DAC ADC Headphone Amplifier back panel mi...jpg




Connector typeDynamic range (A-weighted)THD+N (unweighted)Max level
Line Output1/4" TRS, balanced, tip hot120 dB-110 dB+16 dBu
Line Input1/4" TRS, bal/unbal, tip hot115 dB-107 dB+18 dBu
Mic inputXLR, balanced, pin 2 hot115 dB-129 dBu EIN+10 dBu (at minimum gain)
Phones1/4", TRS stereo115 dB-110 dB+12.5 dBu

It is unclear whether the achieved DNR and THD+N are at the max levels indicated or some other.

MOTU M6 DAC Measurements
Two outputs are provided: Line Out and Monitor Out. Later is impacted based on volume position. Performance was the same in both so I stayed with Monitor Out so I could adjust the levels as needed:

Motu M6 USB Audio Interface Professional Monitor Out DAC Measurements.png

I read the spec as distortion and noise being down 110 dB which my measurements show to be conservative. As is, performance is very good for an interface:

Best audio interface review professional DAC 2025.png


We can sweep the input to find the best performance range:
Motu M6 USB Audio Interface Professional Monitor Out DAC THD vs Level Measurements.png

So the +16 dBu spec is confirmed.

Here is the dynamic range:
Motu M6 USB Audio Interface Professional Monitor Out DAC DNR Measurements.png

This gives us the 120 dB number given in the spec.

Multitone distortion is extremely good for an interface and in general:
Motu M6 USB Audio Interface Professional Monitor Out DAC Multitone Measurements.png


IMD is very good as well:
Motu M6 USB Audio Interface Professional Monitor Out DAC IMD Measurements.png


As is jitter:
Motu M6 USB Audio Interface Professional Monitor Out DAC Jitter Measurements.png


Same for linearity:
Motu M6 USB Audio Interface Professional Monitor Out DAC Linearity Measurements.png


Filter is as expected but with better attenuation > 24 kHz as I expected:
Motu M6 USB Audio Interface Professional Monitor Out DAC Filter Measurements.png

Motu M6 USB Audio Interface Professional Monitor Out DAC frequency response  Measurements.png


As a result, wideband THD+N measurement results are good for class:
Motu M6 USB Audio Interface Professional Monitor Out DAC THD vs Frequency Distortion Measureme...png


MOTU M6 ADC Measurements
DAC measurements went well seeing how we essentially achieved company specs. The situation reversed itself for input/ADC side. I used TRS cable as indicated which gave me 6 dB lower gain which was well needed. But when I fed the M6 a 4 volt signal and adjusted its gain to near 0 dBFS, I got severe distortion with SINAD dropping to just 39 dB! Backing off to -3.5 dB, regained fair amount of distortion:

Motu M6 USB Audio Interface Professional Monitor Out ADC Max Input Measurements.png


We can see the issue here as I sweep the levels:
Motu M6 USB Audio Interface Professional Monitor Out ADC THD vs Level Measurements.png

As you see, the input starts to saturate at around -10 dBFS. Going with the dashboard value, performance is good but could be better had this not been an issue:

Best audio interface review professional 2025.png


Which is sadly worse that MOTU M4.

IMD test confirms the same saturation issue:
Motu M6 USB Audio Interface Professional Monitor Out ADC THD vs Input Leavel Headroom Measurem...png


At least we are able to kind of get to +18 dBu spec, albeit with a lot of distortion.

Here is our dynamic range:
Motu M6 USB Audio Interface Professional Monitor Out ADC dynamic range Measurements.png


Finally, response is more or less frequency independent:
Motu M6 USB Audio Interface Professional Monitor Out ADC Distortion vs Frequency Measurements.png


EDIT: Line In 5 & 6 seem to have better specs so let's measure that:
Line In 5 & 6 ADC Measurements

18 dBu signal still causes saturation but not as bad as the combo inputs:
Motu M6 USB Audio Interface Professional Monitor Out ADC Line 5 6 18 dBu Measurements.png


Backing off to our standard 4 volts input, gets us much better results:
Motu M6 USB Audio Interface Professional Monitor Out ADC Line 5 6 4volt Measurements.png

Resulting in performance now matching the Motu M4:
Best audio interface review multichannel.png


We are still shy of the spec but if we sweep, we find that we can actually beat the it by a bit near clipping:
Motu M6 USB Audio Interface Professional Monitor Out ADC Line 5 6  THD vs Level Measurements.png


There is no improvement in dynamic range as predicted in above graph:
Motu M6 USB Audio Interface Professional Monitor Out ADC Line 5 6  Dynamic Range Measurements.png


So if you are willing to give up the trim controls, you can do better with Lines In 5 and 6 inputs.

MOTU M6 Headphone Amplifier Measurements
Headphone output is usually an after taught in many interfaces and such is the case here:
Motu M6 USB Audio Interface Professional Monitor Out Headphone Out Power 300 Measurements.png


Motu M6 USB Audio Interface Professional Monitor Out Headphone Out Power 32 Measurements.png


Conclusions
I was very hopeful that we had a good interface in our hands after testing the DAC. A number of issues I am used to seeing in MOTU interfaces were ironed out. Alas, the ADC performance was not able to keep up with the DAC. Seeing how this is the main job of an interface, I am somewhat disappointed although what it delivered is not too bad if you stay well away from 0 dBFS. Headphone output was not too bad at high impedance but awful with low.

I am going to recommend the MOTU M6 based on its reasonable price and doing well on DAC tests. It could have gotten higher rating if a bit more care was put in the ADC (or better specification on how to achieve their numbers).
------------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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Technical Specifications​

Sample rates44.1, 48, 88.2, 96, 176.4, 192 kHz
Mic/line/guitar4 x XLR/TRS "combo jack" mic/line/Hi-Z guitar inputsIndependent preamp gain, 48V phantom power and monitor switch for each input
Analog inputs2 x 1/4" line in
Analog outputs4 x 1/4" TRS line out (balanced, DC coupled)2 x 1/4" TRS stereo headphone with independent volume
Computer I/O1 x USB-C 2.0 audio class compliantCompatible with USB Type A host (*see power below)USB C-to-C and C-to-A cables included
MIDI I/O1 x MIDI IN1 x MIDI OUT16 MIDI channels to/from computer host
Headphones2 x 1/4" TRS stereo headphone with independent volume1 x 3-4 switch for optional monitoring of Line Out 3-4
Phantom power4 x individual +48V
Front panel2 x 1/4" TRS headphone output1 x potentiometer • monitor vol2 x potentiometer • phone vol1 x potentiometer • input monitor mix4 x potentiometer • mic/line/guitar input gain11 x switches • (4) 48V, (5) MON, (1) A/B and (1) 3-4160 x 128 pixel full-colored LCD with input and output level meters
PowerBus-powered through USB*Optional multi-blade international 15V DC power adapter (included), 1.0A max • tip pos or neg, supports 100-240V power sources (US/Japan, EU, UK, Australia)*USB bus power available with USB-C hosts only. For other hosts, use the included DC power adapter. For iOS devices with a Lightning port, an Apple Lightning to USB3 Camera Adapter is required (sold separately).
Dimensions and weight(width x depth x height, enclosure only)9.21 x 4.75 x 1.8 inches23.4 x 12.0 x 4.57 cm2.15 lbs / 0.975 kg
 
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Thanks Amir. I always look forwards to audio interface tests. I'm thinking about getting the 16A (2025) for use as 16ch home theater DAC. Sounds encouraging.
 
I read the spec as distortion and noise being down 110 dB which my measurements show to be conservative. Then again they also talk about 120 dB and I don't know how to achieve that. As is, performance is very good for an interface:
This gives us the 120 dB number given in the spec, albeit they say it is THD+N.

Where are you getting a claim of -120 dB THD+N? Seems pretty clear they are claiming 120 dB dynamic range.

It looks like the spec table in your review just has the headings shifted by one column which may be causing confusion.

1746139065872.png

1746139099860.png

1746139178364.png


Michael
 
Headphone output is usually an after taught in many interfaces and such is the case here:
*afterthought

And yes, that looks pretty naff, especially since the M2 was much better:
index.php

That was using an OPA1622.

The M6 result looks like a 4580/8080 opamp or something maybe?
 
I was rooting for this one as I was reading the DAC section. Too bad the ADC was a flop. No way I’d be able to trust I have the levels at the perfect “level” without spending more time and money than it’s worth (just to verify).

Thanks!
 
I was hoping the external power supply would unlock some additional performance over the M4, particularly in the headphone amp. I didn't realize it is only 500mA, which seems silly. Alas.
 
This is a review and detailed measurements of the MOTU M6 professional audio interface. It is on kind loan from a member and costs US $400 as of this writing.

View attachment 448083
The layout is clean as you see although that comes at the cost of not having input selection type (that is decided based on cable connection type -- see below). The LED have a grainy look to them but otherwise, nicely indicate clipping. Interesting to see dual headphone out, implying good drive capability. We will test this.

Power is provided through a 15 volt, 0.5 amp adapter (NOT USB):
View attachment 448085




Connector type
Dynamic range (A-weighted)THD+N (unweighted)Max level
Line Output1/4" TRS, balanced, tip hot120 dB-110 dB+16 dBu
Line Input1/4" TRS, bal/unbal, tip hot115 dB-107 dB+18 dBu
Mic inputXLR, balanced, pin 2 hot115 dB-129 dBu EIN+10 dBu (at minimum gain)
Phones1/4", TRS stereo115 dB-110 dB+12.5 dBu

It is unclear whether the achieved DNR and THD+N are at the max levels indicated or some other.

MOTU M6 DAC Measurements
Two outputs are provided: Line Out and Monitor Out. Later is impacted based on volume position. Performance was the same in both so I stayed with Monitor Out so I could adjust the levels as needed:

View attachment 448086
I read the spec as distortion and noise being down 110 dB which my measurements show to be conservative. Then again they also talk about 120 dB and I don't know how to achieve that. As is, performance is very good for an interface:

View attachment 448087

We can sweep the input to find the best performance range:
View attachment 448088
So the +16 dBu spec is confirmed.

Here is the dynamic range:
View attachment 448089
This gives us the 120 dB number given in the spec, albeit they say it is THD+N.

Multitone distortion is extremely good for an interface and in general:
View attachment 448090

IMD is very good as well:
View attachment 448091

As is jitter:
View attachment 448092

Same for linearity:

View attachment 448093

Filter is as expected but with better attenuation > 24 kHz as I expected:
View attachment 448094
View attachment 448095

As a result, wideband THD+N measurement results are good for class:
View attachment 448096

MOTU M6 ADC Measurements
DAC measurements went well seeing how we more or less achieved company specs. The situation completely reversed itself for input/ADC side. I used TRS cable as indicated which gave me 6 dB lower gain which was well needed. But when I fed the M6 a 4 volt signal and adjusted its gain to near 0 dBFS, I got severe distortion with SINAD dropping to just 39 dB! Backing off to -3.5 dB, regained fair amount of distortion:

View attachment 448097

We can see the issue here as I sweep the levels:
View attachment 448098
As you see, the input starts to saturate at around -10 dBFS. Going with the dashboard value, performance is good but could be better had this not been an issue:

View attachment 448099

Which is sadly worse that MOTU M4.

IMD test confirms the same saturation issue:
View attachment 448100

At least we are able to kind of get to +18 dBu spec, albeit with a lot of distortion.

Here is our dynamic range:
View attachment 448101

Finally, response is more or less frequency independent:
View attachment 448102

MOTU M6 Headphone Amplifier Measurements
Headphone output is usually an after taught in many interfaces and such is the case here:
View attachment 448103

View attachment 448104

Conclusions
I was very hopeful that we had a good interface in our hands after testing the DAC. A number of issues I am used to seeing in MOTU interfaces were ironed out. Alas, the ADC performance was not able to keep up with the DAC. Seeing how this is the main job of an interface, I am somewhat disappointed although what it delivered is not too bad if you stay well away from 0 dBFS. Headphone output was not too bad at high impedance but awful with low.

I am going to recommend the MOTU M6 based on its reasonable price and doing well on DAC tests. It could have gotten higher rating if a bit more care was put in the ADC (or better specification on how to achieve their numbers).
------------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
How does the 1/4 inch input know if your using a guitar? Guitar inputs are usually higher impedance and more gain.
 
I was hoping the external power supply would unlock some additional performance over the M4, particularly in the headphone amp. I didn't realize it is only 500mA, which seems silly. Alas.
At 15V its stiill delivers 50% more power than the M4 gets.
The USB connector says bus powered, does that mean you dont need the power supply?
 
At 15V its stiill delivers 50% more power than the M4 gets.
The USB connector says bus powered, does that mean you dont need the power supply?
According to the manual, it depends on your connection cable.
Connect the M6 to your host computer with the supplied USB cable. When the M6 is connected to a USB-C host computer or iPad, it can be powered by its USB connection to the host. When connected to a USB-A host computer, you’ll need to connect the DC power adapter to supply enough power.
Which leads me to believe USB-C is adequate to supply power (no surprise), but USB-A is not.
 
How does the 1/4 inch input know if your using a guitar? Guitar inputs are usually higher impedance and more gain.
I have wondered this about my M4 as well. Most interfaces have dedicated inputs or a button. I have assumed it is tied to switching jacks and TS vs.TRS plugs, but now that I think about it, that doesn't make any sense unless it is sensing continuity between 2 sets of contacts. Otherwise, it could be sensing gain and adjusting accordingly. The manual sheds no light on this. Guitars generally want to see a 1M input impedance similar to most guitar amps. In any case, my M4 works fine and feels decent for recording direct with a modeler plugin.

At 15V its stiill delivers 50% more power than the M4 gets.
The USB connector says bus powered, does that mean you dont need the power supply?
Good point. I missed the 15V rating.

IIRC, you don't need the power supply if you use a USB C source. If you are using USB A 2.0, you do need the PS.
 
Dedicated Line Ins (inputs 5/6) are rated better than the combo TRS/XLR inputs (inputs 1-4). Would be interesting to test those and see how they do.

It looks your -100 dB THD+N matches the spec for inputs 1-4. On the M4 you found a similar drop in performance with the combo inputs, so it isn't fair to compare the M4 and M6 using different inputs.

1746152637749.png


1746152294774.png

Michael
 
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Shame about this part;

1746152290695.png


Otherwise fine on other fronts... well HP amp section is not great either, but that is more expected. Cheers for the testing @amirm and thanks to the member that sent this in.


JSmith
 
Dedicated Line Ins (inputs 5/6) are rated better than the combo TRS/XLR inputs (inputs 1-4).
Ah! I missed this distinction. Will see if I can remeasure tonight.
 
Ah! I missed this distinction. Will see if I can remeasure tonight.
To be clear the reason for this is that inputs 5/6 don't pass through a (padded down) mic preamp.
 
Woo!! Thank you for testing this one out, a heap of us have been waiting to see some measurements. It's a bummer ADC isn't up to expectations... but at least the DAC will do for some great audio playback. It works but i'll hang onto my motu m2 for now.
 
The little I have played with (loopbacks) , I have seen much better performance for ADC at the two separate inputs.
Otherwise very decent overall.

Thanks Amir!
 
What DAC do the M4 and M6 use? As for analog out, the M6 seems to have solved the IMD hump problem of the M4, but harmonics have remained very similar, down to the HD3 sticking out.

The inputs seem to have gotten worse compared to the M4. In fact, I got so annoyed with the inputs of the M4 (HD seems to change minute to minute, gain adjustments are not consistent) that I bought an MkIV which has stellar performance even on the mic inputs.
 
What DAC do the M4 and M6 use?

The original M4 design used an ESS ES9016S but subsequent revisions use an ESS ES9026pro (same as UL Mk5). I haven't seen a teardown of the M6, but I assume it also uses an ES9026pro as the manual has the same specs for the M4 and M6. I believe the M4 design only used 6 of 8 DAC channels (4 for line outputs, 2 in parallel for headphone out), so adding another headphone out wouldn't require a new DAC chip.

EDIT: Confirmed ES9026pro -> https://prosound.ixbt.com/interfaces/motu-m6.shtml.

Michael
 
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