MOTU M4 Loopback Measurements

[Evgeniy]

However, from the specs of Motu M4:

• DAC: ES9016 SABRE32 Ultra DAC
• ADC: AKM AK5552VN
• Preamp: THAT Corp 6263 preamplifier

The ADC has a THD+N of -106 dB and the DAC -110

OpAmp 's :
TI 1AW7 = TI opa1678 , low-cost OpAmp .
(Because OPA1678 in some case size's marked as AW7, see datasheet. )

 

[CerealKiller]

Hi, I have a question since you are a user of this interface, are the outputs 3 & 4 labled "Line Out" Fixed or variable volume?

Is it posible to get them to output fixed ? I'm planning on buying it to conect outs 1 & 2 to powered monitors and 3 & 4 to a Headphone amp.

Those where two questions, Thanks in advance.

 

[Severian]

Hi, I have a question since you are a user of this interface, are the outputs 3 & 4 labled "Line Out" Fixed or variable volume?

Is it posible to get them to output fixed ? I'm planning on buying it to conect outs 1 & 2 to powered monitors and 3 & 4 to a Headphone amp.

Those where two questions, Thanks in advance.

Yes, the 3/4 outputs are fixed line outs. I do exactly as you say and use the 1/2 outputs with volume control for my speakers and the 3/4 outputs to a headphone amp.

You could even run speakers and a headphone amp with the M2 model by using both the balanced and unbalanced 1/2 outputs, since they are active at the same time, so long as you didn't mind having an extra volume pot before your headphone amp.

 

[f1shb0n3]

I am using Motu M2 with studio monitors on TRS and Heresy amp on the RCA. Having to turn up the volume up on the Motu when using headphone amp is inconvenient but works fine. I have a remote on-off switch for the monitors so I can turn them off when using headphone amp.

Worst case is when I turn on my monitors and forget to dial down the volume on the Motu and the monitors explode at max volume. If you are using Motu M2 in a similar way make sure to not boost the volume on the powered studio monitors amp otherwise you might damage your hearing when this happens.

Because of this inconvenience I'm upgrading to M4 for the line out to headphone amp. I have a question about M4 in that use case - do you know if both output 1-2 and 3-4 can play the same audio from the computer?

 

[Severian]

I am using Motu M2 with studio monitors on TRS and Heresy amp on the RCA. Having to turn up the volume up on the Motu when using headphone amp is inconvenient but works fine. I have a remote on-off switch for the monitors so I can turn them off when using headphone amp.

Worst case is when I turn on my monitors and forget to dial down the volume on the Motu and the monitors explode at max volume. If you are using Motu M2 in a similar way make sure to not boost the volume on the powered studio monitors amp otherwise you might damage your hearing when this happens.

Because of this inconvenience I'm upgrading to M4 for the line out to headphone amp. I have a question about M4 in that use case - do you know if both output 1-2 and 3-4 can play the same audio from the computer?

I think you would need to use something like Voicemeeter's virtual output device to accomplish this.

 

[CerealKiller]

Yes, the 3/4 outputs are fixed line outs. I do exactly as you say and use the 1/2 outputs with volume control for my speakers and the 3/4 outputs to a headphone amp.

You could even run speakers and a headphone amp with the M2 model by using both the balanced and unbalanced 1/2 outputs, since they are active at the same time, so long as you didn't mind having an extra volume pot before your headphone amp.

Thanks Sev, thats really helpfull since its not clear in the user manual. One more question, are 3&4 treated as a separete audio device by os and media players? I mean, in a player like Foobar i.e. do you have to manualy select the outputs 1&2 or 3&4 or is it all treated the same as a single device? thak u very much in advance.

 

[Minigun]

Thanks Sev, thats really helpfull since its not clear in the user manual. One more question, are 3&4 treated as a separete audio device by os and media players? I mean, in a player like Foobar i.e. do you have to manualy select the outputs 1&2 or 3&4 or is it all treated the same as a single device? thak u very much in advance.

In Windows, after installing the driver, it's seen as two stereo devices, so you'd have to select one.
I use the M4 in Linux, where as a class compliant device it is seen as a 4-channel device. I believe it's also so on MacOS. I use a virtual device to duplicate a stereo signal into 4-channel signal, thus the output is channels 1/2+3/4.

 

[f1shb0n3]

There's a discussion about the M4 3-4 outputs at https://www.audiosciencereview.com/forum/index.php?threads/motu-m4-interest.11035/page-2

I posted a suggestion how to have a separate device in MacOS for 3-4 outputs without additional software by creating an aggregate device in Audio MIDI settings and changing speaker settings to use channels 3 and 4 for it. I can't confirm it works though as I have M2, it would be great if someone with MacOS and M4 can try it out and see if it does the job to have a separate device in MacOS for outputs 3-4.

 

[Alex___]

Hi, a couple of weeks ago, a Motu M4 came to me. I decided to test it in loopback mode. In loopback tests, the performance is worse than in tests using high-quality Audio Precision equipment, but nevertheless, someone may be interested. I made a balanced cable from a Canare StarQuad L-4E6S quad-pole microphone, REAN Connectors NYS202 (Neutrik) plugs.

The Motu M4 was connected to a Macbook pro (battery powered), tested via bootcamp on windows 10, the program in which tested RMAA
First test balanced TRS input 3,4; TRS output from 3,4 and 1,2.

Now test of the second (1-2) balanced input with combined XLR and TRS connectors, tested only TRS, level controls to minimum. Due to the fact that input 1-2 has a lower overload capacity of 16dbu, and the TRS 3-4 output is fixed at 18dbu, I had to do the test using MME and DirectSound to slightly reduce the output signal in the mixer.

The link can download pdf files in detail and save files to open in the rmaa program.
Motu M4 test loopback balance.

Now the unbalancetest. First test the TRS 3-4 input and 3-4 output (RCA) and 1-2 headphones output. I must say that the TRS input 3-4 (rear panel) is fixed and, accordingly, the 3-4 RCA output has 2 times less amplitude (-10dbu) compared to the balanced one, therefore the signal in RMAA was -8.4dB, from the headphone a little more output - 6.8 dB.

From 1-2Headphone out to (rear panel) input:

Now the TRS 1-2 (front panel), gain knob input is at minimum.

From HP 1-2 out to 1-2 input:

The link can download pdf files in detail and save files to open in the rmaa program:
Motu M4 test loopback unbalance (SE)

Comparison of Motu M4 when connected to an Apple Macbook Pro (2014) and MacMini (late 2018) laptop.
balanced input / output TRS 3-4 (rear panel):

when testing with the same outputs / inputs, there is no difference between a macbook (when powered by a battery) and a mac mini (powered by 220v), there is no difference in measurements at all, no interference, everything is in a minimum error. As you can see, Apple Mac mini and Motu M4 do not need any USB noise suppressors and other usb power decoupling that some users use. Test Motu M4 macbook vs mac mini.
sorry for my English

 

[AllanDavidson]

Hi, a couple of weeks ago, a Motu M4 came to me. I decided to test it in loopback mode. In loopback tests, the performance is worse than in tests using high-quality Audio Precision equipment, but nevertheless, someone may be interested. I made a balanced cable from a Canare StarQuad L-4E6S quad-pole microphone, REAN Connectors NYS202 (Neutrik) plugs.

Thank you for your test!

I think your results may be a tad worse than amirm's, because he tested both DAC and ADC isolated with his AP tester, one after another, while your tested both DAC/ADC in chain with the RMAA software.

 

[trl]

According to specs sheet and manual it has 16 dbu max output on RCA and line outs. That should be about 4.9 volts. Unless you have measured it and found the spec sheet wrong (which it could be).

Also are the TRS inputs on the front panel switchable between line and instrument in the software? If not those have a 1 megaohm input impedance. For testing purposes the rear line in jacks will have a lower input impedance and slightly lower noise and distortion. So using those for testing should work the best. Your results indicate the best performance with those rear line ins.

Thanks, I just cancelled my M2 order from Thomann and ordered a M4 instead. Also @Alex___ measurements confirm your thoughts here: https://www.audiosciencereview.com/...tu-m4-loopback-measurements.10890/post-514273. Thanks both!

 

[trl]

M4 delivery time changed to 12-15 weeks on Thoman, after already waited for over 3 week. Quite frustrating.
However, I will probably change the order for a Clarett 2PRE instead, most likely similar DAC & ADC quality, same digital volume control, but I will miss the front LCD for sure and the RCA output from the M4.

 

[L5730]

M4 delivery time changed to 12-15 weeks on Thoman, after already waited for over 3 week. Quite frustrating.
However, I will probably change the order for a Clarett 2PRE instead, most likely similar DAC & ADC quality, same digital volume control, but I will miss the front LCD for sure and the RCA output from the M4.

The M4 has another pair of line inputs 3/4, but not ADAT optical digital input. I'd have thought that would be the biggest difference between these units in terms of usage. I'd have said the Motu M2 would be more similar, as it just has 2 analogue inputs - save yourself some money.

It's annoying when you order something and the time scales change, and so drastically. It seems these Motu units are awfully popular and there is a struggle to keep up with demand.

 

[trl]

The M2 has no real line input, this is why I initially chose the M4.
Also, the M2 has an ETA of 2-3 weeks that might also become 12-15 weeks soon too.

 

[L5730]

The M2 doesn't have a line input, but the Clarett Pre2 does?
They both look to have Mic/Line/Instrument combi with a variable pre-amp in front. The M4 has an additional pair of inputs, fixed gain.
Oh I see, ADC is 10dBu in Motu M2 vs. 18dBU in M4 (3/4) vs. 26dBu in ClarettPre2. Quite a difference and would need an attenuator for particularly hot 'pro' signals.

 

[trl]

This has been discussed already in a different thread, not sure where right now. Please check M2/M4 datasheet and look for the 1 MOhms input impedance for the M2 that means that this is not a real line input, but more like an instrument input that is able to accommodate line level signals too.

The Clarett seems to have a real line input, at least by looking at the input level requirements. However, I own a Solo Gen3 and I never had any issues feeding it will line-level signals, so this is why I am confident that Clarett should do just fine in this area.

 

[jtwrace]

I was able to get an M2 from Sweetwater last week. I'm really impressed for the money.

 

[trl]

I got a measurement pretty close with what @L0rdGwyn did when connected the 3/4 Line inputs from the back wth the 3/4 Line outputs (or 1/2 outputs to the max). That corresponds to about 4.6V RMS:

Line In 3/4, Line Out 3/4 @4.6V RMS, SINAD of 100dB ​

Problem is that using 2V RMS or 1V RMS on the inputs 1/2 (because inputs 3/4 are not gain adjustable) will increase the noise a lot, no matter I'm using Line or Mic from Inputs 1/2.

Line In 3/4, Line Out 3/4 @2V RMS, SINAD of 93dB

​

This is even worse than my Scarlett Solo Gen3 from below:

Line In TRS, Line Out TRS @2V RMS, SINAD of 95dB

​

And definitely worse than the Clarett 2Pre USB from below:

Line In TRS, Line Out TRS @2V RMS, SINAD of 102dB

​

I see no reason to have an interface measured at it's min. input level, while the inner ADC is mostly used at 1V or 2V RMS when measuring external audio interfaces or is feed with few mV from external mics.

I'm somehow confused about the mixed measurement I got for the M4.

 

[aos]

I just got M4 and was trying to do loopback measurements with Arta but I don't see how people are able to measure it because the most you can get is like -17.5dB when the output is at -3dB. In other words the output does not have enough voltage swing to saturate the input. I am using TRS cables for loopback from line output 3 to line input 3 on the back of the unit. I just changed the output from line to monitor (1) and now I get a bit more, -8.6dB versus previously . But the input monitor still shows a lot of headroom left. I must be missing something basic? The output and input were calibrated and for -3dB@400Hz I seem to get 1.83Vrms. Which is bizzare because both outputs 1 and 3 produce same 1.83Vrms at -3dB yet the monitor output gives significantly closer to -3 during actual test.

 

[trl]

I am using TRS cables for loopback from line output 3 to line input 3 on the back of the unit.

I've used the same and i got -3.2dB. Not sure what needs rechecked in your setup, unless the cables are having issues (very unlikely I'd say).
I get the same figures with both Windows MME and ASIO drivers.

Which is bizzare because both outputs 1 and 3 produce same 1.83Vrms at -3dB yet the monitor output gives significantly closer to -3 during actual test.

Playing a 440Hz sinewave @0dB should get you at least 4.6V RMS on both 3/4 and 1/2 outputs (volume to the max. for 1/2 output).