Motu M4 Audio Interface Review

[trl]

I am not aware of TRS mono plugs, please have a read here: https://www.sweetwater.com/sweetcare/articles/whats-the-difference-between-ts-and-trs-cables/.

I do have the M4 and I don't remember having issues with the TRS front inputs. I've also wrote a teardown article here: https://www.audiosciencereview.com/...analysis-and-few-in-house-measurements.17819/.

Also, Motu states that front jacks are TRS: https://cdn-data.motu.com/manuals/usb-c-audio/M_Series_User_Guide.pdf at page 25, so I am not sure I fully understand the issue you're facing with this interface. It has similar front jacks like the Focusrite and should work the same way.

 

[Damian]

I am not aware of TRS mono plugs, please have a read here: https://www.sweetwater.com/sweetcare/articles/whats-the-difference-between-ts-and-trs-cables/.

I do have the M4 and I don't remember having issues with the TRS front inputs. I've also wrote a teardown article here: https://www.audiosciencereview.com/...analysis-and-few-in-house-measurements.17819/.

Also, Motu states that front jacks are TRS: https://cdn-data.motu.com/manuals/usb-c-audio/M_Series_User_Guide.pdf at page 25, so I am not sure I fully understand the issue you're facing with this interface. It has similar front jacks like the Focusrite and should work the same way.

The way it works.. the front TRS are mono balanced, and if you use the two together they can be stereo. On the back also two inputs TRS balanced, which together give stereo. Hope is clear as it took some time for me to get it!

 

[AllanDavidson]

I am not aware of TRS mono plugs, please have a read here: https://www.sweetwater.com/sweetcare/articles/whats-the-difference-between-ts-and-trs-cables/.

I do have the M4 and I don't remember having issues with the TRS front inputs. I've also wrote a teardown article here: https://www.audiosciencereview.com/...analysis-and-few-in-house-measurements.17819/.

Also, Motu states that front jacks are TRS: https://cdn-data.motu.com/manuals/usb-c-audio/M_Series_User_Guide.pdf at page 25, so I am not sure I fully understand the issue you're facing with this interface. It has similar front jacks like the Focusrite and should work the same way.

TRS can be either Balanced Mono (Default) or Unbalanced Stereo (not very used)

Motu and Focusrite, like every other interface out there, only captures a single mono signal from each connection.

The only exception is the Headphone out, which usually is 3.5mm TRRS or TRS Stereo

 

[Damian]

Those are also TRS balanced mono.

Yes, but can be used as L and R. I just need to get a cable from TRS stereo to dual TRS mono balanced.

 

[AllanDavidson]

Hello guys,

I just got a Motu M4 coming from a Focusrite 2i2 3rd Gen. I do understand the front inputs are TRS mono and not stereo? I cannot make it work as stereo.

The front inputs are TRS Balanced Mono, but maybe you can set it up to Unbalanced Stereo.

And secondly and more important, while driving my Adam T8V, the focusrite seems to have more power than the Motu, which is a bit annoying.. any ideas? I can barely loud enough when I crank the volume all up playing music from windows (yes the windows master volume is 100).

The Line Outs 1/2 are controlled by the internal monitoring, the Line Outs 3/4 are full volume (DAC out)

 

[Damian]

The front inputs are TRS Balanced Mono, but maybe you can set it up to Unbalanced Stereo.



The Line Outs 1/2 are controlled by the internal monitoring, the Line Outs 3/4 are full volume (DAC out)

For what everyone is saying and as per my research, there is no way to configure the front input TRS as stereo. Moreover, if I look at the LCD screen, the inputs are labeled as mono, so there are in total 4 mono inputs. 1-2 together can be stereo, and 3-4 together can be stereo. Hope it makes sense for others looking for the same as well. I guess this is the meaning of a 4x4, 4 mono inputs, and 4 mono outputs as channels (as in the back they do repeat in RCA and TRS).

 

[trl]

The way it works.. the front TRS are mono balanced, and if you use the two together they can be stereo. On the back also two inputs TRS balanced, which together give stereo. Hope is clear as it took some time for me to get it!

This is the normal way for an audio interface to operate. TRS is a stereo jack plug that works as mono by default when used in balanced audio systems, this is why I feel is a pleonasm when calling a TRS plug as being mono balanced.

Also, left and right are relative to what you need to do, but usually these inputs are named Analogue Input #1 and Analogue Input #2 (corresponding to Track #1 and Track #2). Left and right channels are to be done later via post-production, if needed, so the term "stereo" is something that I find it confusing in this context.

If you need to record stereo with two mics, then you should use both front XLR analogue Inputs. If you need to record a guitar, then you should use only one TRS analogue input, then mix the recording to both channels to make it mono on two channels.

 

[Erosenbe]

In1/in2 accept xlr, trs, or ts (inst). They are paired L-R on the monitor out. Max dbu corresponding to 0dbFS is somewhat lower in front than in3/in4 on the back. Most interfaces work like this. So if you have a signal at nominally line level and want to maximize SNR or headroom you are probably best off connecting in the back.

 

[Damian]

I still find the output level with the volume at max used as a DAC to be lower than the focusrite... the headphone output on the other hand can drive the HD6XX without any problems.

 

[trl]

I still find the output level with the volume at max used as a DAC to be lower than the focusrite...

This is not important, what it matters is that both audio interfaces are able to output the correct balanced line level voltage of 4 V RMS. If one is able to output 5 V and another one can output let's say 4.3 V, when potentiometer is maxed out, this is a non-issue.

Feel free to check again both reviews for 2i2 Gen3 and M4, for a better understanding of how Amir measured them and how the results should be interpreted. Also, maxing out the volume pot. is not recommended, as the input stage of the connected amplifier might be overdriven and start to distort.

I suggest you to create a new thread and state there your issues, so ASR community could help you out, but don't forget to include the following details:
- accurate description of all equipment from your "under test" audio chain, including all analogue cables too;
- measurements done on all balanced cables (to be sure there is no short-circuit on none of them and there is near zero Ohms resistance for both hot wires and for the GND too);
- measurement of the output voltage done with a multimeter between the (+) & (-) of the TRS cables for both interfaces, with volume knobs to the max. or immediately before clipping (preferable to start with -1 dB sinewave and move to 0 dB sinewave only if DAC output is not distorting);
- drivers versions used;
- test files used.

 

[oversorrow]

Thanks for the test. I‘m a newbie in this professional realm, I just want to know that how M4 can provide 60dB of gain while the preamp chip's gain range is 42dB (-8dB to +34dB, listed on the manufacturer's website).
Is there another way to increase the gain? Does anyone know how that works? Thanks.
THAT Corporation 626x 2-CH Digitally-Controlled Mic Preamp IC

 

[Blumlein 88]

Thanks for the test. I‘m a newbie in this professional realm, I just want to know that how M4 can provide 60dB of gain while the preamp chip's gain range is 42dB (-8dB to +34dB, listed on the manufacturer's website).
Is there another way to increase the gain? Does anyone know how that works? Thanks.
THAT Corporation 626x 2-CH Digitally-Controlled Mic Preamp IC

From the tear down thread on this M4:

Analogue inputs from the front panel are buffered by couple of OPA1678 op amps and the gain is adjusted by the dedicated THS4522 and THAT6263 chips. I am guessing that the first one acts as an input buffer and is having a fixed gain, while the second is changing the gain in 3dB, per manufacturer datasheet, although in real-life M4 mic inputs are fine adjusted by 1dB and not by 3dB. Perhaps someone else could jump in here with some thoughts about how the above two chips might be used inside the M2 & M4.

So they probably use the gain of the THS4522 chip with the microphone pre chip.
https://www.ti.com/lit/ds/symlink/ths4522.pdf

 

[trl]

Thanks for the reply @Blumlein 88. Maybe the two THAT chips are indeed serialised, maybe the input buffer opamp is not unity gain after all, I can't tell that without doing measurements in real-time with an audio source connected to the analogue inputs (which I don't want to do due to the high risk to make short-circuit on the PCB).

What's important is that the M4 has a more than enough +60 dB gain (works with SM7B too) and an analogue Line-input on the back that bypasses the input buffers from the mics (great for doing 5 W /8 Ohms measurements on amplifiers).

 

[Kane1972]

The new Audient interfaces have improved the specs.,wish the ID14 line inputs bypassed the preamps. The ID44 does but that’s too pricey for me right now. Tascam 208i looks great at the price.

 

[trl]

The ID44 does

Man, you're right:

"Direct Access to ADC The Insert return connection on the iD44 is a electronically balanced input stage that directly drives the analogue to digital converter for that channel. As such, this is a great place to input signals directly to the ADC, bypassing the preamplifiers and minimising any colouration of the signal. This makes it useful to patch in external microphone pre-amplifiers without adding additional colouration or noise. It is also handy for using the iD44’s outputs to drive external effects before returning them into your DAW using the insert returns", source: https://d9w4fhj63j193.cloudfront.net/2021/iD44/English/Audient iD44 Manual V2.pdf.

It would be nice to see this baby tested on ASR, especially this dedicated analogue input.

However, spec'd data seem better on the Motu M4 vs. the Audient ID44, based on their own datasheets. Not sure real-life measurements will be different or not, hope we'll see this interface measured here.

 

[AllanDavidson]

Man, you're right:

"Direct Access to ADC The Insert return connection on the iD44 is a electronically balanced input stage that directly drives the analogue to digital converter for that channel. As such, this is a great place to input signals directly to the ADC, bypassing the preamplifiers and minimising any colouration of the signal. This makes it useful to patch in external microphone pre-amplifiers without adding additional colouration or noise. It is also handy for using the iD44’s outputs to drive external effects before returning them into your DAW using the insert returns", source: https://d9w4fhj63j193.cloudfront.net/2021/iD44/English/Audient iD44 Manual V2.pdf.

It would be nice to see this baby tested on ASR, especially this dedicated analogue input.

However, spec'd data seem better on the Motu M4 vs. the Audient ID44, based on their own datasheets. Not sure real-life measurements will be different or not, hope we'll see this interface measured here.

This is what RCA connectors are intended for, this is why they exist, it means "no amplification involved" while on output (or input as well, when dealing with a capture device). They are wired straight to converters, without any amplification or treatment. They allow your video game/VCR/DVD/PC/whatever send raw analog audio to your External Amp/Stereo, so it can be amplified there.

RCA inputs on capture devices go straight to the ADC, and also straight from the DAC if on output. Except on amps, of course, where RCA inputs are amplified before going to speakers/headphones.

On the other hand, T*S and XLR connectors mean "amplification involved", the signal being amplificated by the device after the input, or before the output.



Ps: Since we almost always use devices with built-in microphones, in 99.9% of the cases someone interact with audio connections is to output audio, leading to a society full of devices with RCA outputs, but almost no RCA inputs.

 

[Kane1972]

TS, TRS and XLR do not mean "amplification involved". Pro line inputs are on TRS or XLR and they bypass the amplification. The combo XLR/TRS inputs on the front of interfaces are usually for MIC/LINE/INSTRUMENT level input and generally don't bypass the preamps.

My TC Impact Twin has TRS line inputs on the rear and they bypass the amplification, going straight to the ADC. I can also use the front inputs switched to LINE level but these do not bypass the preamps.

 

[AllanDavidson]

Although RCA is the standard for this kind of use, yes, some Home/Pro equipment do TS/XLR Passthrough to converters, but they explicitly tell you. I had a MAudio interface that did this, even though it actually had some buffers and filters before reaching the ADC.

I was was talking in the prosumer audio/interface context, in Pro Audio they basically use XLR for almost everything (due to the tip protection) and label everything, and many companies have things done their way, requiring proprietary cables and connections (specially digital interfaces).

 

[trl]

This is what RCA connectors are intended for, this is why they exist, it means "no amplification involved" while on output (or input as well, when dealing with a capture device).

Unfortunately this is not a "de facto" standard and I'm not even sure it should be. However, The Audient interface we were speaking about is using TRS plugs for the inputs that are bypassing the gain chip inside.

 

[Erosenbe]

RCA is two conductors. Something coaxial like RCA, BNC, or RG-XX is usually best there.

Instruments use TS for two conductor signal, which is okay but maybe not optimal.

TR*S is 3+ conductors but less robust than XLR, and makes contact across conductors when inserting. But TRS is compact and cheap and can be miniaturized to 3.5mm and 2.5mm so it is still a reasonable compromise.

Pin connections like XLR, USB, RJ-XX and various DIN connectors are preferable for 3+ conductor inputs and outputs but they have been bulky until recent times. The XLR housing -- the part that clicks -- can also be additionally connected to a conductor as an additonal conducting path, but usually isn't, per Neutrik.

Nowadays we do have cheap usb-c pd which carry some pretty good power and signal (edit: for serial digital applications like audio/video) but USB is still newish and some issues are still be worked on. There have been a lot of issues with cords being yanked and ripping up pcbs and such on cameras. Whereas barrel connections seem to have a bit more tried and true know how for device longevity.