MOTU M2 loopback measurements

[lc155]

It matters when you use the ADC for measurements. Many DACs have a flatter passband response than these AKM ADCs.

So for the product's intended usage of recording and playing back audio, no perceptible difference. Gotcha.

 

[bennetng]

So for the product's intended usage of recording and playing back audio, no perceptible difference. Gotcha.

Actually, it was Amir who mentioned about the ripples:
https://www.audiosciencereview.com/...00s-adc-comp-to-rme-adi-2-pro.3143/post-78592

Obviously MC_RME also mentioned some people use the ADC for measurements:
https://forum.rme-audio.de/viewtopic.php?pid=132166#p132166

So basically it is your intended use, if you ask a question like this then of course I expect you don't care about it.

 

[lc155]

I'm not sure what to make of your wording there. I'd certainly care about it if I was using it as a measurement device, but I was mostly interested in its performance as an audio interface.

While it can be used as a measurement device as you say, I don't think RME nor MOTU are marketing these things for that purpose; I'd say that's just a bonus. There will be many people like me who stumble into ASR when purchasing audio stuff just to make sure there's nothing inherently wrong with a potential purchase, so I feel clearing up these things for people who may not understand the exact technicals is beneficial to us all.

 

[bennetng]

So the measurements are presented as is, just let the readers decide. I am pretty sure they have their own mind and judgment.

 

[lc155]

That's what I'm trying to tell you dude, a lot of people cannot interpret the raw data! These numbers are completely meaningless unless you understand the technicals behind them, which most will not; they require interpretation unless you want them to be useless for the majority. Even Amir does basic interpretations of data in his reviews so people can understand the gist of what he is presenting.

I cannot see how this is a hard concept to grasp. We already had someone in this thread saying they couldn't read them.

 

[bennetng]

I don't assume the readers are "clever" or "dumb", in my initial post I only presented the measurements, as someone asked about frequency response.

 

[Blumlein 88]

But does it matter in reality?

I have a different ADC which has response ripples. For its intended use in recording the ripples don't matter. For measuring other gear it would matter a little bit. (one could also develop a correction curve so you could measure other gear with real flat response).

An unintended case where it mattered: I took files and did 8 loopback recordings so you could compare originals to an 8th generation copy. The ripples grow with each generation. I was able to ABX the 8th gen copies due to those ripples. Even then it wasn't bad and very difficult to just barely hear a real difference. I had done the same thing with other gear in the past. Those two pieces of gear had flat response without ripples. I could not hear reliably any difference in those 8th generation copies with flat response.

The ripples don't amount to much for most purposes.

 

[taudier]

That's not what I gathered, he said the SSL2 sucks at <80ohm headphones due to high distortion.

He measured the THD of the SSL 2 (10 ohm output impedance) at 32 ohm load and it was bad, like the focusrite 3d which has an output impedance of 0.35 ohm.
There is also the Steinberg ur22C with a ~90 ohm output impedance which performs equally good at 32 and 300 ohm load, but with a lower power though.
So we have 2 counter examples of the simple relation input/output impedance regarding headphone amps.
The SSL 2 has a monitor output of 1 ohm and could potentially be used for headphone i guess ?
Sorry probably out of Motu m2 topic.

If i understand right the Motu M2 specs, the monitor ouputs are not truely balanced. Is it important ? Maybe measurements with the RCA outputs would be interesting.

 

[Interference]

Thank for the tests!

However, yet another new gen card failing unable to consistently beat the performance of the good old E-MU 0404 that still has a loopback N+D at -95/-98 dB (depending on the input). I am a bit unhappy with the limited headroom of the E-MU (max 3.8x V) but I am having a hard time finding a decent replacement.

 

[lc155]

He measured the THD of the SSL 2 (10 ohm output impedance) at 32 ohm load and it was bad, like the focusrite 3d which has an output impedance of 0.35 ohm.
There is also the Steinberg ur22C with a ~90 ohm output impedance which performs equally good at 32 and 300 ohm load, but with a lower power though.
So we have 2 counter examples of the simple relation input/output impedance regarding headphone amps.
The SSL 2 has a monitor output of 1 ohm and could potentially be used for headphone i guess ?
Sorry probably out of Motu m2 topic.

If i understand right the Motu M2 specs, the monitor ouputs are not truely balanced. Is it important ? Maybe measurements with the RCA outputs would be interesting.

The TRS jack outputs are balanced, the RCA ones are not. It shouldn't matter in reality for short cable runs on a desk.

 

[ehabheikal]

That's what I'm trying to tell you dude, a lot of people cannot interpret the raw data! These numbers are completely meaningless unless you understand the technicals behind them, which most will not; they require interpretation unless you want them to be useless for the majority. Even Amir does basic interpretations of data in his reviews so people can understand the gist of what he is presenting.

I cannot see how this is a hard concept to grasp. We already had someone in this thread saying they couldn't read them.

Yes there are many graphs, i am very well mathematically inclined and still they are very challenging for me since I do not know what to compare with what, but from what i gather from comments here is if we use this as a dac on low gain setting and being measured from its own adc this should be close to the green DACs this forums graphs since the sinad should be like 110db ? Am i close?

 

[bennetng]

Yes there are many graphs, i am very well mathematically inclined and still they are very challenging for me since I do not know what to compare with what, but from what i gather from comments here is if we use this as a dac on low gain setting and being measured from its own adc this should be close to the green DACs this forums graphs since the sinad should be like 110db ? Am i close?

No.
https://www.audiosciencereview.com/...sure-dac-or-amp-performance.14556/post-454298
However, why care so much about SINAD if a 8-generation loopback ABX test revealed audible differences only due to passband ripples, but not due to SINAD?

 

[Evgeniy]

Any tests of mic preamps ?

 

[boXem]

Any tests of mic preamps ?

Well, since it's loopback measurement, they are implicitely tested, but only at their lowest gain. One could imagine setting the output low enough to avoid clipping the input when increasing input gain, but I fear that all that would be shown is amplified output noise. An attenuator would be needed to avois this, mine is broken right now.

 

[Evgeniy]

I bought the M2 for some debug and EOL testing.
Amongst the "cheap" interfaces, it was the one that seemed to have the lowest noise. I didn't really care about distortion since for accurate work, I plan to use an harmonic cancellation software.

Difference between TRS1 & TRS2 - it's broken device or schematic bug ?

 

[boXem]

Difference between TRS1 & TRS2 - it's broken device or schematic bug ?

As written, something was fishy with the first set of measurements, once I re-measured, the two had close performance.

 

[Evgeniy]

How much power M2 use from USB-C / powerbank , when it recorded signal from XLR Mic ports with phantom power ?

Anyone tried use M2 with Android USB Audio Recorder Pro ?

 

[Evgeniy]

- OpAmp TI 88 1AW7 (didn't find anything on Google)

I think, it's TI 88 1AW7 = TI opa1678 , low-cost OpAmp ($0.29 for large quantities).
Because OPA1678 in some case size's marked as AW7, see datasheet.

 

[strab]

I think, it's TI 88 1AW7 = TI opa1678 , low-cost OpAmp ($0.29 for large quantities).
Because OPA1678 in some case size's marked as AW7, see datasheet.

Thanks for that info.

How much power M2 use from USB-C / power bank , when it recorded signal from XLR Mic ports with phantom power?

Anyone tried use M2 with Android USB Audio Recorder Pro ?

I use it with USB Audio Recorder Pro and it works even at 192khz 24bit.
With a USB splitter, with separate power from a power bank, it's very stable.

The power bank I use is a cheap one, very small, 4000mAh and usually I record with a pair of phantom powered Clippy XLR Omni microphones.
Well, I was not able to discharge the battery after 4 hours of recordings. The phone died first.

I think with more expensive microphones, in terms of power (but also $$$), it can last fewer hours.
But such setup is very portable and given the quality of the M2 a bulky field recorder is not needed.
IMHO of course.

 

[Evgeniy]

The power bank I use is a cheap one, very small, 4000mAh and usually I record with a pair of phantom powered Clippy XLR Omni microphones.
Well, I was not able to discharge the battery after 4 hours of recordings.

Thanks !
O, you use CLippy Mic's ? Clippy EM172 ?