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Motu M4 Audio Interface Review

amirm

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#1
This is a review of Motu M4 4x4 audio interface (DAC and ADC). It is on kind loan from a member and costs US $220.

The enclosure is heavy gauge metal and sturdy:

Motu M4 4 channel Audio Interface DAC 4x4 Audio Review.jpg


The front inputs are for microphones with higher gain. For my testing I used the Line in (and out) in the back:

Motu M4 4 channel Audio Interface DAC 4x4 Back Panel Inputs Outputs TRS Headphone Amplifier Au...jpg


For testing I installed the ASIO drivers which came with a nice little control panel that lets you set the sample rate and buffer depth. I had no difficulty operating the unit during my testing.

And oh, there is a headphone amplifier in there also which I tested as well.

DAC Audio Measurements
I started my testing with the M4 acting as a normal DAC using its balanced TRS jacks:

Motu M4 4 channel Audio Interface DAC Audio Measurements.png


I don't know why but I expected the performance to be worse so was pleasantly surprised by the sum (ratio) of the noise and distortion in the form of SINAD. This places the M4 firmly in the top bracket of all DACs tested regardless of configuration:

Best audio interface review measurements.png


best audio interface review zoomed.png


Indeed it finishes just below Motu 624.

Dynamic range is very good, partly aided by more than nominal output voltage of 5.2 volts:
Motu M4 4 channel Audio Interface DAC Dynamic Range Audio Measurements.png


The default filter is not as sharp as it should be (typical) but has excellent attenuation:

Motu M4 4 channel Audio Interface DAC Filter Audio Measurements.png


Jitter is just shy of excellent:
Motu M4 4 channel Audio Interface DAC Jitter Audio Measurements.png


Multitone test shows a typical rise in distortion with frequency:

Motu M4 4 channel Audio Interface DAC Multitone Audio Measurements.png


Linearity (a measure of accuracy) was perfect:

Motu M4 4 channel Audio Interface DAC linearity Audio Measurements.png


Noise and distortion relative to frequency tells us what we already saw in multitone test:
Motu M4 4 channel Audio Interface DAC THD+N vs Frequency Audio Measurements.png


Unfortunately the IMD test relative to level took us back a year or more to when DACs had a "hump" (increase) in distortion at mid-levels:
Motu M4 4 channel Audio Interface DAC IMD Audio Measurements.png


Motu would do well to read the threads here with a solution to this problem.

ADC Audio Measurements
Reversing the tables, my analyzer fed the M4 an ultra clean sine wave and asked it to digitize it:
Motu M4 4 channel Audio Interface ADC Audio Measurements.png


This is with line in as indicated. With Mic in (not shown) and at minimum gain, SINAD drops just a few dBs to 100 or so. At higher gains it would go farther down to 94 dB or so. Back to Line In performance, this is good but some distance from state of the art:

Best Audio Interface ADC Review Measurements.png


The input is rated to 18 dBu which I used for most of the tests including this dynamic range:

Motu M4 4 channel Audio Interface ADC Dynamic Range Audio Measurements.png


Analog linearity was excellent:

Motu M4 4 channel Audio Interface ADC Linearity Audio Measurements.png


Frequency response at full 192 kHz showed some odd peaking:
Motu M4 4 channel Audio Interface ADC Frequency Response  Audio Measurements.png


IMD vs level shows the same issue we saw with the DAC:

Motu M4 4 channel Audio Interface ADC IMD Audio Measurements.png


It shows to some extent in THD+N versus level as well:

Motu M4 4 channel Audio Interface ADC THD+N vs Input Level Audio Measurements.png


THD+N versus frequency shows peaking at the extremes of frequency range:

Motu M4 4 channel Audio Interface ADC THD+N vs Frequency Audio Measurements.png


Overall the ADC is less impressive than the DAC section.

Headphone Amplifier Audio Measurements
Let's see if this is a purely checklist item or useful by measuring its power versus distortion+noise into 300 ohm first:

Motu M4 4 channel Audio Interface DAC Headphone Out Power into 300 ohm Audio Measurements.png


The darn IMD hump shows up here yet again. That aside, available power is modest at just 18 milliwatts. Best to use an efficient headphone.

Let's see how it does with 33 ohm load:

Motu M4 4 channel Audio Interface DAC Headphone Out Power into 33 ohm Audio Measurements.png


So power level is more or less the same. The good news is that output impedance is quite low so should not change the tonality of the headphone.

Conclusions
Despite its budget price and wealth of functionality, the Motu M4 delivers on DAC performance with ratings that hold up well against some of our best budget DACs. Its ADC as noted is a step behind but still much better a lot of PC interface cards and consumer interfaces. The headphone amp is the weakest part but still it serves to be usable.

Overall, the Motu M4 makes for a good option even for people who just want a DAC. It gives you the additional input functionalities to say, produce a podcast or youtube video. Or test audio gear (to its limit of course).

Overall, I am happy to recommend the Motu M4 Audio Interface.

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As always, questions, comments, recommendations, etc. are welcome.

It seems no matter how much you all donate money, I still crave more! So I thought we try to find my limit by having you all donate a ton of new money. Maybe that will stop my begging. So go deep in your bank account and donate heavily using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

617

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#5
The feature set for recording: monitoring individual inputs, separate phantom power, great useful meters, is unmatched at this price. Very nice unit if you need to get audio in or out of a computer. Latency is great, too, for vst instruments.
 

Tks

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#6
Did pretty good. For $220 and with the nice features, seems great for home use (finally someone woke up and decided on proper meters like RME does).

Is it possible to test 4V or 2V putput performance? I'm real curious how that does.

Really odd seeing some of the rising distortion especially considering how deep ESS chips attenuate (though they sadly chose a silly filyet as default instead of the brick wall, though that should be firmware fixable).
 

q3cpma

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#7
Very nice, makes the M2 quite attractive. I thought it was better than the Babyface, but after looking at both, the Babyface's THD+N being strictly defined by H2 and having basically nothing after H3 makes it better. Oh well, at 25% of the price, it's a beast.

I'm sure this question has been asked a hundred time already, but here we go: can't the AP compute Geddes' metric?
 

PeteL

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#8
Considering that every adc/dac combo sitting on the left of it on the SINAD chart is 5 times this price or more, and beating it by a low margin, I find it hard to not feel like it is a Home run. For me it is I a Golfing Panther, but I respect the verdict. Living at a time where a-98dB THDs at the bottom of the spectrum makes the ADC ''less impressive'' is certainly a great time for digital audio interface. Yeah, I Know, that ESS bump thing...
 
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#9
I'm looking for a quality interface to record my vinyl records via my separate RIAA preamp in 24 bit/96 kHz quality. Would this device work?

I would take the usb c output to usb A input of my windows 10 laptop.
 

Blumlein 88

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#12
I'm looking for a quality interface to record my vinyl records via my separate RIAA preamp in 24 bit/96 kHz quality. Would this device work?

I would take the usb c output to usb A input of my windows 10 laptop.
Yes
 
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#14
I almost ended up buying the M4 instead of my Topping DX7s - and I kinda regret not doing it. The low power headphone out turned me off, but as it is right now I only use high sensitivity headphones anyway.

I've already seen measurements, so the review is nothing surprising, but it just reaffirms that for the price the M4/M2 are impossible to beat in audio interface realm(correct me if I'm wrong).

Also, it might just be me, but I love the industrial design of the units.
 

MRC01

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#16
Looks like the value king of audio interfaces / mic preamps.

How do these things work with Linux? Linux can handle the USB audio source with built-in functionality, no drivers or apps needed. But it looks like each device has its own software app to set the sample rate and bit depth. So Linux users wouldn't be able to do that?

For example when I use my Zoom H4 as a mic preamp and USB interface. I set the H4 to apply 48V phantom power, set the gain for the mics, and set the bit rate & depth. Then I plug it into the PC via USB and the PC sees an SPDIF audio input. If the Zoom didn't have its own switches to set sample rate & bit depth, I could not do it from the PC.
 

Blumlein 88

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#17
Given the limited dynamic range and high distortion of vinyl, why use hi-res?
I've run into situations doing needle drops where there seems to be some interaction with peaky moving coils and the lower sample rates (less than good filters just past ultrasonic I suppose). Going to 88 khz or 96 khz takes care of it and the needle drop sounds same as the LP itself.
 

Blumlein 88

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#18
Looks like the value king of audio interfaces / mic preamps.

How do these things work with Linux? Linux can handle the USB audio source with built-in functionality, no drivers or apps needed. But it looks like each device has its own software app to set the sample rate and bit depth. So Linux users wouldn't be able to do that?

For example when I use my Zoom H4 as a mic preamp and USB interface. I set the H4 to apply 48V phantom power, set the gain for the mics, and set the bit rate & depth. Then I plug it into the PC via USB and the PC sees an SPDIF audio input. If the Zoom didn't have its own switches to set sample rate & bit depth, I could not do it from the PC.
The answer is kinda sorta. This review details the limited functionality with various linux kernals.

https://panther.kapsi.fi/posts/2020-02-02_motu_m4

Working with ASIO is something I wish linux would fix. I'd use no other OS if they could do that.
 

Tks

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#19
Just noticed, no mains noise at all from a bus-powered device. I imagined something would go wrong there if anywhere. Very interesting to see they managed USB2 spec but still managed a USB-C connector and didn't mess anything up.
 

JIW

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#20
I almost ended up buying the M4 instead of my Topping DX7s - and I kinda regret not doing it. The low power headphone out turned me off, but as it is right now I only use high sensitivity headphones anyway.

I've already seen measurements, so the review is nothing surprising, but it just reaffirms that for the price the M4/M2 are impossible to beat in audio interface realm(correct me if I'm wrong).

Also, it might just be me, but I love the industrial design of the units.
You could have used the built-in headphone output as an additional analog output connected to a headphone amplifier. At 2 V RMS (13 mW RMS into 300 Ohm) SINAD should be about 105 dB. Further, the built-in amplifier seems to be current limited to about 8-9 mA RMS (25 mA peak-to-peak maybe). Thus it can reach the specified output level of 12.5 dBu (3.27 V RMS) for a load (e.g. amplifier input impedance) of about 420 Ohm or greater.
 
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