NAD M51 Direct Digital D/A converter John Atkinson May 2014

John Atkinson reviewed the M51 in May 2014 (Vol.37 No.5):

I've been using NAD's Masters Series M51 Direct Digital D/A processor ($1999) as one of my references since summer 2013. Jon Iverson had enthused about the M51 in his July 2012 review, concluding that he preferred DACs "that reveal as much as possible about what was captured on the tape or in the digits, and couldn't care less about adding a rose-colored tint to dodgy digital sound. In this regard, the NAD M51 succeeds with a wonderfully detailed and revealing sound best described as honest, with a friendly smile." My own experience of the M51 (my sample was serial no. H33M5103771; his was H1XM5101162), driven by the NAD M50 Digital Music Player and Digital Music Vault M52, echoes Jon's. It is transparent to recorded detail without the sound becoming, in that classic phrase, "ruthlessly revealing."

Compared to the half-again-as-expensive Electrocompaniet Classic ECD 2 ($3100), which I reviewed in December 2013, the M51's sound was lighter balanced, with less authoritative low frequencies but with a deeper soundstage, longer reverb tails, and a filigree retrieval of fine detail. Playing my 2000 recording of Robert Silverman performing Beethoven's Piano Sonata 18 (24/88.2 master AIFF file from CD, OrpheumMasters KSP-830), the NAD was slightly better at decoding the ambient cues and the leading edges of the piano's percussive character. In direct comparison, the Electrocompaniet's overall presentation of the Bösendorfer was more true to the sound of the piano than the recorded acoustic, I felt.

When, in February 2014, I reviewed the Auralic Vega ($3499)—which is almost identical to the NAD in its feature set, including a digital-domain volume control—the Vega gave more weight to Jaco Pastorius's subterranean bass-guitar notes on a 24/96 needle drop of "Overture—Cotton Avenue" from Joni Mitchell's Don Juan's Reckless Daughter (LP, Reprise K63003), while the M51 focused more on the sound of Mitchell's open-strung acoustic guitar. Ultimately, the overall sound was a little more airy through the M51, with a cleaner if leaner balance. I ended up preferring the Auralic processor, but the NAD gets close to it at 57% of its price.

A poster to our website reported that the M51's earlier v1.39 firmware is the best sounding. Turning on the M51 with its Input button pressed revealed that my sample was running the v1.41 firmware, which is supposed to have less bass and to sound not quite as dynamic as v1.39. I downloaded the v1.39 firmware here and rolled the M51 back to that version by loading the code onto a USB stick, plugging it into the Upgrade USB port on the M51's rear panel, and following the instructions in the appropriate NAD software bulletin. All appeared to go correctly, and turning on the M51 with the Input button pressed now indicated that the v1.39 firmware had been installed.

This is hardly something for which you can perform an A/B test, but listening to the Thelonious Monk–influenced "Rainbow's Cadillac," from a downloaded Bruce Hornsby concert from Oregon Zoo, in Portland (16/44.1 FLACs), I discovered that the reader had been correct. The bass guitar and kick drum did indeed sound a little fatter than with the latest firmware. This was a benefit with the Joseph Perspective and Wilson Alexia speakers I used in my listening, but not with the Vivid Giya G3s. Who'd a thunk it? (footnote 1)—John Atkinson

Footnote 1: In his "Manufacturer's Comment," NAD's Greg Stidsen wrote that "Software v1.41 dropped the gain by 1dB, to give that little bit of extra headroom. While 1dB may be at the threshold of human perception, a keen ear will hear the slightly louder playback of v1.39 as "better." Other changes in v1.41 include a revision of the Polarity setting logic, and the addition of an auto standby to comply with EC energy policy. No changes were made that would affect frequency response or dynamics." I reloaded the v.1.41 firmware into my sample of the M51 and rechecked the maximum output level at 1kHz. It was indeed exactly 1dB lower than it had been with this sample loaded with the v.1.39 firmware and with Jon Iverson's original review sample.—John Atkinson
NAD Electronics International
633 Granite Court
Pickering, Ontario L1W 3K1
(800) 263-4641

mrhyfy's picture

Great write up seems like a fantastic dac. 

I love the Marantz AV7005 and believe it offers outstanding performance HOWEVER I think you might be doing the Nad a deservice by feeding a $2k dac into a $1700 home theater preamp.

The particular problem for me is that the signal from the Nad has to run through the ADC first,then the dsp then the DAC in the Av7005.Ultimately you're reviewing the dac in the Marantz AV7005!!

 I realize that you used the pure direct mode but it is not analogue pass through in this receiver. 

Would it be possible to evaluate the Nad dac with the signal DIRECTLY connnected  to your amp?  That's the whole point of having the volume control feature in the dac.

Jon Iverson's picture

Whenever I receive a DAC that can also run as a preamp (with volume, input switching, etc), I always connect the DAC directly to my power amps. I then compare this sound to  running via the Marantz in Pure Direct Mode. Rarely have I (or those who are listening with me) ever been able to detect a difference.  To compare to other DACs (which do not have a preamp function) I usually run everything via the Marantz - maybe not perfect, but as fair as I can make it.

VandyMan's picture



I love that they included HDMI, but who only needs two HDMI inputs? I need five and I don't have that complex a system. Before someone suggests adding an external switch, keep in mind that they sometimes causes problems. I have two devices that refuse to work when run thru a switch (and I tried several brands). Besides, one of the points of a "home theater" pre-amp, two channels or not, is to act as a master control switch to all sources.

Surge's picture


Thank you for the review Jon.  I would be really interested in knowing how it compares to the AMR DP-777 that was reviewed in March.

I know the AMR is $5,000 vs. $2,000 for the NAD; but I am curious to know if in your opinion it is worth the additional cost.

Many thanks

Jon Iverson's picture

Surge - I have not yet heard the AMR in my system.

raykkho's picture

Thank you Jon for the very exciting review.  One thing though is how can someone merge his M51 with an existing MC home theatre setup, when the M51 does not have any analogue input or HT bypass? I hate to add an AB switch before the poweramp but can't see how it could be done any other way. sad

Amir the Great's picture

last Xmass I did a mistake. Paying 15000SDK for the M51.
it sounds vry good as JA's review, if it souns! The USB Windows driver is a hell. Win8.1 find the dac some times!!!
wrot to NAD. answer: M51 was before Win 8.1!!! and?

How... mush time putin on a product? ok, gott back to win7, same hell. the PC find the dac sametimes!

then they came with "NAD USB Audio Driver for Windows 7 and above" wow the king waked up finally!

but problem was the same. M51 sings when Trump write the order!

Even the JA link above is empty. even if the song finish, efter some minuts the dac dyes! turn itself off! and again Windowes can not find it!

I should turn off the dac Not mr. Stidsen! "is there any body at home?"
shall I teche him a warm bird sings better than a frozen one?

NAD does NOT send the first v1.39 firmware to anybody!!! why? Ayatollah's fatwa maybe.

my 15000 NAD does NOT work properly!

a good product is good in evry manner. NAD isn't an eBay $15 dac who NOT works when you want!

ergonomically NAD is NOT wright either. what happen if U can't find the remote? or battery ...
2 small bottoms at front panel (volume up/down) costs $1. it is the Master NAD isn't? after so many years of iconic amps? oh sorry it is a dac not an amp!

the hole gole is playing music when you want. not waiting for the president to push the bottom.

too tired to play on the NAD.


lev80's picture

Yes! its a great product and there is nothing wrong with the M51. No one forced you to buy it if its ergonomically dose not work for you.
I got my M51 early 2014 brand new and never had any issues with it nor its windows drivers, worked like a charm all these years and still i enjoy it everyday. and i don't think i could depart with it although my other PARASOUND gear sound much sweeter but there is something special about the soundstage of the M51.
You should have returned it if u felt that its not for you, as simple as that.