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MOTU M2 loopback measurements

lc155

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For cycling the knob to get the 10dB lower noise (I presume you mean the big monitor knob?) does this have to be done on every power cycle or was it a once and done job? Seems a bit weird if it needs to be done every time but I don't know much about this stuff clearly!
 
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boXem

boXem

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For cycling the knob to get the 10dB lower noise (I presume you mean the big monitor knob?) does this have to be done on every power cycle or was it a once and done job? Seems a bit weird if it needs to be done every time but I don't know much about this stuff clearly!
Once and done. I didn't really get what happened.
Another thing to mention is that I finalized the measurements with the ASIO4All driver, the MOTU driver having a tendency to trash my 32 averages just before they finish... Before somebody asks, buffer was at the same size for both.
 

lc155

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Once and done. I didn't really get what happened.
Another thing to mention is that I finalized the measurements with the ASIO4All driver, the MOTU driver having a tendency to trash my 32 averages just before they finish... Before somebody asks, buffer was at the same size for both.

Ah okay, yeah I've heard that it is good practice to cycle the knobs when you get a new amp or whatever for things like this. Funny to see it in practice though despite hearing about ita few times over the years.
 
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strab

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Hope that this is useful.
Things that I found on my MOTU M-2:

- AD AKM AK5552VN
- DA ESS ES9018S
- OpAmp TI 88 1AW7 (didn't find anything on Google)
- Microcontroller processor XMOS U11680C20

Started enjoying this forum today, so literally a noob here.
When you measure with the loopback you mean the TRS output - TRS input via TRS cable?
Because in this case if the DA conversion is better than AD you are limited by this one, which is recording.
Wrong?
 

ofrappier

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Hi,

Do you use the 24 bits drivers ? and a generator in 24 bits dither ? ( not 16 bits? ...)

Capture d’écran 2020-05-09 à 22.02.37.png
 
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boXem

boXem

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Hope that this is useful.
Things that I found on my MOTU M-2:

- AD AKM AK5552VN
- DA ESS ES9018S
- OpAmp TI 88 1AW7 (didn't find anything on Google)
- Microcontroller processor XMOS U11680C20

Started enjoying this forum today, so literally a noob here.
When you measure with the loopback you mean the TRS output - TRS input via TRS cable?
Because in this case if the DA conversion is better than AD you are limited by this one, which is recording.
Wrong?
Right
Just for fun, I inserted a 30dB attenuator, making the ADC to work in it's comfort zone, if I remember well the THD at 0DBFS was then - 107 dB.
 

sergeauckland

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What that last spectrum shows is that all noise and distortion products are below 110dB and therefore completely inconsequential. A very fine result. It doesn't show frequency response, but assuming that's OK, and there's no reason to suppose it isn't, then completely satisfactory in every respect.

S
 

strab

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That's almost in line with MOTU specifications on their website.

@ofrappier used a 8A for ADC and the specs are:

2020-05-16 131405.png


The specs of the M2 are:
2020-05-16 133044.png


I know that the specs reported on the product website are not comparable with the details of the test you guys make here in this forum.
But kudos to MOTU for beign "honest" enough.
 

bennetng

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What that last spectrum shows is that all noise and distortion products are below 110dB and therefore completely inconsequential. A very fine result. It doesn't show frequency response, but assuming that's OK, and there's no reason to suppose it isn't, then completely satisfactory in every respect.

S
There would be some ripples in loopback mode as it uses an AKM ADC:
https://prosound.ixbt.com/interfaces/motu/m4/2444.shtml

RME ADI-2 series also use AKM ADC, but the ripples are reduced by the FPGA anti-ripple filter:
https://www.forum.rme-audio.de/viewtopic.php?pid=132179#p132179

However, even without the FPGA filter, if ADC is operated at a higher rate, then the ripples would be reduced as well.
https://velvetsound.akm.com/content.../audio-adc/ak5554vn/ak5554vn-en-datasheet.pdf

TI and Cirrus for example have ADCs with lower ripples in 44/48k, at least invisible in RMAA's default zoom scale.
 

lc155

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There would be some ripples in loopback mode as it uses an AKM ADC:
https://prosound.ixbt.com/interfaces/motu/m4/2444.shtml

RME ADI-2 series also use AKM ADC, but the ripples are reduced by the FPGA anti-ripple filter:
https://www.forum.rme-audio.de/viewtopic.php?pid=132179#p132179

However, even without the FPGA filter, if ADC is operated at a higher rate, then the ripples would be reduced as well.
https://velvetsound.akm.com/content.../audio-adc/ak5554vn/ak5554vn-en-datasheet.pdf

TI and Cirrus for example have ADCs with lower ripples in 44/48k, at least invisible in RMAA's default zoom scale.

But does it matter in reality?
 
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