Motu 624 Audio Interface Review

[txbdan]

Is it possible to use the Motu 624 for a 2.1 system (as a soundcard/DAC)?

I would like to build my own streamer but struggle to find a good 2.1 DAC. I was thinking to use the Motu and 3 of its outputs for the speakers and sub.

In case it works, would I be able to use the Windows volume control?

I have a MOTU 624 and some of the possibilities are pretty interesting. The mixer has a pretty powerful EQ. You could easily implement different crossovers for the sub and mains outputs. You could even loop the outputs back to an Aux in the DSP mixer and view the FFT of the combination to see how the HP and LP were mixing.


The MOTU Audio Tools that are integrated with the device also offer real time FFT, X-Y, oscilliscope, etc. It's pretty fun to play with. Maybe i'll do a loopback test on mine tonight and see how it compares to these measurements. Is a software generated sine wave good enough for testing?

 

[Blumlein 88]

I have a MOTU 624 and some of the possibilities are pretty interesting. The mixer has a pretty powerful EQ. You could easily implement different crossovers for the sub and mains outputs. You could even loop the outputs back to an Aux in the DSP mixer and view the FFT of the combination to see how the HP and LP were mixing.


The MOTU Audio Tools that are integrated with the device also offer real time FFT, X-Y, oscilliscope, etc. It's pretty fun to play with. Maybe i'll do a loopback test on mine tonight and see how it compares to these measurements. Is a software generated sine wave good enough for testing?

Some more loopbacks on an MOTU 624 would certainly be welcome. Also looks like your first post, so welcome to ASR.

A software generated sinewave should be just fine.

 

[DanGuitarMan]

Chiming in to say I really enjoy using the 624. Flexibility of routing and the web interface are my top two favorite features. It also has AVB audio over ethernet - might lead to some interesting possibilities.

 

[txbdan]

Thanks for the welcome. Long time lurker here.

I don't fully know what i'm doing here, but i plugged a balanced TRS cable from the 624's Main Out 1 into its Analog 1 input. In the DSP routing matrix, i routed the computer output straight to the Main Out. I then used Cubase's TestGenerator utility plugin to create a 1kHz, 0dB, sine wave. In the DSP mixer, all gains are unity except the Main Out which is controlled by the 624's volume knob. I got distortion at 0dB on the Main Out, but it goes away at -1dB. This is at -2dB to be safe.

The FFT jumps around a good bit, around 10dB and it sort of see-saws between the left side of the peak being high and the right side low and vise versa. I kept hitting the pause button to get a shot of something average.

It's also oddly smooth and sort of make it look like the FFT isn't very high resolution. But if i change volume or inject a different waveform, its quite detailed. So maybe the smoothness is real? There's a shot of white noise just to see. I tried at 48kHz and 96kHz device sample rates without any noticeable difference.

Does this make any sense?

Looks like thos produced +/-0.6V? hrm

Edit: I also tried it using Analog Outs instead of the Main Outs to bypass the volume control and it seems to be pretty much the same.

 

[Blumlein 88]

Thanks for the welcome. Long time lurker here.

I don't fully know what i'm doing here, but i plugged a balanced TRS cable from the 624's Main Out 1 into its Analog 1 input. In the DSP routing matrix, i routed the computer output straight to the Main Out. I then used Cubase's TestGenerator utility plugin to create a 1kHz, 0dB, sine wave. In the DSP mixer, all gains are unity except the Main Out which is controlled by the 624's volume knob. I got distortion at 0dB on the Main Out, but it goes away at -1dB. This is at -2dB to be safe.

The FFT jumps around a good bit, around 10dB and it sort of see-saws between the left side of the peak being high and the right side low and vise versa. I kept hitting the pause button to get a shot of something average.

It's also oddly smooth and sort of make it look like the FFT isn't very high resolution. But if i change volume or inject a different waveform, its quite detailed. So maybe the smoothness is real? There's a shot of white noise just to see. I tried at 48kHz and 96kHz device sample rates without any noticeable difference.

Does this make any sense?

View attachment 59633

View attachment 59635

Looks like thos produced +/-0.6V? hrm
View attachment 59639

Edit: I also tried it using Analog Outs instead of the Main Outs to bypass the volume control and it seems to be pretty much the same.

I wonder if there is a setting in the software to set the size of the FFT?

 

[txbdan]

Nope, don't see any settings for that. Maybe it auto sets based on sample rate?

Here's the user guide for the MOTU Audio Tools software:
https://cdn-data.motu.com/downloads/audio/AVB/docs/MOTU Audio Tools User Guide.pdf

 

[HighImpactAV]

I've been using the MOTU 1248 since March of 2015 as my DAC in my home theater. I also have the 624 and the Ultralite AVB. I've also used the 24ao extensively. Some great features I didn't see listed here is automatic sample rate switching with no pops or clicks, multi-client ASIO driver (one program can be sending the output while another receives the input), +20 dBu line output level, individual output trims, two MOTU AVB audio devices can be connected together via AVB to increase channel counts, you can loopback channels internally without using cables, and no pops during on/off when the amps are on.

You can also run multiple playback systems from the MOTU. For example, I was helping run a home theater get-together and Jim Salk was present. We had a Salk system setup and a JTR Speaker system setup. His Salk StreamPlayer wouldn't work, so I just gave him two channels of my 1248 for his system and used two other channels for the JTR system. He used his phone with JRemote to control playback since JRiver Media Center was used to control both systems.

While you can use the PEQ on the DSP, you can't do any crossovers with the MOTU because it is missing low pass filters and delay.

As a little bit of trivia, I was the first to use Thunderbolt output to a DAC at an "audiophile" audio show (RMAF) and the first to use AVB output to a DAC at an audio show (AXPONA). Its nice to see the MOTU products measure better than just about all the other DAC's used at the shows.

I also use the MOTU Audio Tools almost daily and love the ability to quickly look at what is going on in any channel with a the Spectrum Analyzer and Spectrogram. I also use it to test systems during calibration. For example, when using bass management in a Marantz, Denon, or Yamaha pre/pro, the combined bass will clip unless the sub trim is reduced. This is on my worst case scenario clips from How to Train Your Dragon, Olympus has Fallen, and Skyfall. From the manual:

Clip detection You can use the Oscilloscope to detect clipping in a digital audio signal. To do so, enable all criteria (Figure 12), choose Single Sweep from the trigger menu (Figure 12), set the level to 0.999 and click the trigger indicator (Figure 12) to arm it (yellow). As soon as the signal clips, the trigger indicator will turn red, and the display will show the offending clip at the line marking time equals zero.

 

[Matias]

Agreed that this interfaces measures very well and is priced great for such a low recommendation. Good thing is that the data is there for us to make our minds.

 

[txbdan]

^^that's very interesting. This little interface continues to be extremely interesting to learn about and play with. The flexibility of the route matrix and mixer just can't be overstated. The built in reverb and compressors are quite good. I also ran external effects processors through its ins and outs with very little delay. It's a slick piece of gear.

Part of my condundrum at the moment is if i should keep it and use it as a DAC, or sell it because its worth a decent bit and is realistically far more powerful than i need. Particulalry since i'm not as into recording and music production as i was. A new integrated amp with a USB DAC is really all i need and i could basically trade this interface for one.

 

[Matias]

^^that's very interesting. This little interface continues to be extremely interesting to learn about and play with. The flexibility of the route matrix and mixer just can't be overstated. The built in reverb and compressors are quite good. I also ran external effects processors through its ins and outs with very little delay. It's a slick piece of gear.

Part of my condundrum at the moment is if i should keep it and use it as a DAC, or sell it because its worth a decent bit and is realistically far more powerful than i need. Particulalry since i'm not as into recording and music production as i was. A new integrated amp with a USB DAC is really all i need and i could basically trade this interface for one.

Or just add some NCore amplifiers to go with it and you are done.

 

[Matias]

A shame the headphone output is clearly an afterthought. 80mW, really??

 

[360Studios]

Hello, new member here I was wondering if anyone have any experience with Apogee products? I'm curious how MOTU's high end AVB line stacks up with the Symphony or Ensembles as they use the same DAC chips.

I just got the Motu 828ES just two weeks ok and definitely impressed with the features, sound quality and super low latency. I come from mostly a Focusrite background as I've use to own the 1st gen Scarlett 18i20 that I got rid of but I still have the Clarett 8Pre which soon will also get rid off and the Focusrite Forte a similar interface to the Apogee Duet II.

I have have compared the 828ES DAC to my Focusrite Forte and notice some subtle differences. The Forte to my ears after using for 5 years sounds a bit more brighter in the highs with slightly more wider stereo image than the MOTU 828ES. The 828ES does sounds like it has more depth and a beefier low end. I have heard that the 1248 and 16A has more of a 3D sound. Could there be sonic quality differences between the 828ES vs the 1248?

Also does anyone have the the Crosstalk and internal jitter clock specs for the 828ES? For some reason Motu never published those specs.

 

[ehabheikal]

Yeh, I am surprised there is not more outreach to have pro products tested. I thought they would be first inline to get such data as it impacts their day to day work. Distortions and noise accumulate in production scenarios so such metrics are not as academic in playback.

A general observation is that many of these interfaces measure far below audiophile best dacs. The real crap here is that there are many musicians using this for their music, therefore due to these being USED the limit of fidelity in our music sources ( mastered by "crappy" interfaces ) will never match audiophile gear. So even if we do not buy this crap we still suffer from its low quality!
Maybe that is why you need to do more reviews of interfaces, if there are better cheap ones from manufacturers we all will enjoy better mastered music ( from smaller studios)?

 

[HighImpactAV]

A general observation is that many of these interfaces measure far below audiophile best dacs. The real crap here is that there are many musicians using this for their music, therefore due to these being USED the limit of fidelity in our music sources ( mastered by "crappy" interfaces ) will never match audiophile gear. So even if we do not buy this crap we still suffer from its low quality!
Maybe that is why you need to do more reviews of interfaces, if there are better cheap ones from manufacturers we all will enjoy better mastered music ( from smaller studios)?

The pro audio devices are not being tested the way a pro would use them. Many pro audio devices are superior to any "audiophile dac." They are capable of much higher input and output voltages than what is being used for the tests. See the Benchmark Media application note on Balanced vs Unbalanced Analog Interfaces for more information regarding the benefits of high voltage.

 

[Tks]

The pro audio devices are not being tested the way a pro would use them. Many pro audio devices are superior to any "audiophile dac." They are capable of much higher input and output voltages than what is being used for the tests. See the Benchmark Media application note on Balanced vs Unbalanced Analog Interfaces for more information regarding the benefits of high voltage.

I'd wager this to not be true. Unless you mean superior simply = higher output power, then sure, perhaps. Otherwise, I doubt they come close to some of the modern consumer DACs and AMPs.

 

[rvsixer]

Dumb question, I have very little knowledge regarding the recording chain, but are the DAC's in AI's even involved? I would think you go from ADC -> DAW (and then further assume things stay in the digital realm after the AI stage), and the DAC's only used for mixing monitoring? Thanks for shedding any light on this.

 

[Blumlein 88]

Dumb question, I have very little knowledge regarding the recording chain, but are the DAC's in AI's even involved? I would think you go from ADC -> DAW (and then further assume things stay in the digital realm after the AI stage), and the DAC's only used for mixing monitoring? Thanks for shedding any light on this.

That is pretty much true for recording. You might use the DACs for mixing/monitoring as you say, but it is the ADC which sets how accurately the recording is done.

 

[HighImpactAV]

I'd wager this to not be true. Unless you mean superior simply = higher output power, then sure, perhaps. Otherwise, I doubt they come close to some of the modern consumer DACs and AMPs.

Higher voltage means higher SINAD. If tested at 4 Vrms (+14 dBu) and the device can output +19 dBu then you can add 5 to the SINAD score. Some RME DACS can output +24 dBu. It also means you can use a much lower gain amplifier.

Pro DAC's have better crosstalk, lower output impedance, and DC coupling at least for RME/MOTU/Lynx. DC coupling means a flat frequency response to 0 Hz and no phase shift in the bass. Some audiophile DACs, like Digital Amplifier's DAC DAC are also DC coupled, but not too many are.

Regarding output impedance, some "audiophile brands" produce a buffer or preamp buffer that's sole purpose is to lower output impedance. However, the output impedance of the buffer is often still higher than most pro audio DAC's.

 

[HighImpactAV]

Dumb question, I have very little knowledge regarding the recording chain, but are the DAC's in AI's even involved? I would think you go from ADC -> DAW (and then further assume things stay in the digital realm after the AI stage), and the DAC's only used for mixing monitoring? Thanks for shedding any light on this.

In addition to what Blumlein 88 said, there is both digital and analog mastering. Analog mastering might still start with digital audio and then convert to analog and run through multiple analog pieces of equipment before being converted back to digital. Search YouTube for analog mastering.

 

[rvsixer]

@Blumlein 88 - Great, thanks. I noted @ehabheikal saying that DAC's in AI's are causing low quality recordings, and could not reconcile this so asked.