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MOTU M4 interest?

philosobyte

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I have the M4. I use its mic preamps to record grand piano with two small-diaphragm omnidirectional microphones. I have also used it with small-diaphragm and large-diaphragm cardioids for vocals. The preamps are significantly hotter than my old UR22, but I don't own any dynamic microphones to comment on how well it does there without a Cloudlifter.

I remember using a Khadas toneboard in conjunction with my UR22 and M4 to do some hacky measurements. I no longer have that data and due to coronavirus I no longer have access to my Khadas and UR22, but my conclusion at the time was that the M4's DAC and ADC are far superior to the UR22.

I had also concluded at the time that the M4's mic preamps had a small to zero noise advantage over the UR22 for a given output level. However, I realize retrospectively that I was comparing with the mic plugged in and phantom power on, so microphone self-noise was being taken into account.

In terms of headphone output, I was sending the M4's RCA output to an Atom because the JDS Labs Atom sounded better to me with my DCA Aeon 2 Closed and my LCD2C Closed. There's most definitely bias at play, but hey, if bias can make something sound better with the gear I already have, then why not use it :D
I am currently using my M4's line outs with a pair of JBL 705Ps (for those wondering, no, I have no trouble with F#5).
 

lc155

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I have the M4. I use its mic preamps to record grand piano with two small-diaphragm omnidirectional microphones. I have also used it with small-diaphragm and large-diaphragm cardioids for vocals. The preamps are significantly hotter than my old UR22, but I don't own any dynamic microphones to comment on how well it does there without a Cloudlifter.

I remember using a Khadas toneboard in conjunction with my UR22 and M4 to do some hacky measurements. I no longer have that data and due to coronavirus I no longer have access to my Khadas and UR22, but my conclusion at the time was that the M4's DAC and ADC are far superior to the UR22.

I had also concluded at the time that the M4's mic preamps had a small to zero noise advantage over the UR22 for a given output level. However, I realize retrospectively that I was comparing with the mic plugged in and phantom power on, so microphone self-noise was being taken into account.

In terms of headphone output, I was sending the M4's RCA output to an Atom because the JDS Labs Atom sounded better to me with my DCA Aeon 2 Closed and my LCD2C Closed. There's most definitely bias at play, but hey, if bias can make something sound better with the gear I already have, then why not use it :D
I am currently using my M4's line outs with a pair of JBL 705Ps (for those wondering, no, I have no trouble with F#5).

That's fair enough, I was just mostly wondering if the headphone output is 'technically' sufficient on paper for most headphones bar the most demanding kind, as that would allow me to ditch my old o2dac and I always appreciate a cleaner setup.
 
D

Deleted member 12642

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I had really bad luck with my M4 and my HP z800 but I since remedied that with a new computer. Since then it's been flawless and I'm really happy with the interface. Turns out my z800 had unsolvable issue with it's USB controller and I didn't have much choice but to just get rid of it. Tried an RME babyface and had the same issues so it was definitely the computer. If they make an 8 channel version I will probably buy it.
 

jae

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Surprising, given the incredibly low output impedance of the headphone output on the M2 (Less than 0.05ohms). We also know the distortion and noise from measurements places the M2 in a very good spot as well. I know the 650s can peak at 530ohms in the bass regions, but my technical knowledge isn't great enough on this subject to say if the M2 would struggle to deliver enough power in that region, but if it is getting loud enough, it should. The distortion figures to me seem unlikely that it would be clipping (which is what you'd probably be hearing if bass and midbass sounded anemic).

From another thread here the headphone out of the M4 was measured at "SE 1/4" TRS - 2.681Vrms". Not sure if it is much different on the M2.

From other sources the HD650 needs about 1.7-1.8 Vrms @ 107 dB SPL, 3.2-3.6 Vrms @ 114 dB

So it seems like it should be fine for regular listening.
 
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Great workhorse.

For sure, got 10 years out of it and it's still pretty fast today. I am very much appreciating my cooler room and reduced electric bill, as well as feeling like I time traveled into the future in terms of DAW performance.
 

lc155

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From another thread here the headphone out of the M4 was measured at "SE 1/4" TRS - 2.681Vrms". Not sure if it is much different on the M2.

From other sources the HD650 needs about 1.7-1.8 Vrms @ 107 dB SPL, 3.2-3.6 Vrms @ 114 dB

So it seems like it should be fine for regular listening.

This includes the >500ohm bass peaks, I take it? Just trying to see if the users commenting that it sounds anaemic are just mistaken.

@solderdude, you seem to know your stuff from things I've seen before from you, especially in this realm. What's your take, if I may ask?
 

solderdude

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2.7V and 105dB/V = 113dB SPL peak so about 90 to 95 Phon average with music = loud enough for casual and 'active' listening but just not enough for listenening at impressive levels. Of course person A may be easier to impress than person B. ;)

An amplifier provides a voltage, the drawn power isn't any problem (at impedances above say 40 Ohm).
At the impedance peak a headphone draws less power but also requires less power.
Only the output voltage of an amplifier is of significance.
 

jae

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I had posted this earlier but I don't know why it didn't go through:

"Yes in the first case at 107 dB the p-p was about 5V and about 9V at 114 dB. Those tests were done using an O2 amp I believe. The motu (M2) at least can do 23 mW into 300 ohm so I assume the M4 is the same or better. So it seems like it could struggle at those extreme levels with very dynamic music but it should be good to about 112.4 dB SPL on the HD650 assuming those specs."
 

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lc155

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Yeah, sounds fair enough. I never listen that loud as it is due to paranoia with tinnitus, so I won't be needing to blow my eardrums anytime soon; as long as it provides enough juice on paper to sound the same as other amps like the Atom at realistic/safe listening levels, then I'm happy.
 

f1shb0n3

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I've had it for a couple of weeks and am very happy with it as an all-in-one solution. The headphone amp can power a pair of Sennheiser HD6XX at about 75% volume for typical rock music and sounds clean in the process. I like having the option to use the 3/4 outputs to run an external headphone amp. Anecdotally, I think my speakers sound a bit better from the unbalanced 1/2 monitor outputs than they did from my Atom/Modi 3 combo. I suspect this is probably because the volume control appears to be passive, whereas on the Atom the preamp outputs are connected to the headphone amp and could potentially have been clipping my DSP input. Just a theory.

Build quality is exceptional for the price. The knobs are excellent.

I haven't used any of the ADC functionality yet but I will soon.

The only feature I'm missing is is that I wish the headphone output could be assigned a different mix from the monitor output.

How do you send your computer audio to output 3-4 of the Motu M4?
I'm considering upgrading from M2 to M4 for the 3-4 line outputs to use with a headphone amp while using 1-2 for studio monitors, but some claimed that I need additional virtual audio device software to be able to do it. I'm using MacOS btw.
 

philosobyte

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How do you send your computer audio to output 3-4 of the Motu M4?
I'm considering upgrading from M2 to M4 for the 3-4 line outputs to use with a headphone amp while using 1-2 for studio monitors, but some claimed that I need additional virtual audio device software to be able to do it. I'm using MacOS btw.
The Windows driver splits the Motu M4 into one output for channels 1-2 and one output for 3-4. Unfortunately, this is not the case for Mac OS, even after installing the driver Motu provides.
 
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Deleted member 12642

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Surprised to hear another user not liking the hd6xx with the motu m stuff, I've got 6xx and the thing drives it easily to painful levels, no idea what max volume is like. Only ever have to turn it to like 11oclock and that's too much for me most of the time.
 

lc155

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Surprised to hear another user not liking the hd6xx with the motu m stuff, I've got 6xx and the thing drives it easily to painful levels, no idea what max volume is like. Only ever have to turn it to like 11oclock and that's too much for me most of the time.

Where did you see that? I don't see it on this thread recently.
 

lc155

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Oh, you'd already replied in this thread, so I didn't think you meant that. Solderdude already confirmed though that the M2/M4 is more than sufficient.
 

Minigun

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How do you send your computer audio to output 3-4 of the Motu M4?
I'm considering upgrading from M2 to M4 for the 3-4 line outputs to use with a headphone amp while using 1-2 for studio monitors, but some claimed that I need additional virtual audio device software to be able to do it. I'm using MacOS btw.

As a class compliant device it is seen as a 4-channel device, in Linux and apparently also in MacOS. In Windows it's two 2 channel devices, so choosing one is trivial. In Linux I use a virtual stereo device that duplicates the stereo signal to quad, channels 1/2+3/4.

Could you perhaps use the unbalanced output 1/2 for your headphone amp and the balanced output 1/2 for the monitors (or the other way)? The M4 volume control knob sets the volume digitally, so there's no fear of losing any sound quality anyway.
 

f1shb0n3

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As a class compliant device it is seen as a 4-channel device, in Linux and apparently also in MacOS. In Windows it's two 2 channel devices, so choosing one is trivial. In Linux I use a virtual stereo device that duplicates the stereo signal to quad, channels 1/2+3/4.

Could you perhaps use the unbalanced output 1/2 for your headphone amp and the balanced output 1/2 for the monitors (or the other way)? The M4 volume control knob sets the volume digitally, so there's no fear of losing any sound quality anyway.

Thanks for explaining the MacOS behavior of M4 outputs!

I’m using M2’s balanced output for monitors and unbalanced for headphones and it works great. Only issue is after I use headphones and forget to turn the volume down or turn on my monitors accidentally (using a remote power switch) and my monitors blast at full volume. I guess I’ll figure out some virtual device solution and get M4 or get a Topping A90 to use as headphone amp/monitors preamp and switch.
 

lc155

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Thanks for explaining the MacOS behavior of M4 outputs!

I’m using M2’s balanced output for monitors and unbalanced for headphones and it works great. Only issue is after I use headphones and forget to turn the volume down or turn on my monitors accidentally (using a remote power switch) and my monitors blast at full volume. I guess I’ll figure out some virtual device solution and get M4 or get a Topping A90 to use as headphone amp/monitors preamp and switch.

If I'm reading correctly, the 3/4 line outs on the M4 are not volume controlled and always output at maximum power, which makes them perfect for running into an amp. Then you can use the amp solely for headphone control and the M4 volume knob for your monitors, since it won't affect the 3/4 outputs.
 

f1shb0n3

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If I'm reading correctly, the 3/4 line outs on the M4 are not volume controlled and always output at maximum power, which makes them perfect for running into an amp. Then you can use the amp solely for headphone control and the M4 volume knob for your monitors, since it won't affect the 3/4 outputs.

True - only issue is that as @Minigun explained in Windows M4 shows as two separate audio devices - one for 1-2 output (volume controlled) and another for 3-4 output (line out at max power), while on MacOS Motu M4 shows up as a single 4-output device where only channels 1-2 play system audio. With some additional virtual device software it should be possible to route system audio to both 1-2 and 3-4 outputs. Probably in Audio MIDI Settings / Configure speakers it would be possible to set Left and Right to be channel 3 and 4 but this won't be very convenient.

I'm choosing to stick with M2 for the moment, it works very well for balanced monitors and unbalanced headphone amp. As long as you remember to turn down the volume down when using studio monitors.
 
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