Motu M4 Audio Interface Review

[amazingtazing]

Nothing wrong with using the full range of the dial, I'm not sure why you would want to, or expect to use 1/2 the range to begin with. Arguably it's better to keep the level higher at the source, than to add more gain (or less attenuation?) at the speaker.

I know it's not a direct comparison to working in a DAW with unprocessed tracks, but for playback thru Spotify etc. my LSR 305's are set to +4dBu and 7/10 on the rear volume control, I have a -4dB pad set using EQ APO (to avoid Windows CAudioLimiter), and I can easily drive the JBLs to audible distortion without maxing out the knob on the M4. Usually I have the M4 at 12-1 o'clock for near-field playback, but at 3 o'clock it's enough to fill my (relatively small) room.

Based on the manuals, the M4 should be capable of overdriving the input of the 305's when set to -10dBv, so I'd leave it at +4dBu unless you actually run out of range on the M4 dial for some reason. Just my 2c.

What volume do you usually have in Windows with EQ pad enabled? 100%?

 

[sharpty]

What volume do you usually have in Windows with EQ pad enabled? 100%?

Yep, 100% in Windows volume control.

 

[AllanDavidson]

Good upgrade either way. These MOTUs are getting seriously close in performance to the next tier up, and you've got more inputs and outputs to boot. And should they ever run out of ESS 9016s, some 9026s would basically drop right in if memory serves.

Well, it looks like you were right. Now revisions are coming with 9026 Pro (same DAC on Ultralite mk5) instead of the previous 9016S, and a new USB interface chip.

Not that it matters much, anyways, the DAC is already an 8-channel, 32bit/384KHz with 124db DNR and -110db THD, this is (I believe) beyond what any person would need.

I think a better ADC would benefit this unit enormously, since it's it's bread-and-butter, probably the main function of a portable interface. If you ever need better pre-amps or headphone amp down the road, you can just hook them up to the interface.

 

[Eccentricity]

Hello!

Has anyone tried using a 3.5mm ↔ XLR adapter with the Motu M4/M2? These adapters convert 48V phantom power to ~5V power for electret/bias microphones. Examples of such adapters;

• RODE VXLR+
• MOVO FXLR
• Antlion XLR power converter

I am experiencing a loud, low, airy hum when an adapter of this type is connected and powered with 48V. This is regardless of whether a microphone is actually connected to the adapter. Tapping or rubbing the adapter housing with no mic connected is actually audible, and is picked up in recordings. This audio is taken from my Motu M2 + Antlion adapter, and this audio is someone else's experience with a Motu M4 + VXLR+.

Reviews for this type of adapter seem to generally be positive overall, with no mention of the addition of this kind of noise on other interfaces, mixers, etc.

Has anyone else experienced this noise with this type of adapter on the Motu M4/M2? Is this possibly an inherent problem with the M4/M2?

 

[mightycicadalord]

They say. that the Input/Playback control only works if the MON button is enabled. A strange Motu solution in my opinion.

It makes sense to me, with the mon off on the inputs, you would be mixing between USB and silence.

 

[drake5000]

Hello!

Has anyone tried using a 3.5mm ↔ XLR adapter with the Motu M4/M2? These adapters convert 48V phantom power to ~5V power for electret/bias microphones. Examples of such adapters;

• RODE VXLR+
• MOVO FXLR
• Antlion XLR power converter

I am experiencing a loud, low, airy hum when an adapter of this type is connected and powered with 48V. This is regardless of whether a microphone is actually connected to the adapter. Tapping or rubbing the adapter housing with no mic connected is actually audible, and is picked up in recordings. This audio is taken from my Motu M2 + Antlion adapter, and this audio is someone else's experience with a Motu M4 + VXLR+.

Reviews for this type of adapter seem to generally be positive overall, with no mention of the addition of this kind of noise on other interfaces, mixers, etc.

Has anyone else experienced this noise with this type of adapter on the Motu M4/M2? Is this possibly an inherent problem with the M4/M2?

It’s an interesting finding. Thank you for sharing. I wonder if it has something to do with strange anomaly discovered by Julian Krause in his Motu M2 review: when no mic drawing phantom power there was an audible low frequency hum. And it went away after connecting proper condenser mic or turning phantom power off:
(Starts at 6:10)

So might be low impedance load such as these adapters results in similar behavior to zero load.

 

[mightycicadalord]

I turned on phantom for 1-2 on my m4, loaded up voxengo span and set the range low to max, so the bottom of the analyzer is at -180db. I'm getting a super clean "signal" if you will, no low end hum or anything in the analyzer or that I can hear. Not much but help but hey.

 

[trl]

when no mic drawing phantom power there was an audible low frequency hum. And it went away after connecting proper condenser mic or turning phantom power off

Not quite a real life scenario after all, right? Nobody will ever use an audio interface with no mic connected and phantom power in ON position. Who's using it for measurements will definitely connect something on its inputs and will need to not turn on the 48V.

However, his finding it is interesting indeed.

 

[Eccentricity]

Not quite a real life scenario after all, right? Nobody will ever use an audio interface with no mic connected and phantom power in ON position. Who's using it for measurements will definitely connect something on its inputs and will need to not turn on the 48V.

However, his finding it is interesting indeed.

To be as clear as I possibly can: the hum/noise persists as long as the adapter is connected, regardless of whether a microphone is connected. Simply having the adapter connected and phantom power on is enough to cause both the hum, and (at least in my case) the ability for the adapter to act as a microphone itself, in any scenario.

The first adapter I bought exhibited this behaviour, so I bought a second, and the same issue was observed. Assuming both adapters aren't faulty, it means the Motu is possibly doing something unexpected compared to other audio interfaces/mixers where this type of adapter appears to work correctly and as-expected.

An additional piece of information I recently discovered, is that having the adapter connected to one XLR input with phantom power on, then enabling phantom power on the second XLR input (even with nothing connected, so it's input is totally silent) causes the first input to experience a momentary spike in both volume and pitch of the hum/noise, before returning to the previous volume and pitch.

Recap;

• This issue appears to be exclusive to using an XLR ↔ 3.5mm adapter with 48V → ~5V phantom power conversion on the Motu M2/M4 series
• Noise is present as long as adapter is connected and phantom power is on; connecting a mic does not change or attenuate the noise
• Enabling phantom power on the other XLR input causes the noise to momentarily spike in both pitch and volume
• Identical noise is present when testing two identical adapters, insinuating that the adapters are not at fault
• Native XLR microphones do not produce the effect

Are there any members here that have a Motu M2/M4 and an XLR ↔ 3.5mm adapter with 48V → ~5V phantom power conversion? Any brand will do, I think (RØDE, Antlion, or MOVO). I'd like to corroborate my findings.

 

[Eccentricity]

Small update: I asked Julian Krause if he experiences the same noise I am hearing when using one of these adapters with the MOTU M2/M4, and it turns out he does:

My question:

Julian, have you tested an XLR ↔3.5mm adapter with 48V → ~5V phantom power conversion with the Motu M2 or M4? These include the RØDE VXLR+, Antlion XLR power converter, and the MOVO FXLR. I am experiencing a low, airy hum that doesn't seem to be present in reviews of these adapters when used with other interfaces or mixers. It might be an amplification of the low hum you experienced, and I'm curious if the Motu M2/M4 line is doing something abnormal compared to other interfaces.

His response:

Hey, I made a quick test with my RODE VXLR+ and the M2 and I get the same noise. I also tried two other active XLR to 3.5 mm adapter and they show the same behaviour. This seems to have to do with the problem I describe at 06:13. With condenser mics this isn't a problem as they draw enough power, so that this low frequency hum goes away. I suspect, that the Rode VXLR+ and the connected mic do not draw enough power for this problem to disappear and that's why the noise stays audible.

I asked a followup question; curious as to whether this hum is present on other interfaces. We'll see if that reveals anything.

 

[artburda]

To be as clear as I possibly can: the hum/noise persists as long as the adapter is connected, regardless of whether a microphone is connected. Simply having the adapter connected and phantom power on is enough to cause both the hum, and (at least in my case) the ability for the adapter to act as a microphone itself, in any scenario.

The first adapter I bought exhibited this behaviour, so I bought a second, and the same issue was observed. Assuming both adapters aren't faulty, it means the Motu is possibly doing something unexpected compared to other audio interfaces/mixers where this type of adapter appears to work correctly and as-expected.

An additional piece of information I recently discovered, is that having the adapter connected to one XLR input with phantom power on, then enabling phantom power on the second XLR input (even with nothing connected, so it's input is totally silent) causes the first input to experience a momentary spike in both volume and pitch of the hum/noise, before returning to the previous volume and pitch.

Recap;

• This issue appears to be exclusive to using an XLR ↔ 3.5mm adapter with 48V → ~5V phantom power conversion on the Motu M2/M4 series
• Noise is present as long as adapter is connected and phantom power is on; connecting a mic does not change or attenuate the noise
• Enabling phantom power on the other XLR input causes the noise to momentarily spike in both pitch and volume
• Identical noise is present when testing two identical adapters, insinuating that the adapters are not at fault
• Native XLR microphones do not produce the effect

Are there any members here that have a Motu M2/M4 and an XLR ↔ 3.5mm adapter with 48V → ~5V phantom power conversion? Any brand will do, I think (RØDE, Antlion, or MOVO). I'd like to corroborate my findings.

I have a Motu M4 and a Røde VXLR Pro adapter. Just ran some tests with the adapter plugged in without a mic and was watching the RTA in REW and was also monitoring. No hum, nothing like that. Very low noise floor. Only thing I noticed is a short jump of the noise floor in the lower frequencies when you turn on or off the phantom power of either one of the preamps. However, the VXLR Pro is a bit different than VXLR+, because when you plug a XLR cable into it and connect it to the preamp the connection stays balanced only the TRS connection to the microphone is unbalanced. That way you could use that sort of microphone over longer distances without the drawbacks of an unbalanced connection.

 

[sharpty]

Interesting theory about the power draw. The only 3.5mm to XLR adapter that I could find a detailed spec sheet for, the MZA 900 P from Sennheiser, shows a phantom power draw of 2.8mA, which is on par with many XLR condenser mics.

 

[Eccentricity]

I have a Motu M4 and a Røde VXLR Pro adapter. Just ran some tests with the adapter plugged in without a mic and was watching the RTA in REW and was also monitoring. No hum, nothing like that. Very low noise floor. Only thing I noticed is a short jump of the noise floor in the lower frequencies when you turn on or off the phantom power of either one of the preamps. However, the VXLR Pro is a bit different than VXLR+, because when you plug a XLR cable into it and connect it to the preamp the connection stays balanced only the TRS connection to the microphone is unbalanced. That way you could use that sort of microphone over longer distances without the drawbacks of an unbalanced connection.

Thank you very much for your testing! I am aware of the VXLR Pro and it's benefit over the VXLR+ (balanced output), and I'm glad to hear it apparently doesn't cause the same noise/hum as adapters that do not convert to balanced.

If nothing else, it might be a workaround (albeit it an expensive one) to this issue. I am very curious to discover whether other interfaces experience the same noise with the (non-balanced output) adapters.

 

[trl]

To be as clear as I possibly can: the hum/noise persists as long as the adapter is connected, regardless of whether a microphone is connected.

I don't think Julien is speaking about any adapter on his video, but about a missing mic while pushing the 48V switch, which may generate a hiss noise. This is something I can test myself as well on my M4, if needed, but if you're looking for something else, like connecting a 3rd party adapter and test for the noise, I cannot help.

 

[Eccentricity]

I don't think Julien is speaking about any adapter on his video, but about a missing mic while pushing the 48V switch, which may generate a hiss noise. This is something I can test myself as well on my M4, if needed, but if you're looking for something else, like connecting a 3rd party adapter and test for the noise, I cannot help.

I don't mention Julian in the post you are replying to. Regardless, he refers to the sound he hears in his video as a "low frequency hum", not a hiss, and labels it abnormal as such. That aside, I did explicitly state that the issue I am experiencing is while using a very particular kind of adapter.

The reason I brought up this issue in the first place, is that it appears that the MOTU M2/M4 may be the only interface that presents this issue, as other interfaces do not seem to have any issues with the aforementioned adapters. If this is true, it means there may be a fundamental or inherent issue with the MOTU M2/M4 interfaces not present in competitor devices. My sample size is small however, so I am soliciting additional info to corroborate my findings.

Lastly, my subsequent post mentions that Julian just recently tested this type of adapter in response to a question of mine; he experiences the same issue, whether the adapter is alone, or has a mic connected to it.

You are correct though, in that I would need others with either the M2 or M4, and an adapter of this type in order to gather more data.

 

[drake5000]

Thank you very much for your testing! I am aware of the VXLR Pro and it's benefit over the VXLR+ (balanced output), and I'm glad to hear it apparently doesn't cause the same noise/hum as adapters that do not convert to balanced.

If nothing else, it might be a workaround (albeit it an expensive one) to this issue. I am very curious to discover whether other interfaces experience the same noise with the (non-balanced output) adapters.

I have behringer UMC204HD and Mouriv 35C-XLR PRO (and all these chinese adapters are esentially the same). With this setup I have no problems whatsoever. No additional noise/ hum etc.

 

[Eccentricity]

I have behringer UMC204HD and Mouriv 35C-XLR PRO (and all these chinese adapters are esentially the same). With this setup I have no problems whatsoever. No additional noise/ hum etc.

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.

And yes, you are absolutely right that these adapters are all basically the same thing, which is why I've been careful to call out the issue as occurring with this type of adapter, rather than any one specific adapter.

 

[somebodyelse]

Since some people can recreate the issue and others can't it's probably worth checking which hardware, firmware and driver versions they have. https://www.audiosciencereview.com/...u-m4-audio-interface-review.15757/post-853638 has some pointers on hardware version.

 

[Buckster]

I've owned my Motu M4 for around a month now - not using for recording - just music production (amateur !) and listening of music.

It just sounds superb whether near field to my LSR 305s or via headphones to my sure 840s. I always can tell when a DAC/amp gets it right - as doesn't matter what I listen to - it always sounds great - detailed but without sibilance - lower end timing is great too (rubbish way of describing but with a poor DAC/amp bass can sometimes sound muddy).

My firmware says 2. something so I'm assuming newer design.

I've had plenty of hifi systems years ago when I was into hifi when some things sound great and others not. This just sounds fantastic all the time

same as my Denon 7200 av amplifier - I really rate the DAC (and design around the DAC) on that too (I think that one uses AKM 4490s)

 

[Eccentricity]

I have my own new data point to add: the test @artburda did with the MOTU M4 and the RØDE VXLR Pro matches my experience. I purchased a VXLR Pro and the MOTU M2 does not produce the hum/noise I experienced with the adapters that only convert 48V to ~5V.

That means this new adapter essentially bypasses the problem, though I am curious as to why this behaviour is present with adapters that do not convert to balanced.