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NAD C 390DD Powered DAC amplifier review (Part 1)

  • Like the M2 before it, NAD’s mandate with the C 390DD (AU$3000) is obvious from the get go: digital with a capital D. The rear panel says it all: NAD have dispensed with analogue input options – unless you purchase an optional slot-in module – so that the stock C 390DD’s inputs are ALL digital: 2 x coaxial, 2 x optical, 1 x AES-EBU and USB (Type B – for your computer). There are also front- and rear-facing USB slots (Type A – for external hard drives and USB keys). Digital source connectivity options are comprehensive. All USB inputs are buzzword compliant (“asynchronous”) and top out at 24/96. S/PDIF digital inputs can handle up to 24/192.

    There is no separation of church and state with the C 390DD. However, do not think of this as a DAC and amplifier housed in the same chassis. It’s more than that: DAC and amplifier are fused together (as one). Think of it as a DAC that amplifies.

    Once ones and zeroes are fed into the unit, some serious processing takes place. Purists might wince at NAD’s compulsory conversion and resampling of the incoming data stream. PCM (Pulse Code Modulation) is re-sampled to 844 KHz and converted via DSP to PWM (Pulse Width Modulation). This PWM controls the output FETs. The FETs feed your speakers. There are no analogue gain stages anywhere inside this unit. None.

    ‘Direct Digital’ is what the spin doctors at NAD call it. This technology has trickled down the product line from the much-fancier looking and much more expensive M2 (AU$7000). Understandably, the C 390DD doesn’t have the trophy cabinet high-end looks of its bigger brother; the C 390DD chassis puts functionality ahead of aesthetics, presumably to keep manufacturing costs down.

    From the M2 product page:

    “M2 is the first implementation of a new amplifier technology called Direct Digital Feedback. Co-developed with UK based Diodes Zetex Semiconductor, and using a unique implementation of their patented DDFA architecture, the M2 redefines what is possible with digital amplifier technology.”

    From the C 390DD product page:

    “Boasting a healthy rating of 150 watts per channel with nearly immeasurable distortion and noise, the C 390DD can effortlessly power demanding high-end loudspeakers. The C 390DD has no analogue stages in the signal path, keeping the music in the digital domain right up to the speaker outputs. This is a true digital amplifier, or more accurately, a DAC that amplifies. All preamp functions are executed in the digital domain without the phase shift, noise and distortion that plagues all analogue designs regardless of price or pedigree.”

    The aforementioned DSP unit also handles the C 390DD’s bass/treble adjustments and room equalisation test tones, which the user can use to attenuate individual frequencies by ear. However, at time of writing, the latter had yet to be fully implemented – it will require a future firmware update. NAD have been insisting that M51 DAC firmware updates are done by approved dealers; it will be interesting to see if this also applies to the C 390DD.

    Other nice things about the C 390DD: the display informs you of the sample rate of the incoming signal and the user can specify (via the menu system) the loudspeaker impedance.

    I have to admit it: my initial expectations were low. When the NAD box arrived I thought I’d already managed to juice the (cough) ‘best’ from the recently arrived WLM La Scala floor standers with either the Red Wine Audio Signature 15 and Audion EL34 Sterling (and PS Audio PerfectWave MKII DAC). Granted, these both work their magic from the lower power output end of town but they both know how to seduce a listener; and the WLMs are of higher sensitivity. The NAD doesn’t walk this way. Its ‘best’ is less lap-dance and more straight talking; and oh my, so many BIG words! There is no sign of pronounced midrange eloquence (Audion) or the tonal finessing of Vinnie Rossi’s integrated. Cat gets early mark from bag: the NAD is more uniformly conservative with voices.

    Initial source material was Redbook FLAC rips played from a Squeezebox Touch via Empirical Audio’s Synchro-Mesh re-clocker.

    Matthew Sweet’s ability to juxtapose the tenderness and roar of heartbreak makes his Altered Beast album a right proper rollercoaster ride. The jumpiness of (ex-Television) Richard Lloyd’s hard-panned guitar was arresting. Moreover, the tonal qualities of the guitar squall and the precision of its placement made me sit up and pay strict attention. The expected arms-length emotional engagement didn’t materialise (the C 390DD is impossible to ignore). Instead, sweetness and DETAIL. The combination of huge swathes of musical information tinged with tip-of-the-tongue sucrose was so compelling I sat listening for too long, lost track of time…and was late for work. Whoops.

    Later that night, Low’s Things We Lost In The Fire and Radiohead’s Kid A. Again: more detail than I’d hitherto witnessed from any DAC-amp combination at this price point. More textural information too – a guitar string sounds closer to the real thing – and better spatial cues that improve soundstage depth and player location. The storm of horns that close Radiohead’s “National Anthem” were superbly separated and moist horn blat could be clearly discerned. No dryness here. Low’s hushed and fragile recordings surrendered more air and acoustic decay giving rise to a better sense of the room/space in which they were recorded. With Alan Sparhawk’s voice closely mic’d and then panned firmly to the right channel, one could clearly and cleanly hear every (heart-)beat of the distant drum that sat some 6ft behind the centre of the speaker plane. Three-dimensions were writ large without the need for constant dynamic theatrics, which themselves are also present and correct when called upon. The NAD won’t emphasise a quality that just isn’t there. Neutrality to the point of ambivalence.

    Until hearing Don’t Try This At Home by way of the NAD C 390DD, I’d rarely given much thought to the musicianship that went into making Billy Bragg’s ‘crossover’ record. With Cara Tivey’s piano given more breathing room, such myopia was swiftly corrected. The NAD again dug deep for detail and exposed the tonal delicacies of piano notes and guitar strings that sit behind Billy Bragg’s (sometimes) boorish vocal turns. Everything felt more ALIVE without resorting to the MSG hyper-taste-tingle of showier – and ultimately lesser – DACs. If I describe the NAD as accurate I’m not doing so pejoratively. If the recording is poor, you’ll know it but this ampli-DAC doesn’t connote disinfectant in a bid for cleaner resolution.

    Bad news, broken gently. I’ve often called out rigidity and greyish tonal colours as hallmarks of a jitter-y sound whereas liquidity and suppleness are signs of a sound less troubled by such timing errors. The C 390DD runs nicely with the latter two qualities. Even with poor recordings one can listen with ease and for extended periods BECAUSE liquidity is so darn obvious.

    Even so, those migrating from warmer, tubular climes might find this take on music initially too stark. Ultimately, those same folk might find it captivating. Like music, can be seen as a collection of separate, brutal events or given a romantic sheen by only considering the period in question as a whole. Think of the NAD as an archeological team exposing a burial site from thousands of years ago; a delicate unveiling of something that has the potential to be unpleasant…if your collection consists of predominantly poor recordings or masters. Wherever you sit on the need for colouration, NAD aren’t giving you any. What they are giving you is a comfy chair and a widescreen representation of an historical (detail) excavation.

    Switching transports from Squeezebox/Synchro-Mesh (S/PDIF) to MacMini (USB) reveals the C 390DD’s universal serial bus input to be less resolving and less alert than its S/PDIF neighbour. When directly compared to a 16/44 S/PDIF feed of the same 2012 remaster, even the 24/96 version of David Bowie’s Ziggy Stardust takes a hit on urgency and joie de vivre. Not even the ever-dependable Audirvana could save it. Diminished transient incision and a lack of overall visual acuity were most obvious. Bass lines showed more pant-seat sag. This USB input might make the NAD more agreeable to brighter loudspeakers but that’s an ass-backwards compromise.

    Repeated listening confirmed it time and again: the C 390DD’s USB isn’t as solid or as vibrant as its S/PDIF. I reached for a KingRex UD384 – a DAC and USB-S/PDIF convertor. Digital audio newbies might think that the latter function is simply format conversion but there’s more going on inside the black box: clocking. Good clocking reduces jitter. Reduced jitter makes for a more enjoyable sound. Chris Sommovigo’s Silverstar digital coaxial and a QED USB cable completed the connection.

    With the KingRex UD384 (US$480) dropped into the mix micro-dynamic gymnastics went up several clicks. Not quite a smooth operator as the Redbook-only Synchro-Mesh, the UD384 can convert USB all the way up to 24/192 (as per the S/PDIF spec). More importantly, it allowed the aforementioned hi-res Bowie remaster to really come into its own. Its soundstage opened up in all directions – particularly width – and the windows through which the listener ‘observes’ the scene enjoyed a thorough Windex-ing. The KingRex box also adds a healthy dose of acoustic mass over and above the direct USB link.

    NAD’s own USB implementation is fine for casual listening or movie playback but readers are advised to spring for a USB-S/PDIF convertor if a computer is the main transport. The silver lining here is that the NAD’s USB socket is supplied via a slot-in modules. It can be upgraded as and when NAD release an upgraded board.

    To be continued…


    Associated Equipment

    • Squeezebox Touch
    • MacMini 2010 + MacPlatform
    • Empirical Audio Synchro-Mesh
    • KingRex UD384
    • Red Wine Audio Signature 15
    • Audion Sterling EL34
    • WLM La Scala


    Audition Music

    • Low – Things We Lost In The Fire (2001)
    • Billy Bragg – Don’t Try This At Home (1992)
    • Matthew Sweet – Altered Beast (1993)
    • Radiohead – Kid A (2000)
    • David Bowie – The Rise And Fall Of Ziggy Stardust And The Spiders From Mars (2012 remaster)


    Further Information

    John Darko

    Written by John Darko

    John currently lives in Berlin where creates videos and podcasts and pens written pieces for Darko.Audio. He has also contributed to 6moons, TONEAudio, AudioStream and Stereophile.

    Darko.Audio is a member of EISA.

    Follow John on YouTube or Instagram


    1. Excellent review of this very interesting piece of kit. I had the chance to borrow one for a weekend and posted my impressions here;

      I did not have the opportunity to compare the sound of the USB to SPDIF but overall I too approached the NAD with caution and low expectations and was stunned at how good it was for the cash.

      I haven’t pulled the trigger on it yet but expect to have one in the rack before Xmas.


    2. Interesting review. This technology is a pcm/pwm digital input amplifier just like Tact’s Equibit/TI Purepath driven amplifiers. The Tact Millennium MkI of 1998 considered to be the world’s first all digital amplifier, followed by the M2150 and S2150. Lyngdorf has also made similar amplifiers. The difference is the NAD amplifiers uses a different chip from Zetex rather than Tact/Lyngdorf and others using chips from TI. While Tact/Lyngdorf amps are entirely without any type of feedback, Zetex employs feedback. They could be construed as Power DACs.

    3. Hello john,

      thanks for your excellent review, which fully is in line with my personal experiences with this truly revolutionary product. Over the last 8 Months I have enjoyed every strong aspect of this new DAC/amplifying technology. The NAD C390DD has fully revived my ‘old’ watt-puppy 5.0 loudspeakers and MIT 750MH LS cables and Marantz / Tjoeb reference CD player. The speed and ‘grip’ on the woofers is astonishing compared to my former amplifier ( krell 300i ) as well as the liquidity in mid- and high-range. Soundstaging has improved in all aspects as well as dynamics, pace & rhythm. Both articulation and placing of voices and instruments are rock-solid, stable and tangible. The NAD C390DD achieves very impressive musical reproduction and totally distortion-free.
      The bass-management EQ works also excellent. With help of this DSP functionality, I have been able to neutralize the typical ‘ bump’ around 200 Hz in my room. So playing drum & bas guitar solo’s are a great pleasure. The huge damping factor this amplifier offers, totally controlls the low-range drivers of my speakers and the ‘slam’ factor experience is very much life-like and with such ease and speed, as if I am listening to 2 x 500W monoblocks (no kidding)

      I agree that listening to USB with the NAD C390DD is nit as impressive as with S/PDIF. I was also disappointed to find out that the applied USB is type 1.1 and not 2.0 Maybe NAD will come later with a MDC upgrade to USB 2.0 so playing HDtracks (24/192) will be possible as well

      But ther is a very interesting improvement I would like to advise you: Purchase and try a CANARE step-up transformer ( S/PDIF to AES/EBU) They only cost around 25 USD. Do not ask me why, but the improvement of digital playback is HUGE !! Much more than any other tweak I have tried over the last years…!

      For this reason, I have become interested to purchase a CD transport with ultra low jitter and AES/EBU output. Best would be a Olive like combination of a CD transport and network player, but they are too expensive. So hopefully NAD will come out with such a tool sooner or later 😉

      Looking much forward to the second part of your review!

      Warm regards form The Netherlands,

      Peter V.

    4. By the way John,

      You will experience also remnarkable differences when experimenting with power cables. I am very satisfied with my Jena Labs powercable:

      During reviews of the M2 overhere in The Netherlands, it was detected that the M2 suffers from using powerline conditioners… or othe power cleaning devices..! I have no personal experience with that, but will try out myself later on this year.

      All the best!

    5. Can someone tell me how the midrange of the 390DD stacks up to the midrange of the 375BEE? I hear great things about the bass of the 390DD but can the midrange keep the same pace? Thanks!

      • Sorry David – that won’t be me as I’ve not heard the 375BEE. Perhaps someone else can chime in?

      • Hi David,

        I totally agree that the midrange reproduction can make-or-break the tonal character of the amplifier. Rest assured – the NAD 390DD is a very convincing over achiever at all frequency levels. It sounds liquid, sweet detailled and dynamic. Especially with voices and piano recordings this is audible and pleasant.

        Due to the high resolution of this new amplifier technology, it will reveal mis-matches in loudspeaker – cables and source faster than with other Class A or B or tube amps. So at the end it is ( as always) a matter of listening for yourself, preferably with your own set at home.

        Beside John Darko’s review you can enjoy Robert Harley’s ( TAS 224) review as well – now free-of-charge !

        Good luck and happy listening!

        – PeterV-

      • I spent just three (long)days listening to the 390DD so my opinion may not be the definitive view but I thought it performed superbly across bass, midrange and everything else. Indeed no particular character or quirk stood out at all. The 390DD just seemed to inhale each challenge – orchestra, solo piano, rock, jazz, dub step with a calmness and an unflustered ease that just begs you to throw it a new challenge. Throughout it all it remains totally focused,tack sharp and detailed.

        Rather than present music with the self conscious flourish of a waiter presenting a beautiful dish the NAD just shine a clear natural light on a smorgasbord of delights and invites to help yourself.

        Great piece of kit that IMHO suddenly makes many amps sound like they really are trying way too hard to impress as they strain to conceal their limitations.

    6. Hi, thanks for the replies. Actually, the point you bring up about hearing it myself is an interesting one. It seems there are no more NAD dealers in my area since NAD decided to go online with sites like Audio Advisor and others. So, hearing it myself is no longer practical. As for the Robert Harley review, that’s the review that got me wondering because he loves the bass but never really says much about the midrange or highs. As a matter of fact, he even mentions that one could find other integrated amps in the same price point as the 390DD that have a better midrange. That review says more for what he left out than what he said. And in this day and age, unless your speakers are full range, and I mean well into the 20’s, what good is an amp that excels at bass – especially with all the great subs that about these days (e.g. REL). It’s times like this that I’m reminded that life is mostly about grey areas…absolutes, well, not so much…

      • Hi David,

        It is really a shame that you are unable to do your personal review . This would be indeed the only objective and un-biased way to define yourself if the NAD C390DD in combination with you loudspeakers, cables and source and acoustical environment would be ‘ your cup if tea’

        Although I might be a bit over-enthousiastic ( and with that not neutral anymore 😉 you have to admit that new developments like this NAD with Zetex amplifier technology and the impressive specifications at this price level are interesting.

        But I fully agree that even ‘revolutionary’ will not impress if there is no perfect match with other components. On top of this we always have to accept that long-term listening experience to Class A , A-B or tube amplifiers and changing speaker designs etc. will influence our taste and tolerance for what we find attractive or not. It migh just be that the most neutral and high-end audio system money can buy, will also not appeal to everyone…

        So, my personal belief and large part of our hobby and passion is actually the quest how to achive the optimum balance between taste, components and budget. Chasing this goal is what keeps us audiophiles running and when one reaches a small step towards improvement at acceptable price levels it is funny to notice how easy we are able to enjoy our music!

        All the best!


      • Hi. David, on your comment from Sept.5th, you mentioned RH’s review from TAS. I take his review with a grain of salt for the following reason: I have read his review a few times (I’m a subscriber), and it is clear that he never tried the S/PDIF input. He only tested the USB input. Why? I don’t know. I guess even the best miss stuff sometimes. If you look at JD’s review above, his comparison of the USB and S/PDIF inputs fits RH’s observations with the USB. Same with PeterV’s comments. The best bet is to order it from Audio Advisor and hear it out for yourself. When I add a second system to my living room, I am considering matching up the C390DD with Anthony Gallo’s Classico CL-4 (source will be iMAC or Air with a to-be-determined USB->S/PDIF converter). Cables may be tricky, but I’ll use the cable library from The Cable Company to figure out what speaker cables will work best.

    7. Does anyone have any comments about how the 390DD stacks up against the NAD M51 Dac/Preamp? I’m debating buying the 390DD vs the M51 running into my NAD 356BEE – bypassing the 356’s preamp. So many decisions, so little time….HELP!!!

      • On the NADelectronics website you will find a review which might provide you some reflection:

        The C 390DD is a great amp. My old amp was the C 356BEE, so that is my reference, loudspeakers are the Naim Ovator S-400. The 390DD offers a lot more detail, the presentation is “calmer” and there is no noise. The amp controlls the loudspeaker pretty good, the sound is powerfull when necessary but not overexcited. Even on low volume there is lots of detail to listen to. Even if i was already pretty satisfied with the C 356BEE, i had the feeling that my loudspeakers had more possibilities. The C 390DD was a big step up, the sound is very pleasing and neutral, so this amp will probably be my amp of choice for a long time. Some minor issues: So far, i could not figure out, how to connect my headphones. I connected the headphone amp to the preamp out, but i can’t find a way, to turn the speakers mute. When playing music via usb-stick (front) with the CD-Player C 565BEE i am able to control the usb-stick via the remote of the cd-player, with the C 390DD i can choose which file to play, but i can’t start, stop or skip with the remote. The new C 390DD remote control does not handle the cd-player anymore, so now i have to use 2 remotes again.

        Gunnar A – Germany

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