Motu M4 Audio Interface Review

[AnalogSteph]

@bennetng Your Google-Fu must be better than mine, I tried to find a proper datasheet for the ES9016 and couldn't!

Anyway, if periodic ripple is within +/-0.003 dB even in the sharp rolloff filter, that's not a major concern (even if it's not a world-beater). The DAC side is rarely too problematic in this regard.

 

[bennetng]

@bennetng Your Google-Fu must be better than mine, I tried to find a proper datasheet for the ES9016 and couldn't!

Anyway, if periodic ripple is within +/-0.003 dB even in the sharp rolloff filter, that's not a major concern (even if it's not a world-beater). The DAC side is rarely too problematic in this regard.

I can't find the ES9016 datasheet as well and it is from ES9012/ES9018 (the same file). Just want to point out the filters are proportional to sample rate, which applies to AKM and others as well. In the case of newer Sabres the "Brickwall" filter with full attenuation at fs/2 has poorer stoppand attenuation, so there is a price to pay for this filter.

 

[zandm7]

No. The filter works in the same way in 44.1k and 48k, the response is proportional to the sample rate. 0.5fs means 0.5 * sample rate, so 22.05k for 44k sample rate and 24k for 48k sample rate.

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OK cool lol, I guess I'll just stick with everything at 44.1 kHz then. Thanks!

 

[trl]

So power level is more or less the same. The good news is that output impedance is quite low so should not change the tonality of the headphone.

Seems that the headamp is based on OPA1688 op-amp, so probably the power rails are too low to get a more juice out of it: https://prosound.ixbt.com/interfaces/motu/m4/image7.jpg.

 

[Thorskin]

I have been looking forward to this review, thanks. It looks like a great device.
Do you guys think it would be a downgrade to sell and replace my Modi3/Magni3+ with one of these?
I could really use an ADC and having an all in one device would be preferable but not if the Magni3+ performs much better.
My main headphones are LCD2C and HD650s and occasionally some Grado sr60s or IEMs.

 

[trl]

You can not compare Magni 3+ with the built-in headamp of the M4, so you will need to keep the Magni 3+ and find a proper cable to interconnect these two devices...or simply keep them all 3.

 

[JeffGB]

I received my Motu M4 yesterday, after an 8-week wait. It works perfectly. I was a bit surprised that the windows 10 settings only included 24 bit and not 32 bit. I wanted the 32-bit option for the added perfection of the volume control but I realize now that the digital volume control is likely not using the windows settings. It should be using the 32-bit internal volume control of the ESS DAC chip, so should be ok. I'm driving a Crown XLS 1500 with the balanced output of the M4. My noise problems are now gone. I have to set the Crown level controls at approximately 1 pm to keep the volume control of the M4 from being at its very beginning.

I think I will attempt to take the chassis apart in a day or two, just for research of course . I'll take a few images as well, to post. So far it's been a seamless experience. I loaded the driver before I received my device, so when I got it home I simply plugged it into my USB 3 powered hub and it was picked up as the primary sound card. I love the meters . It works just fine. No clicks or pops with any material I've played from cd rips to youtube. No audible sounds from the DAC when changing bit depth etc, like some earlier DACS.

Ok, please allow a couple of subjective sound comments. It's clean and quiet, as expected. It's an interesting variation compared to my other DAC's. The bass is tight and clean, with good power and impact. The soundstage appears a bit more open than I am used to. Certain types of music, like loud classic rock, are handled very well. An electric guitar can sound like it's less lost in the mix, as are other small details. Like you are listening and something is standing out in the music that you had not noticed before, but was no longer lost in the overall mix. I know. It sounds ridiculous. It's like some instruments that you are following disappear into the other instruments as they build up and now they can be followed through. This is comparing a Creative G6 and Teac ud301, both of which should be audibly transparent. Ok, enough. I've clearly cemented myself in the subjectivity nutjob category that buys things based on Amir's tests and recommendations but still hears differences . This is the first ESS DAC I have listened to. It does seem to have a slightly different character.

I'll hopefully be back in a few days with some images of it's internal build.

 

[JeffGB]

Interestingly enough, I just tried single-ended connections to the Crown from the MOTU. I have been struggling with noise picked up between my Schiit Heresy and the Crown XLS for months. I tried every trick for ground loops and cable types that I could. Nothing stopped the bursts of noise and whining caused by (I think) my computer/wifi/cell phone. I also live on the top floor of a high rise apartment building, so lots of wiring and antenna's on the roof to spread the noise. It wasn't strictly ground loop noise because I could unhook the DAC from the Heresy and the noise was still there. It appeared to be literally the Heresy that was picking it up.

With the MOTU hooked up using the balanced connections, the noise was completely gone but the strange thing was when the MOTU was connected by the single-ended connections, the noise was also absent. I guess this means that the Schiit Heresy works as an antenna to a point when connected to a power amplifier. I should add that the noise was dramatically lower with the MOTU single-ended than the Heresy when driving several different amplifiers, including a Sansui AU-X701 which has a completely balanced power amplifier from input to output. I also have an ADCOM GFA-5500 which is an all MOSFET Nelson Pass design. Even the input stages were power MOSFETs. It has only single-ended RCA inputs that had noise when trying the Heresy/G6 combo so now I'm hopeful it may work well with the MOTU.

My question, if anyone has an answer, is what is causing the Heresy to be so bad with RFI/EMI noise? Is it that the chassis has slots for cooling? The MOTU seems very well shielded. It has a complete metal shell and even the knobs are metal, which might block some of the RFI coming in through the holes for the controls? I have no idea. I just know the MOTU is far less susceptible to picking up external EMI etc than is the Schiit Heresy. This is something that I wish Amir could test for. I would still prefer to have an analog volume control in a high-level stage to drive my amplifiers, rather than rely on the digital volume control of the MOTU, but it seems pretty decent so far.

Do you think it is possible to measure the susceptibility to EMI/RFI of a device in practical terms? I guess you would have to build a box that was shielded and had an emitter of EMI/RFI inside with the device under test and then measure that vs other devices under the same conditions? Anyway, not suggesting anyone do that, just thinking about it .

Does anyone have any ideas about the Schiit Heresy? Is it the trace length going to the headphone jack and back to the RCA outputs that are picking up the noise? The Heresy is a great headphone amp, I just would like its abilities to be able to be enjoyed through speakers .

 

[trl]

what is causing the Heresy to be so bad with RFI/EMI noise?

Are you 110% sure this is RIF/EMI noise?

I've seen many cases with such noises when the DAC and amp were having isolated power supplies and the internal audio ground was disconnected from the outer case and connecting the outer case to the Earth or to computer's GND/case might help.

L.E.: Sometimes this is also happening when one device from the audio chain (DAC) has the audio ground tied up to outer case ground and the other device don't (the amp).

 

[JeffGB]

I have removed the DAC entirely from the circuit and the noise remained. Just the Heresy connected to the power amplifier. The amplifier with the Heresy removed is quiet. The amplifier with the DAC connected directly to it is quiet. If I connect the Heresy the noise is there and it changes as I move the Heresy around on my desktop. I tried heavy copper lines connected between the Heresy chassis and the Crown amplifier. When that was done it was a bit quieter but the noise was still there. The noise comes in bursts along with a steady-state whine. There is no hum.

As far as I can tell it is the Heresy picking up RFI/EMI when cables connect it to another device. There is no noise when used with headphones, so the Heresy is doing its job as far as that is concerned. The Heresy has a two-wire connection to AC afaik. I've tried several DAC's with the Heresy. Some are USB powered and some have separate power supplies. Nothing has removed the noise with the Heresy. I would still like to use the Heresy for my volume control at my desk.

 

[bequietjk]

Has anyone A/B'd the balanced vs unbalanced output through an external headphone amp? Got my M2 here and wondering how the TRS would sound going into my 789 ^_^. Amazon order pending...

 

[AnalogSteph]

In general, using the integrated headphone output would be my preferred method of connecting an external "afterburner" with unbalanced inputs (e.g. Atom, L30, Magni Heresy). It's not a significant step down from the main line-out for this purpose.

That said:
1. The 789 comes with a fairly beefy SMPS power brick. Keep shield resistance on the TRS --> 2x RCA cabling down to minimize hum intrusion from power supply leakage currents.
2. If you are already using the 789's balanced inputs for something else, you could create a ground loop that way.

BTW, here's a general reminder that the M2/M4 use AKM ADCs, and that we don't know how many of these MOTU may have stockpiled.

 

[trl]

BTW, here's a general reminder that the M2/M4 use AKM ADCs, and that we don't know how many of these MOTU may have stockpiled.

Are you referring to https://www.prosoundnetwork.com/business/akm-factory-fire-shakes-up-pro-audio-industry?

Thomann was able to ship me the M4 couple of days ago, after I saw that ETA moved to 12-15 weeks and I told them that I want to cancel my entire order. They probably received few from the "old stock". Now I'm stuck wth a Clarett 2Pre I just bought and the M4 in on it's way too.

 

[lc155]

Had my M4 for a few days now, managed to nab one from a store on eBay with a voucher code, so I got it for the price of the M2 - seemed like a no-brainer to get the higher end version then.

Don't have a current use for the M4 over the M2, but the 3/4 line outs for running an external amp is a nice option to have if I ever feel the need to use it considering the M4 barely adds any additional bulk.

I thought the more crushed level meters would be a downside over the M2, but they're still fairly readable at a distance and the only one that really matters (mic input levels) you generally only need to set once to avoid clipping.

 

[phoenixdogfan]

As an A to D converter, is the USB 3 its digital output? If so, how can it be the power input and the digital output?

 

[somebodyelse]

As an A to D converter, is the USB 3 its digital output? If so, how can it be the power input and the digital output?

The USB Audio Class is bidirectional, so the USB port is both digital input and output at the same time.

 

[AnalogSteph]

As an A to D converter, is the USB 3 its digital output? If so, how can it be the power input and the digital output?

Weird question. How do you think USB keyboards and mice work?

 

[AllanDavidson]

I just wanna share with you guys that tomorrow is my 5th Fu**ing Month waiting for the MOTU M4 I purchased on Guitar Center.

 

[Blumlein 88]

I just wanna share with you guys that tomorrow is my 5th Fu**ing Month waiting for the MOTU M4 I purchased on Guitar Center.

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That is not good. Appears they are back ordered or have extensive wait times everywhere however.

 

[JeffGB]

Wow, that's a long time. I'm in Vancouver Canada and I ordered one from Long & Mcquade on Sept 6 and I've had it for a couple of weeks now. I've been checking other stores in the US like B&H and they seem to have new stock. Perhaps a call to Guitar Center would be in order.