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Motu M4 Audio Interface Review

TNT

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Given the limited dynamic range and high distortion of vinyl, why use hi-res?

Well, if one love vinyl, one would of course would like to secure the absolute most thruthful reproduction of all the hiss, noise, varp and rumble - no?

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TNT

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True, but what do amir say "very nice"?

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Blumlein 88

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I switched from the Scarlett to one of these last year. Honestly I just wanted the shiny VUs as it's so much easier to dial in levels - I have a Fractal AX8 going into the XLRs up front 90% of the time with my PC running through USB. Now I'm even more thrilled that I made the switch. I don't think the Adam T7V I use to monitor (and also love) are anywhere close to how clean this interface is.
You know the Scarlett gear, at least the better ones, seem to be craftily made on the edge of inaudibility. Meaning some of them are good enough you'll likely hear no difference vs better gear or it will be a tiny very slight one heard only rarely. To me that is pretty good for low cost entry level gear. They did make a couple particular versions not quite that good. But mostly Scarletts are that good.

The M2 and M4 appear to be even better and nothing wrong with a little gilding the lily. MOTU doesn't yet have anything comparably priced to the Scarlett 18i20 with 8 microphone preamps. But maybe in the near future they'll have an M8 or something like that.
 
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amirm

amirm

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The filter is judged as "very nice" but I would like to remind the audience that according to the sample theorem in order to recreate a perfect wave, all inofrmation above FS/2 must be filtered away. Here, 22,05khz is only 12 db down... So technically, this is far from excellent.
The "filter" was not judged as excellent. I said this: "The default filter is not as sharp as it should be (typical) but has excellent attenuation: "

The word excellent applies only to the attenuation of the stopband, not its cut off frequency. I also mentioned that it was not sharp enough so don't know what the objection is about.
 

daftcombo

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Performance is more or less the same as Focusrite Scarlett 2i2 or 4i4.
 

3125b

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The headphone output is way worse also, to tue point of being almost unuseable with both high and low impedance headphones (incl. horrrible crosstalk, wich Amir didn't measure unfortunately).
 
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bennetng

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Frequency response at full 192 kHz showed some odd peaking:
index.php

May have something to do with this:
https://prosound.ixbt.com/interfaces/motu-m4.shtml
image6s.jpg


ak5554.png
 

BDWoody

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The M2 and M4 appear to be even better and nothing wrong with a little gilding the lily. MOTU doesn't yet have anything comparably priced to the Scarlett 18i20 with 8 microphone preamps. But maybe in the near future they'll have an M8 or something like that.

Have you done much with the Motu 896?
 

Atanasi

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According to the datasheet:
With a standard USB-C power adapter, the M2 can be used as a stand-alone preamp and basic mixer, with no host computer required.
Maybe this use case could also be measured, connecting a signal source and measuring the monitor output. I would be interested in using this for mixing and converting an unbalanced signal to balanced.
 
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AudioSceptic

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No reason, other than it is going into a miniDSP SHD and that is the SHD resolution. What would you suggest?
Blumlein88 has given a reason to use a high sampling rate which I haven't heard/read before, but I'd have thought that 16x48 would be ample. The DR of vinyl is equivalent to 12 bits at most, but 16 is the CD standard so you might as well use that. Using 24x96 instead of 16x48 will make your files 3x the size. Is that really worth it?
 

Koeitje

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These kind of reviews make me happy. Just a good solid allround product.
 

AudioSceptic

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I've run into situations doing needle drops where there seems to be some interaction with peaky moving coils and the lower sample rates (less than good filters just past ultrasonic I suppose). Going to 88 khz or 96 khz takes care of it and the needle drop sounds same as the LP itself.
Is the difference really audible? What about using 48k, which will halve file sizes (for the same bit-depth)?
 

AudioSceptic

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The filter is judged as "very nice" but I would like to remind the audience that according to the sample theorem in order to recreate a perfect wave, all inofrmation above FS/2 must be filtered away. Here, 22,05khz is only 12 db down... So technically, this is far from excellent. "Very nice" would be say 130 dB down.

View attachment 81178

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Quite. What is it with these lazy filters? See my reply to Amir.
 
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AudioSceptic

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The "filter" was not judged as excellent. I said this: "The default filter is not as sharp as it should be (typical) but has excellent attenuation: "

The word excellent applies only to the attenuation of the stopband, not its cut off frequency. I also mentioned that it was not sharp enough so don't know what the objection is about.
These lazy filters (flat to 21k not 20k, and reaching full attenuation at 24k instead of 22k) look like they're meant for 48k sampling and they couldn't be bothered to provide a proper one for 44k. Thoughts?
 

Atanasi

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These lazy filters (flat to 21k not 20k, and reaching full attenuation at 24k instead of 22k) look like they're meant for 48k sampling and they couldn't be bothered to provide a proper one for 44k. Thoughts?
That's what I thought, too. However, for a DAC a little ultrasonic noise is not too harmful. For ADC, it might induce sampling artifacts. ADC was tested with 48 kHz, maybe we could verify if 44.1 performs the same.
 
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