Motu M4 Audio Interface Review

[buedi]

Thank you @Stratocaster for your reply. I ordered the adapter now.

I just wonder why the Motu documentation specifies 3.6V OUT for the TRS part of the XLR/TRS combo socket when there are no 3.6V delivered.

Or do I think in the wrong direction and they mean that you are not allowed to send in more than 3.6V into the TRS socket to the Motu to not damage it? Then I wonder why they did not specify it as max 3.6V IN instead of out.

 

[phoenixsong]

You shouldn't need to turn on phantom power to use the boom mic in the first place though?

 

[buedi]

Hi @phoenixsong,

Phantom Power is only delivered on the XLR part, which is good. I suppose 48V would fry most Mics on the TRS port The manual also states that phantom power is not delivered to the TRS part, but it also states that there should be a max of 3.6V.
It is in the M_Series_User_Guide.pdf, Appendix B - Audio Specifications - MIC in - TRS (Page 25).

Exact words:
Maximum output voltage: 3.6V

You are able to connect a simple, non self-powered Microphone to the TRS port and it works? Then my unit might indeed be broken.

 

[AnalogSteph]

You are able to connect a simple, non self-powered Microphone to the TRS port and it works? Then my unit might indeed be broken.

It should work with a dynamic mic just fine, although input noise level should be substantially higher than via XLR due to the added buffer amplifier. (We are talking the TRS part of the front combo jacks. The extra line-in on the M4 seems to be fixed gain for high-level signals only, accepting up to +18 dBu.)

Your problem seems to be having an electret (or MEMS) microphone that requires Plug-in Power to be supplied from the mic input in order to work. You need a consumer microphone input for that. The M4 is not equipped to support such gear, although it should be easy for a seasoned electronics tinkerer to make an external mic power supply since the required circuitry is dead simple (jacks, a battery w/ holder and power switch, one bias resistor and one coupling capacitor each per channel; e.g. 1x 3V Lithium primary cell or 2x AAA, 2.2 kOhms and 1 µF or so), it must be shielded though. With that added in front of the TRS input, things should start working.

 

[weesch]

hi
i use 48 v http://recordinghacks.com/microphones/Apex-Electronics/190
with a yamaha 01v96 at 44.1 khz
here a audio demo here

guitar and voice was recorded with this microphone
the sound is good no hum ....maybe + or - 20 db on 01v96 that's all

 

[buedi]

Your problem seems to be having an electret (or MEMS) microphone that requires Plug-in Power to be supplied from the mic input in order to work.

You are right and this is what I am talking about. My Mic requires ~2V and can work with 1-10V according to the manufacturer. The manual of the M4 states that the Mic In TRS part has a maximum OUTPUT of 3.6V. Neither the MOTU support, nor the distributor over here did answer to my question if the manual is just wrong or if my unit is broken.

I am prettty sure that since no other device i have seen with those combo jacks provides output power on the TRS part, that just the manual is wrong and whoever wrote it wanted to put the 3.6V maximum output power into the table for the description of the TRS Line outs of the MOTUS. From what I have read, they provide a maximum of 3.6V.

I ordered a Rode VXLR+ now which should arrive some time next week and I think that should make my Microphone working. But I will still return the M4 if the documentation is right and it should provide 3.6V on the TRS Mic In and try to get a unit that is OK. Unfortunately I do not have any equipment to measure this, so I hoped someone with an M4 can measure the TRS Mic In, because MOTU does not seem to answer questions about their manuals :-(

 

[Stratocaster]

I really don't know about the 3.6V output power on the TRS jack...

But what i know, that regular PC (electret) mics usually don't work on audio interfaces. But you can get them to work with adapters like the VXLR+ or others. I have tried this before on multiple interfaces and it just works great. They will convert your 48V of phantom power on the XLR input to the needed 3-5V for your PC hadset / microphone.

And please remember to not plug and unplug devices into your audio interfaces XLR port while phantom power is enabled. First plug in your device (VXLR+ and Mic) then enable phantom power and the other way round. Otherwise you will risk to damage your gear.

 

[AnalogSteph]

There was a Japanese teardown video of a new revision M2 or M4 posted here somewhere, complete with some circuit analysis... pretty sure that there was a just an OPA1678 as a unity-gain buffer for the TRS. Besides, input impedance on something with plug-in power tends to be dominated by the bias resistor, which has to be in the low kOhms for the typical 0.5 to 0.75 mA current requirements... the TRS input is rated at 1 Megohm unbalanced.

I'm pretty sure that it's just an error in the manual as suspected and they meant to write input voltage instead.

 

[trl]

Thank you for the data point! This seems to support my suspicion that the M2/M4 might have a fundamental flaw, either in firmware or hardware.

Checking what @drake5000 wrote about his adapter and I see that he posted a link from where I got the below pic (source: https://www.zachpoff.com/resources/testing-xlr-adapters-with-plug-in-power/):

So it seems that mic's Signal is inverted with Ground in the 3.5mm plug. I wonder if this problem might be the reason why these adapters are not compatible with the M2/M4 interfaces.

 

[trl]

There was a Japanese teardown video of a new revision M2 or M4 posted here somewhere, complete with some circuit analysis... pretty sure that there was a just an OPA1678 as a unity-gain buffer for the TRS.

Six of them, actually: four for TRS and two for RCA, chec k this out: https://www.audiosciencereview.com/...analysis-and-few-in-house-measurements.17819/.

 

[weesch]

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:

View attachment 81052

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

View attachment 81053

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:

View attachment 81055

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:

View attachment 81056

View attachment 81057

Indeed it finishes just below Motu 624.

Dynamic range is very good, partly aided by more than nominal output voltage of 5.2 volts:
View attachment 81058

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

View attachment 81059

Jitter is just shy of excellent:
View attachment 81060

Multitone test shows a typical rise in distortion with frequency:

View attachment 81061

Linearity (a measure of accuracy) was perfect:

View attachment 81062

Noise and distortion relative to frequency tells us what we already saw in multitone test:
View attachment 81063

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:
View attachment 81064

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:
View attachment 81065

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:

View attachment 81066

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

View attachment 81067

Analog linearity was excellent:

View attachment 81068

Frequency response at full 192 kHz showed some odd peaking:
View attachment 81069

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

View attachment 81070

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

View attachment 81071

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

View attachment 81072

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:

View attachment 81073

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:

View attachment 81074

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.

-----------
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/

hi
can you tell us what is the ASIO latency ( in millisencond or samples ) at 44.1 khz
for
32 buffer :
64 buffer:
128 buffer:
256 buffer:
512 buffer:
1024 buffer:
and the performance with what type of computer and plugins you use (not in asio direct monitoring)
( motherboard /cpu / ram / harddisk / cubase )
because with my old protools hd 10 pci-x 64 bit 133 mhz with an old lga 775 computer / ssd sata 2 / win7x64 i have :
64 samples / 1.3 millisecond with all rtas / transvst aax 32 bit plugins
thanks a lot
best regards weesch

 

[mightycicadalord]

Here is m4 at 44.1, have to set it to 96k to get numbers under or around 5ms. I usually work at 48khz for video compatibility reasons. One annoyance I have is the 2048 buffer is not an option at 44.1 and 48khz. I often switch to the built in FL ASIO driver to get access to a 2048 buffer, lets me continue mixing on nearly finished projects while the motu is underrunning like crazy at 1024.

I'm kinda surprised the RTL is this high, I've been considering trying out that antelope synergy go for the dsp plugins while tracking. I never did feel like tracking things felt very good on the motu m4, even with the latency offset selected which seems to lower latency but less than 1ms on the lower buffers.

 

[VNN77]

Is there a way where I can split mic output? my mono mic (sm57) comes out only in the left ear cuz the input is chained together (in 1-2). They should add 1 channel option in the windows recording settings.

 

[memphiskat]

Hello,

I purchased the M4 to use mostly to transfer my late friends live master cassette recordings (mostly Grateful Dead).
I have it setup with my cassette deck's unbalanced outputs going direct into the M4 using TS 1/4inch adaptors on RCA cables.
The M4 is connected to my laptop via USB and I'm using Audacity to record.

I tried both the front combo inputs and the rear line inputs. When I use the front inputs and set the gain levels to peak around -6 or so I get good levels, but when I turn the "input monitor knob mix" between "input" and "playback" the sound changes dramatically (in volume slightly, but in timbre much more). This is with no effects or plugins in use. If I use the rear line inputs, which have a fixed input level, the levels peak @-16, but when I swing from "input" to "playback" the sound is identical. I assume this low level is the result of the fixed line level inputs set for a balanced level and I'm using an unbalanced connection.

My first question is why this change between input and playback on the front inputs verses zero difference on line inputs?

Second, If I understand Amirm's review correctly, he found that the rear inputs gave measurably better ADC results. So my question is should I be concerned about the lower recorded levels on the line input. Obviously I can raise the levels in software when editing/mastering, but does the higher recorded levels obtained with the adjustable gain front inputs outweigh the improved ADC results from the line level rear inputs?

 

[Stratocaster]

Is there a way where I can split mic output? my mono mic (sm57) comes out only in the left ear cuz the input is chained together (in 1-2). They should add 1 channel option in the windows recording settings.

Apparently not, i already contacted Motu about a year ago regarding this problem because in some software (e.g. VOIP) you have no option to configure the input leading to the behaviour you describe that you only have audio on one side.

If you use a DAW you have to set your recording track to mono or use some other tool that can sum your input.

I also was hoping that Motu would fix this issue to at least give the option to put it in single channel / mono mode but there was no such firmware / driver update so far.

In their response they also suggested to use 3rd party software like Voicemeter or software that uses or allows mono inputs in general.

 

[Lambda]

I also was hoping that Motu would fix this issue to at least give the option to put it in single channel / mono mode but there was no such firmware / driver update so far.

This is feature that shuld be in your operating system or application not in your audio interface.

 

[Stratocaster]

This is feature that shuld be in your operating system or application not in your audio interface.

It's a driver thing. When i think about it, most if not all my other interfaces offer the option to run 1 channel mode in windows.
Motu just decided to not implement 1 channel support in their drivers. But they told me they will consider to in the future with the next update.

 

[sharpty]

There's some new driver updates for Windows and a new Firmware update tool. Still no firmware update available for my M4 version 1, but windows does recognize it now.

 

[Backflash]

Hm, my m2 firmware is 2.0 is it the last one? motu download page says v2021.12
I have to say, it feels really nice to get driver updates for audio hardware, things I used before felt abandoned. And I think my Realtek driver is 2 years old.

 

[mightycicadalord]

Huh, I'm skeptical of the improved performance of asio clients at low buffers but I have a project that was giving me problems at 64 samples, I had it at 256 to be able to work without pops and such. I tried this driver and it can go through the whole song at 64 without any underruns. Interesting.

I'm soooo glad they added 2048 and 4096 at the 44.1 and 48khz settings, really need those when working on big projects at the end and buffer needs maxed.