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Motu 8A Measurements

BE718

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#1
I use this Motu 8A as part of a 3 way active DSP speaker crossover. Its a cost effective (about $800 https://www.amazon.com/MOTU-9360-8A/dp/B01MRUNV1D ) 8 in 8 out ADC/DAC interface aimed at studio work. It has USB 3, Thunderbolt, Ethernet AVB and optical connectivity. Audio connections are balanced/single ended TRS jacks. A headphone jack and volume control are situated on the front panel. Power comes from an external SMPS wall wart.

Casework is robust high quality aluminium shell in two halves. A small but clear LCD display shows channel level and other information.

More info here: http://motu.com/products/avb/8a

m1.jpg


m2.jpg

20170605_191422.jpg


ESS9016 DAC + L49724 output op amps
20170605_191532.jpg


Cirrus Logic CS3318, CS5381 ADCs + RC4580 input op amps
20170605_191516.jpg

IMG_20180723_160524.jpg


Measurements

Im going to look at the DAC in this part and update with ADC tests later. In Out is 24bit up to 192kHz sample rates. Manufacturer specs:

upload_2018-2-11_14-45-6.png


0dB 1kHz
upload_2018-2-11_14-52-1.png


-6dB
upload_2018-2-11_14-53-22.png


-60dB
upload_2018-2-11_14-56-20.png


-90.31dB 16 bit
upload_2018-2-11_14-59-41.png

upload_2018-2-11_15-0-15.png


-90.31dB 24bit - some spuria noted above 10kHz but the level is inconsequentially low.
Nice clean waveform
upload_2018-2-11_15-2-31.png

upload_2018-2-11_15-3-47.png


-138.46dB
upload_2018-2-11_15-10-55.png


Silence - Very low noise floor
upload_2018-2-11_15-13-20.png


Jitter
upload_2018-2-11_15-5-46.png


IMD SMPTE - Very clean
upload_2018-2-11_15-7-36.png

upload_2018-2-11_15-8-21.png


FR and Images - Images are suppressed but what are the spuria higher up??
upload_2018-2-11_15-29-58.png


Linearity
upload_2018-2-11_15-40-36.png



I will update with ADC measurements later. The DAC section generally demonstrates excellent technical performance.
 
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#2
Nice work. I looked at the motu ultra lite mk4 not too long ago.

Just curious, does the QA401 software allow you to overlay and compare results from previous measurements?
 

BE718

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#3
Nice work. I looked at the motu ultra lite mk4 not too long ago.

Just curious, does the QA401 software allow you to overlay and compare results from previous measurements?
I dont think the the Ultralite shares the same A/D D/A chips as 8A so may perform quite differently.

Unfortunately the QA software doesnt allow you to simply overlay previous data, however you can export the measurement into .csv and use excel to create composite plots.
 
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#4
I dont think the the Ultralite shares the same A/D D/A chips as 8A so may perform quite differently.

Unfortunately the QA software doesnt allow you to simply overlay previous data, however you can export the measurement into .csv and use excel to create composite plots.
I came across the Motu looking for lower cost alternative A/D converters to RME stuff. The Ultra lite MK4 definitely uses different chips. Not sure what it actually uses. I'll have to take a closer look at both.

The QA401 is a tool I keep on circling back to. I find the price to functionality attractive. This would be a useful tool for me to test my diy headphone amp builds. It is too bad the software is not more flexible.
 

BE718

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#6
The softwate is pretty simplistic and limited. It will alow you to take a snapshot which remains on screen and continue measuring, but not reload a measurement taken previously. I suppose itsca reflection of the price.
 
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#7
The softwate is pretty simplistic and limited. It will alow you to take a snapshot which remains on screen and continue measuring, but not reload a measurement taken previously. I suppose itsca reflection of the price.
It is mostly the price to features that attracted me to the QA 401. I'll have to do a bit more research on this before pulling the trigger. It looks like the asio driver is in progress.
https://quantasylum.com/blogs/news/asio-and-hypermiling-thd

The measurements on the motu 8a dac is fairly impressive. Especially the linearity. It will be interesting to see how some of your future dac measurements compare.
 

BE718

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#8
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soundArgument

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#9
@BE718, thanks for posting these measurements! I'm curious about using the Motu 8A for the same purpose as you--as part of an active crossover.

One question about that: do you use the Motu 8A alone to do D/A duties, or do you use it in conjunction with other converters? If you do the latter, how do you manage variations in latency among different converters?
 

BE718

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#10
@BE718, thanks for posting these measurements! I'm curious about using the Motu 8A for the same purpose as you--as part of an active crossover.

One question about that: do you use the Motu 8A alone to do D/A duties, or do you use it in conjunction with other converters? If you do the latter, how do you manage variations in latency among different converters?
Im only currently using the 8 channels, 3 each for the left right and 2 for subs. My centre speaker for theatre duties is actuall driven by the avr.

I use Acourate software to perform the XO duties. Time correction can be performed on any of the outputs so it shouldnt be a problem to use multiple disperate dacs.
 

pos

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#11
@BE718, thank you for these measurements!
I am considering buying a motu 24 Ao (same dacs as the 8A) for a similar purpose as yours (active crossover) on a dedicated linux machine (its is class compliant and reported to work!).
As I will be using fragile compression drivers I would like to be sure it is a reliable device.
Did you ever encounter problems or instabilities with your motu (on sampling frequency change, etc.), or pop/noises (even faint ones) when pluging/unpluging the device, or turning it on or off with the button or the power plug?...
 

dwalme

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#12
@BE718, thank you for these measurements!
I am considering buying a motu 24 Ao (same dacs as the 8A) for a similar purpose as yours (active crossover) on a dedicated linux machine (its is class compliant and reported to work!).
As I will be using fragile compression drivers I would like to be sure it is a reliable device.
Did you ever encounter problems or instabilities with your motu (on sampling frequency change, etc.), or pop/noises (even faint ones) when pluging/unpluging the device, or turning it on or off with the button or the power plug?...
I used a Motu 24A0 to run on my JTR 212HTR speakers 3-way active with Audiolense XO. The compression driver is 118db BMS coaxial compression driver.

I no longer have that setup as I had no good way to use sources other than Jriver where I was running the convolution engine. (The audio delay was significant with no way to delay video to match - audio only setup would not have been a problem)

No pops or noises at all. It should work very well for you with regard to what you posted as your concerns.
 

Blumlein 88

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#13
So are you still going to do ADC measurements? If it comes close to matching the DAC, the Motu might be a very useful measuring tool itself.
 

BE718

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#14
@BE718, thank you for these measurements!
I am considering buying a motu 24 Ao (same dacs as the 8A) for a similar purpose as yours (active crossover) on a dedicated linux machine (its is class compliant and reported to work!).
As I will be using fragile compression drivers I would like to be sure it is a reliable device.
Did you ever encounter problems or instabilities with your motu (on sampling frequency change, etc.), or pop/noises (even faint ones) when pluging/unpluging the device, or turning it on or off with the button or the power plug?...
Hi

Its well behaved, no nasty noises. TherE can be a slight click ay switch off but nothing that should break anything.
 

RayDunzl

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#16
Its well behaved, no nasty noises.
I looked for detail on the Motu, but didn't find.

Probably does something like Benchmark:

upload_2018-3-23_18-36-12.png


My DAC2 might have made noise on a non-PCM stream from the TV when messing with the settings, otherwise, also well behaved, no nasty noises.
 
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#17
I use this Motu 8A as part of a 3 way active DSP speaker crossover. Its a cost effective (about $800 https://www.amazon.com/MOTU-9360-8A/dp/B01MRUNV1D ) 8 in 8 out ADC/DAC interface aimed at studio work. It has USB 3, Thunderbolt, Ethernet AVB and optical connectivity. Audio connections are balanced/single ended TRS jacks. A headphone jack and volume control are situated on the front panel. Power comes from an external SMPS wall wart.

With what monitors and amplifier(s) do you use the Motu8A? And do you have any thoughts on how the Motu compares to other active crossover DSPs such as the MiniDSP or others?

And by the way, did you ever get any data on the Motu's ADC? Thanks.
 

BE718

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#18

With what monitors and amplifier(s) do you use the Motu8A? And do you have any thoughts on how the Motu compares to other active crossover DSPs such as the MiniDSP or others?

And by the way, did you ever get any data on the Motu's ADC? Thanks.




The Motu is used with my own active speaker design. The amps are Hypex modules. Details can be found here.

https://audiosciencereview.com/forum/index.php?threads/3-way-dsp-xo.991/

The Motu is obviously just a DAC and ADC, its not performing any of the DSP filtering work. For that I use Acourate software.

https://www.audiovero.de/en/acourate.php

The overall solution is significantly superior to miniDSP, although miniDSP are a good starting point for dsp crossovers, simple to implement and good value for money.

Some measurements of a miniDSP 2x4HD here

https://audiosciencereview.com/forum/index.php?threads/measurements-of-minidsp-2x4hd.2459/

I will try and do the ADC measurements this week.

Hope that helps :)
 
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#19
Thank you that helps clarify your step up. Very helpful. Had you considered other audio interfaces in similar price range to the Motu, such as Apogee, Apollo, or Focusrite?

I think RME may be a bit more expensive.
 

BE718

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#20
Considered yes, but from memory the Motu offered best performance on paper, was the right price and readily locally available. Luckily my "punt" payed off and its performance is excellent.

I think @Blumlein 88 has some of those interfaces he may be able to test in detail.
 
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