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Review and Measurements of NAD M51 DAC and Digital Preamp

m8o

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Some amps/pre amps can handle very large inputs. Some cannot. I know preamp makers of old were pretty thorough specifying headroom or overload levels (this is how I know my old Perreaux pre amps can handle ungodly levels of input voltage and not clip).

- If your preamp specs overload [clipping] and is say at least 5V p-p or (better) higher, you should be safe using the 0db ouput of the M51 and not incurring distortion. But at 5V, it is close, and distortion could be setting in. I usually like to see a device not overload until 7V or higher.

- But if input is spec'ed at a hard 1v, 2v p-p, anything over is causing distortion due to input clipping; which has you listening to the glorious sound of square waves (ie pure odd harmonics) for the transient moments when input level is high. (I kid about it being glorious)

This touches on why people swap equipment. Synergy. You note a very noticable 'softness' when the M51 is -10db down. I have tried that and many other volume levels in the past driving my MHA-100 headphone amp. And I could not detect any difference in attack or dynamics. It's a black art. ;)
 
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Cunuu Kum

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Thank you for your answer!

Specification of X-i125 says:
In Level (CD/AUX...) < 300mV
In Level Amplifier < 1,1V

NAD M51 is connected to CD In... <300 mV - this is the lowest voltage that is expected, right?
Sorry for silly questions
 

Cunuu Kum

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BTW! Guys, here is the answer from NAD Electronics's support:

Hello,

Thank you for contacting the NAD Electronics Support Crew!

The question you are asking is primarily based on personal preference. No one can tell you where to put your volume to get the best sound. Only you will know what sounds best to you. I hope this makes sense.

Further to your question, there is compression happening when using a lower volume. When set to 0dB, there are no changes or adjustments made to the music. When set to -10dB, your music is getting "compressed" to bring the volume down. This will not effect the quality of your music but you will notice that is sounds a bit softer.

In summary, 0dB is best for making sure that your audio is true to sound. However, if you prefer how it sounds at -10dB, this is fine and I would encourage you to continue using the M51 this way. It's entirely up to you.

I hope this helps! Please let me know if I can help you with any other questions or concerns.

Kind regards,
Jade L.
BluOS Support Crew Analyst
 

Cunuu Kum

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Today connected Nad M51 directly to amplifier Advance acoustic X-i125 (skipped integrated preamp in my X-i125).
It sounds better!
The “regular” volume on Nad m51 is betwen -32Db and -15Db.

But I’m in doubt.. :))
Sorry I’m wondering if I miss any “quality” at so low volume?
I’m listening regular CDs and Hi-res...

Thanks for your help! :)
 

treuben

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I think there are a few concepts some people are confusing here (if I'm understanding things correctly). The distortion vs level thing is not related to the output volume setting per se but to the digital signal level.. so it doesn't matter if you listen to the DAC at -15 or -1, there should be the same degree of distortion with signals that fall into those poorer performing digital signal levels (or at least, the fidelity of the volume control mechanism was not measured as such). If a recording is made at lower digital levels (say, a non-compressed classical recording with lots of headroom and/or a lot of content that is digitally quiet) then you may be subject to more of this kind of distortion since you'll be turning the output or your amp's volume up thereby making those quieter, more affected sounds louder.

I don't know about the audibility of this though.. many people love the M51 and I have used it driving power amps directly and enjoyed it very much. I have seen praise for its sonics from public forums almost totally exclusively. I myself can't detect any changes in dynamics at different volume levels (I have a stepped attenuator at the input of my power amp so I can experiment with different levels from the DAC) and it's always seemed very natural to me. I'm old and my hearing is not great admittedly but I hear sibilance in a lot of sources and it bothers me, and the NAD does not.

Does anyone feel like they can hear this issue in practice? How many dB down is it really for frequencies that we can hear? (There's a fair chance you can hear more than I can!)

What I think may affect people's practical playback might be all that ultrasonic content in the output. Perhaps a ferrite core or two or similar HF filter on the output could help prevent your amplification from slew-rate distorting because of the ultrasonics? Some amplifiers have their own filtering and some are happy amplifying AM radio anyway and wouldn't care but there must be some that would find it challenging.
 
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Rigel

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Greetings to all in my second speech in the forum.

First of all, thanks amirm for the NAD M51 test.
¿Can you tell me if the AES / EBU entry of the DAC was used in the test?
I mention it because I have one for about two years and I am very happy with it and managed to improve it from the digital section.
The USB input in my opinion is the worst result has given me and I have significantly improved the results, using the AES / EBU input from a USB / AES converter.
A greeting.
 

formdissolve

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These units sell for a fairly decent chunk of change these days.. NAD made a slightly cheaper version (cheaper build quality) of this unit called the C 510. Looking at the teardown of the two units side-by-side they are physically about 99% identical internally. I thought I read that the C 510 had slightly worse specs, but I can't find that. Apparently they sound the same on the latest firmware.

I wonder if they made any other changes to the software which would affect any measurements? I doubt it, but would be interested to see it on the bench because these are cheaper. I'm guessing the M51 was just beefier for the Masters series and this one is scaled down to sell as Pre.

Same specs from the respective manuals:

M51:

Rated distortion (THD+N with AES 17 flter) <0.0005% (ref. 1 kHz 0 dBFS)
<0.002% (ref. 1 kHz -60 dBFS)
IM distortion <0.0001%
Signal-to-noise ratio < -123 dB (ref. 0 dBFS 2V out)
Channel separation > -115 dB (ref. 0 dBFS Volume -1dB)
Sample rate 32 kHz to 192 kHz (USB and digital S/PDIF)
Frequency response ±0.5 dB (ref. 20 Hz – 96 kHz @ 192 KHz sample rate)
Output level 2V (ref. input 0dBFS)

C510:

Rated distortion (THD+N with AES 17 flter) <0.0005% (0dBFS)
<0.002% (-60dBFS)
IMD Distortion 0.0001%
Signal/Noise Ratio <-123dB (ref. 0dBFS 2V out)
Channel Separation >-115dB (ref. 0dBFS Volume -1dB)
Sample Rate 32kHz to 192kHz (USB and digital S/PDIF)
Frequency Response ±0.5dB (ref. 20Hz - 96kHz @ 192kHz sample rate)
Output Level 2V (ref. input 0dBFS)


https://nadelectronics.com/product/c-510-direct-digital-preamp-dac/
 

Rigel

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Hi pvehling.

Indeed they are almost the same, at least in the analogue part, for whose modification I used precisely the C510 service manual.
As for the firmware change, apparently, the manufacturer made only a gain adjustment based on the dB adjustment. There are people who have noticed quality differences depending on the firmware, but I could not make the comparison in my hardware version. I have the last.
 

markie900

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These units sell for a fairly decent chunk of change these days.. NAD made a slightly cheaper version (cheaper build quality) of this unit called the C 510. Looking at the teardown of the two units side-by-side they are physically about 99% identical internally. I thought I read that the C 510 had slightly worse specs, but I can't find that. Apparently they sound the same on the latest firmware.

I wonder if they made any other changes to the software which would affect any measurements? I doubt it, but would be interested to see it on the bench because these are cheaper. I'm guessing the M51 was just beefier for the Masters series and this one is scaled down to sell as Pre.

Same specs from the respective manuals:

M51:

Rated distortion (THD+N with AES 17 flter) <0.0005% (ref. 1 kHz 0 dBFS)
<0.002% (ref. 1 kHz -60 dBFS)
IM distortion <0.0001%
Signal-to-noise ratio < -123 dB (ref. 0 dBFS 2V out)
Channel separation > -115 dB (ref. 0 dBFS Volume -1dB)
Sample rate 32 kHz to 192 kHz (USB and digital S/PDIF)
Frequency response ±0.5 dB (ref. 20 Hz – 96 kHz @ 192 KHz sample rate)
Output level 2V (ref. input 0dBFS)

C510:

Rated distortion (THD+N with AES 17 flter) <0.0005% (0dBFS)
<0.002% (-60dBFS)
IMD Distortion 0.0001%
Signal/Noise Ratio <-123dB (ref. 0dBFS 2V out)
Channel Separation >-115dB (ref. 0dBFS Volume -1dB)
Sample Rate 32kHz to 192kHz (USB and digital S/PDIF)
Frequency Response ±0.5dB (ref. 20Hz - 96kHz @ 192kHz sample rate)
Output Level 2V (ref. input 0dBFS)


https://nadelectronics.com/product/c-510-direct-digital-preamp-dac/
Hi, sorry I have to ask you. How do you update the firmware on the NAD C510 and where do I find the latest firmware?
 

Mat

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Got one of these and have a couple comments

1. My source has HDMI out and optical out, so I used both into the M51 to A/B test. I was hoping HDMI would have less jitter or something, but at the moment I can say that optical is superior to the HDMI implementation here (sadly). Vocals sound compressed on HDMI, and when I flip over its like changing a significant filter, theres more space and detail. HDMI aint bad, but it's nerfed.

2. Tried checking the firmware and while it shows up as the latest, the mode that displays those options only shows up for like 2 seconds before the whole screen goes blue. Likewise, when trying to update the firmware it just hangs on the "Bootloader 1.21" message (someone on headfi had this issue too a decade ago but didnt reply with a solution in the thread)

3. I think it sounds great and I hear noticeable improvements from my Topping E50 for music, but comparing the two on a technical level the NAD M51 is much, much noisier. I dont have tools to test properly, but on my integrated amp (via RCA outs) headphone out, volume cranked, and just alternating sources with max volume, there's a constant stream of white noise coming out of the M51 while the E50 is silent by comparison. The M51 also has a little 'blip' I hear in the noise every 2 seconds or so like a metronome. Thankfully these are at volume levels no human should use, but its still disappointing that the cheaper DAC is taking a clear win here. (granted, the Topping is 10 years younger, technology improving and whatnot)

Not sure if there's a way to isolate or delve into that noise issue, or its just the way it is. (not sure if an XLR to RCA adapter would work, and avoid the RCA out?)
 
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Marc v E

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Got one of these and have a couple comments

1. My source has HDMI out and optical out, so I used both into the M51 to A/B test. I was hoping HDMI would have less jitter or something, but at the moment I can say that optical is superior to the HDMI implementation here (sadly). Vocals sound compressed on HDMI, and when I flip over its like changing a significant filter, theres more space and detail. HDMI aint bad, but it's nerfed.

2. Tried checking the firmware and while it shows up as the latest, the mode that displays those options only shows up for like 2 seconds before the whole screen goes blue. Likewise, when trying to update the firmware it just hangs on the "Bootloader 1.21" message (someone on headfi had this issue too a decade ago but didnt reply with a solution in the thread)

3. I think it sounds great and I hear noticeable improvements from my Topping E50 for music, but comparing the two on a technical level the NAD M51 is much, much noisier. I dont have tools to test properly, but on my integrated amp (via RCA outs) headphone out, volume cranked, and just alternating sources with max volume, there's a constant stream of white noise coming out of the M51 while the E50 is silent by comparison. The M51 also has a little 'blip' I hear in the noise every 2 seconds or so like a metronome. Thankfully these are at volume levels no human should use, but its still disappointing that the cheaper DAC is taking a clear win here. (granted, the Topping is 10 years younger, technology improving and whatnot)

Not sure if there's a way to isolate or delve into that noise issue, or its just the way it is. (not sure if an XLR to RCA adapter would work, and avoid the RCA out?)
Interesting. Ime the hdmi is as good as optical, no noticable difference between the two. (The measurements here seem to confirm they are identical.)

I do have a topping dac/pre too, the dx7pro. After a few days of comparing I came to the conclusion the Topping sounds clearer, more true to the source. This is espescially noticable in the bass, however nice the sound signature of the m51 or in my case the c510 is. Ymmv. I think at this level this shows there is lots at play with preference and other things than sound alone. I would recommend trying the path of measuring and adjusting your speakeroutput by eq. Umik microphone and camilla in moode are a vast change compared to any dac at any price.
 
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Mat

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Interesting. Ime the hdmi is as good as optical, no noticable difference between the two. (The measurements here seem to confirm they are identical.)

having spent more time with it....its for sure different, and I find myself opting for the optical every session for the clarity. That said, been thinking about it and its possibly the fault of the source (apple tv), with it merging the audio into its A/V output then needing to be extracted again, with the optical bypassing some processing? Only explanation I can think of
 

Marc v E

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having spent more time with it....its for sure different, and I find myself opting for the optical every session for the clarity. That said, been thinking about it and its possibly the fault of the source (apple tv), with it merging the audio into its A/V output then needing to be extracted again, with the optical bypassing some processing? Only explanation I can think of
The first thing that springs to my mind when I hear this that is has to do with sample rate. I never tested this double blind, but I would swear I notice when the output is 48 khz while the original recording was in 44.1 khz.

I think the hdmi is outputting in 48 khz as that is the standard rate accompanying video and apple tv is a tv device primarily. Btw I would venture a guess to say the apple tv outputs 48 khz in the optical spdif too. In short: I'm not sure of the audibility of all this but my inkling is that this can affect the endresult.

Maybe you could check the settings on the apple tv if there is something else going on too. Is it set to stereo or upmixing etc?
 
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Mat

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The first thing that springs to my mind when I hear this that is has to do with sample rate. I never tested this double blind, but I would swear I notice when the output is 48 khz while the original recording was in 44.1 khz.

My guess would be the hdmi is outputting in 48 khz as that is the standard rate accompanying video and apple tv is a tv device primarily. Btw I would venture a guess to say the apple tv outputs 48 khz in the optical spdif too. In short: I'm not sure of the audibility of all this but my inkling is that this can affect the endresult.

ATV converts everything to 48k regardless so sample rate wouldnt be the difference. This convo is making me want to get an old airport express though for the 44.1k bit perfect output...for science
 
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