Motu 8A Measurements

[sfabio]

Hello

The RME can be configured for a +4dBu max output level, which of course lowers its noise compraed to its +19dBu mode.
IIRC the Motu output level is around +20dBu, and the output elvel can only be adjusted in the digital domain (a big step back compared to previous models, that the better DAC chip does not compensate for).
Did you compare the RME in +19dBu mode with the motu?

Hello
I think that the switch for +4dBu and +19dBu is only in the new PROfs card (the old is fixed 19dBu?) but anyway I've set the output volume at the maximum possible level

I don't know for the UltraLite, but the 24Ao sure seemed more noisy than many other DACs I have tried, compared to its output level (S/N), and what I heard was not uncorrelated random noise...

Something like this?
MOTU

In any case a +20dBu DAC with a +26dB gain amp and a compression driver is calling for trouble
What you can do is introduce some form of analog volume reduction along the line: either between the amp and dac (a passive reduction like an xlr pad should work given the amp has a buffer), or between the amp and compression driver (lpad, or an autoformer).

I know, I know... You too, don't you? I'm waiting some components to build a cheap multichannel stepped attenuator that can solve a lot of problems, I hope... or I can sell the Motu and buy an Okto dac8...

I guess you could also try removing the buffer on your nc500 build and see if that works well with your DAC

I have the nc500mp and I don't want to break the warranty.
Anyway thanks for replying
Fabio

 

[pos]

Something like this?
MOTU

Yes, exactly the same kind of noise I had on the 24Ao. It goes away during sampling freq change then comes back when synced.
It was still there even with the USB unplugged IIRC.

I know, I know...

Sorry about that.
Nice compression driver by the way!

 

[sfabio]

Sorry about that.
Nice compression driver by the way!

Yes, it's cheap and I like the way it sounds

 

[kartoffelmann]

Could someone please post the noise floor of the 8A in 192 kHz operating mode?

 

[Trdat]

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.

So where do these disperate DACS connect to? I mean you mention when you want a centre speaker its connected to the AVR but where does the AVR connect to?

Also, in this case where you switch from stereo listening to a 3 channel does the motu have saved settings that you switch between?

 

[sfabio]

Yes, exactly the same kind of noise I had on the 24Ao. It goes away during sampling freq change then comes back when synced.
It was still there even with the USB unplugged IIRC.

Sorry about that.
Nice compression driver by the way!

Solved!
Hope this helps!

 

[howard416]

Is the volume control on the front panel for just the "main" stereo output or for all analog outputs simultaneously? Or perhaps does it default to the former and can be programmed to do the latter?

Also, is it the same situation as for the UltraLite mk4?

 

[RayDunzl]

Is the volume control on the front panel for just the "main" stereo output or for all analog outputs simultaneously?

Looks like headphone volume to me.

---

Reads Manual:

Yes, headphone volume.

Channels are controlled by PC.

https://s3.amazonaws.com/motu-www-data/manuals/avb/8A_User_Guide.pdf

"The analog ANALOG OUTS provide line level analog output to any suitable destination, including studio monitors, surround monitors, an analog mixer or any other desired destination. These connectors are balanced (tip/ring/sleeve), but they also accept an unbalanced plug. They are DC-coupled. Control volume from the MOTU Pro Audio Control web app or your host audio software."

 

[somebodyelse]

To expand on RayDunzl's reply they also publish the API used by the web app or host audio software to control things, so it's relatively easy to make your own app to control all outputs from a single control if that's what you want. Assuming the docs are accurate...
https://cdn-data.motu.com/downloads/audio/AVB/docs/MOTU AVB Web API.pdf
Making a handheld remote with something like an ESP32 and a nice rotary encoder for the volume would be an interesting DIY project.

 

[ehabheikal]

I am challenged in reading the above results how well does this compare with motu 624 reviewed here?
How hard/easy to use this as "audiophile" dac? How easy is it to switch inputs from usb to optical or do a workaround maybe to have them both mixed and i operate my own stuff.
Thinking of this mainly to get pure crossover for subs

 

[ehabheikal]

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

View attachment 10545

View attachment 10546
View attachment 10542

ESS9016 DAC + L49724 output op amps
View attachment 10544

Cirrus Logic CS3318, CS5381 ADCs + RC4580 input op amps
View attachment 10543
View attachment 14160

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:

View attachment 10548

0dB 1kHz
View attachment 10549

-6dB
View attachment 10550

-60dB
View attachment 10551

-90.31dB 16 bit
View attachment 10552
View attachment 10553

-90.31dB 24bit - some spuria noted above 10kHz but the level is inconsequentially low.
Nice clean waveform
View attachment 10554
View attachment 10555

-138.46dB
View attachment 10559

Silence - Very low noise floor
View attachment 10561

Jitter
View attachment 10556

IMD SMPTE - Very clean
View attachment 10557
View attachment 10558

FR and Images - Images are suppressed but what are the spuria higher up??
View attachment 10562

Linearity
View attachment 10564


I will update with ADC measurements later. The DAC section generally demonstrates excellent technical performance.

Do these work well with hypex and purify amps. I heard dc coupling could be a problem with them but i do not understand why and what that is.

 

[ehabheikal]

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

View attachment 10545

View attachment 10546
View attachment 10542

ESS9016 DAC + L49724 output op amps
View attachment 10544

Cirrus Logic CS3318, CS5381 ADCs + RC4580 input op amps
View attachment 10543
View attachment 14160

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:

View attachment 10548

0dB 1kHz
View attachment 10549

-6dB
View attachment 10550

-60dB
View attachment 10551

-90.31dB 16 bit
View attachment 10552
View attachment 10553

-90.31dB 24bit - some spuria noted above 10kHz but the level is inconsequentially low.
Nice clean waveform
View attachment 10554
View attachment 10555

-138.46dB
View attachment 10559

Silence - Very low noise floor
View attachment 10561

Jitter
View attachment 10556

IMD SMPTE - Very clean
View attachment 10557
View attachment 10558

FR and Images - Images are suppressed but what are the spuria higher up??
View attachment 10562

Linearity
View attachment 10564


I will update with ADC measurements later. The DAC section generally demonstrates excellent technical performance.

I was told by someone here that motu 624 which should have same engine as this can not do crossovers, can you tell me how you did it?

 

[somebodyelse]

I was told by someone here that motu 624 which should have same engine as this can not do crossovers, can you tell me how you did it?

It's a bit more nuanced than that - it was specifically for subwoofer crossover, and it was the lack of a delay capability that the owner of a 624 said make it unsuitable. The thread starts here for context.

 

[March Audio]

Do these work well with hypex and purify amps. I heard dc coupling could be a problem with them but i do not understand why and what that is.

Yes they do, dc coupling is not an issue, there is no significant dc offset from the dacs.

 

[March Audio]

I was told by someone here that motu 624 which should have same engine as this can not do crossovers, can you tell me how you did it?

It was just used as a multichannel dac/adc. The xo filtering etc was performed by Acourate software in the replay pc.

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

 

[ehabheikal]

Yes they do, dc coupling is not an issue, there is no significant dc offset from the dacs.

Thanx motu it is

 

[18000rpm]

I'm looking for an external DAC to replace the Asus Xonar Essence STX II in my HTPC for better performance and more importantly lower noise.

Will the Motu 8A work as a regular 7.1 surround audio device under Windows 10? And will it support WASAPI and ASIO (for Foobar2000)?

 

[howard416]

To expand on RayDunzl's reply they also publish the API used by the web app or host audio software to control things, so it's relatively easy to make your own app to control all outputs from a single control if that's what you want. Assuming the docs are accurate...
https://cdn-data.motu.com/downloads/audio/AVB/docs/MOTU AVB Web API.pdf
Making a handheld remote with something like an ESP32 and a nice rotary encoder for the volume would be an interesting DIY project.

Yeah, just that there's a huge difference between a tactile volume knob and a screen-based volume control.

Sounds like a lot of work to DIY a rotary encoder...

 

[somebodyelse]

Yeah, just that there's a huge difference between a tactile volume knob and a screen-based volume control.

Sounds like a lot of work to DIY a rotary encoder...

I guess it depends on your skill set, and what you find fun. It's at the easier end of the things people get up to with ESP, Arduino and similar boards. Boards with with integrated LiPo battery charging are widely available for <£10, with or without oled display, so most of the electronics is done for you. The Arduino and NodeMCU programming environments are aimed at beginners, and there are libraries to handle the wifi, http, encoder and button debouncing. You'll probably end up spending more time finding an encoder you like the feel of, and on the physical packaging - maybe something liek the remote for the Quad 66?

 

[Deleted member 4708]

Curios if anyone has measured the headphone out impedance for Motu 8A.