NAD C 399 Hybrid Digital DAC Amplifier Review

NAD’s C 399 Hybrid Digital DAC Amplifier is built with trickle-down tech from the acclaimed Masters Series. With the same ESS Sabre DAC as the premium M10 and M33 amps and Hybrid Digital Hypex nCore circuitry, it brings high-end sound to an affordable price point. Modular Design Construction means you can add features as you wish to bring in things like BluOS, AirPlay, and Dirac Live room correction.

• Two-channel integrated amplifier with ESS Sabre 32-bit/384kHz DAC
• Two Modular Design Construction expansion slots
• MDC2 Module adds BluOS, streaming, and Dirac Live capabilities
• 180 watts per channel continuous, 250 watts peak
• Moving-magnet phono stage
• HDMI eARC input
• Two pairs of speaker outputs
• Two sub outputs

Since its founding in 1972, NAD (New Acoustic Dimension) has represented high-end sound at a reasonable cost. It first came to the attention of audiophiles in 1978 with the now-legendary 3020 Integrated Amplifier. I had one of these in college and it was my first serious audio component. And I could afford it which is no small thing when you’re 18 and living in a dorm in Boston.

Today’s NAD amplifiers have leveraged the latest in Class D technology and over the past 10 years, they have not rested in their pursuit of better sound while keeping the price of admission in check. A perfect example is the new C 399 Hybrid Digital DAC Amplifier. Its internals are directly tied to the high-end Masters Series M10 and M33 amplifiers. Not only does it share those products’ ESS Sabre DAC (9028) with 32-bit/384kHz resolution, but it also uses the same Hybrid Digital Hypex nCore amplifier circuitry found in the M22 Stereo Power Amplifier.

To this, NAD has added Modular Design Construction (MDC) which allows expansion boards to be installed that add or upgrade features. The C 399 has two slots, and my review sample was already populated with the MDC2 BluOS-D Module that adds BluOS, AirPlay 2, Spotify Connect, Tidal Connect, and Dirac Live room correction. The best part? The C 399 starts at $1,999 with an additional $549 for the BluOS module. That’s about half the price of an M33. Exciting is hardly a strong enough adjective. Let’s take a look.

• NAD Masters M33 BluOS® Streaming DAC Amplifier Review
• NAD Masters M28 Seven Channel Power Amplifier Review

NAD has always been about the delivery of efficient and honest power and the C 399 embodies that mantra. It’s rated for 180 continuous watts, both channels driven, with peaks up to 250 watts. I had no doubt of this as I could drive my 4-ohm Axiom LFR-1100 speakers to high levels without audible distortion. The C 399 is more than stout enough to drive any speakers you wish to use well beyond room-filling volumes.

This is all done coolly and efficiently by Hypex nCore amplifier circuitry. It’s known for wide bandwidth, flat frequency response, and high current capability, and it certainly delivers. NAD has been using this technology for a while and it seems with each new product, the sound gets better and better. My initial impressions were very favorable. The C 399, like all the NAD amps and receivers I’ve reviewed, is unfailingly neutral and finely detailed.

The DAC section is anchored by an ESS Sabre 9028 chip capable of up to 32-bit/384kHz sampling. In the C 399, the sample rate is capped at 24-bit/192kHz. Obviously, this applies only to the digital inputs in the amp’s default configuration but if you add the MDC2 BluOS-D module to one of the MDC slots, you can enjoy this excellent DAC for your streamed content as well. My review sample had this card already installed so I could hear my library of Apple lossless rips in full detail. Adding BluOS lets you integrate the C 399 into the BluOS ecosystem which can be any number and combination of players, amps, and speakers, managed in multiple zones. The module also adds Dirac Live room correction. With the free software downloaded from NAD’s website, one can apply correction to the range of 20-500Hz.

In front, the C 399 sports NAD’s simple and clean styling with a power button at the left followed by a menu nav pad, quarter-inch headphone jack, and an info display in the center. The screen has decent resolution but it’s borderline too small to be read from more than about eight feet away. When streaming, it shows the song title, volume level, and source. To its right are input toggle keys and a large volume dial that moves in 0.5dB increments.

In the back, there are two coax and two optical digital inputs plus HDMI w/eARC. If you have the MDC2 BluOS-D module, it adds USB plus streaming via RJ-45 cable or Wi-Fi and Dirac Live room correction. Analog inputs include two stereo RCA and moving-magnet phono. There’s an RCA pre-out and two subwoofer outputs as well. For control, you can employ IR in/out, 12v trigger in/out jacks, and RS-232 which interfaces with systems like Control4, Crestron, and the like.

My C 399 sample came with the MDC2 BluOS module already installed. Its box includes a puck-style microphone for Dirac Live and two antennas. The free version of Dirac allows correction up to 500Hz, but I had a license for the full package from a previous review, so I tried three different configurations, tight focus, normal focus, and normal focus limited to 500Hz.

For the review, I used only the two Axiom LFR-1100 speakers at the front of my room and only used the front baffles. Running them omnidirectionally requires a DSP placed between the pre-amp and power amp, so in effect, I turned them into M100s. They are 4 ohms nominal with 93dB (1w/1m) sensitivity. They’re not too hard to drive but when the volume is turned up, they will generate some amplifier heat. Not so this time, the C 399 runs super cool. Listening for over an hour at high levels sent temps just a few degrees above ambient.

With the speakers connected, I set up the C 399 as a BluOS player using my trusty app. It took just a few minutes to bind the amp to my Wi-Fi network, then I could use it as an AirPlay device. With my entire iTunes library consisting of lossless CD rips, I don’t need to sling discs anymore which is super convenient. I checked out a few tracks to make sure everything was working, then turned to Dirac Live.

I have something of a roller-coaster relationship with room correction. For many years, I used Audyssey with an Integra DHC 80.1 processor and was very happy with its sound for movies, but I felt it was too flat for music. Recently, I put an Anthem AVM 70 in my system. I liked the sound of Anthem Room Correction (ARC) very much, but I decided I would give it a few weeks with no correction to see how I liked it. After a few tweaks of the channel levels and a few weeks of listening, I decided I preferred the uncorrected sound. Yes, it has a mode right around 50Hz but in time, I found I liked the more forward bass presentation and most importantly, the deeper soundstage. My old recordings suddenly had more life and realism. So, with these things in mind, I spent some time exploring the Dirac software.

Dirac first has the user set speaker levels in the software before proceeding with measurements. I set them at around -25dB. Then, you get the choice of three sound stage sizes, tight focus, normal focus, and wide focus. Since my room is relatively small, I started with tight which requires nine measurements around the listening position. The app shows a graphical representation of where one should put the mic so it’s super easy to run.

The result was very balanced from a frequency standpoint and was indeed very tightly focused. It shrunk the music down to a space no wider than the speakers. It wasn’t for me, so I went for normal which sounded just right from a room versus sound stage perspective. But I found the high range lacked depth and I could see why on the computer screen. Dirac had cut some slight peaks around 6kHz and created a gradual slide from bottom to top of around 5dB.

I decided to create a configuration that stopped at 500Hz to simulate what a user of the free software would experience. This was my favorite configuration of all. It smoothed out the bass by removing that 50Hz bump and that’s all. The soundstage retained its natural depth and width. I listened to this version for a few days, then spent the same amount of time with Dirac turned off. Ultimately, I preferred the music without correction. This is no slight on Dirac Live, it’s an excellent system and I’m sure with more experimentation, I could achieve even better results. But I’ve really become accustomed to my house curve.

My conclusion from this part of the exercise is this: Dirac is a very powerful and capable room correction system. But not all rooms need correcting. My room is isolated and well-treated with sound absorption and diffuser materials. Its bass mode is minor, and I only have two seats. If your room has more issues like openings to other rooms or an odd shape or more seats, you will likely benefit from Dirac.

All comments here are with Dirac Live turned off. Though I found a happy medium by restricting it to 500Hz, I still preferred my room’s natural tendencies. And the C 399 has an incredibly balanced and neutral presentation. In my space, it doesn’t need any help to sound great.

The first thing I noticed is the noise floor – as in, there isn’t one. This is the quietest integrated amp I’ve yet heard. Even the superb M28 multi-channel amp I reviewed a while back had an audible noise floor. Previous Hypex-based NAD products I’ve reviewed also had audible noise when no signal was present. The C 399 has somehow eliminated this.

When listening to Foo Fighters Skin and Bones live performance, I heard some faint hiss during the quiet sections. This did not come from the C 399 but rather the band’s on-stage amps and monitors. Listening to more processed recordings confirmed this. The complete absence of a noise floor means ambient details in the music like guitar string squeaks or the creak of a chair pop right out. It really adds to the realism of the moment.

Dave Grohl’s voice was presented in its varied characters which range from a smooth tenor to guttural screams. “The Best of You” is a prime example. If you turn the volume high enough, it’s as if he’s singing right into your ear. Yet the background music is crystal clear. This is a well-engineered recording, and the C 399 presents it perfectly.

Van Halen’s inaugural album of the same name is a perfect example of 1970s rock recording, no dynamic range, and lots of guitar distortion. It’s a great album to be sure but finesse and detail were clearly not a priority for the sound engineers of the day. Nevertheless, “Eruption” shows plenty of percussive detail as Eddie taps and picks through this legendary solo. Though there is only one dynamic, LOUD, I could still hear the subtle differences in his techniques as he explores the limits of the guitar. The previous track, “Runnin’ With The Devil”, features a low bass solo that clearly demonstrates the C 399’s ability to play absolutely everything present on the original recording. You can easily hear the strings flopping into each other as Michael Anthony plucks them.

My recent obsession with Jacqueline Du Pré led a good friend to loan me his three-CD set of her Favourite Cello Concertos which includes all the greats, Dvorak, Elgar, St. Saëns, Haydn, and others. Her bright lively sound really played to the C 399’s strengths. This recording is what led me to listen without room correction. I just didn’t want to touch the shimmering high partials in her tone. It’s interesting to note that she is playing on the same instrument that Yo-yo Ma uses in his recording of Bach’s Cello Suites. Her technique, and likely her choice of bow, make that cello sound much livelier with an ethereal singing quality.

On a completely different tack, the Concerto for Bassoon by Andre Jolivet, masterfully played by Sergio Azzolini, just came alive from the C 399. This work is loaded with fantastically difficult techniques for the soloist to overcome but when played successfully, it sparkles. Inspired by jazz, Jolivet pushes the instrument to its physical limits. Azzolini brings a loose and almost improvisational character to his performance and it is my favorite rendition of the piece. The balance of massed strings, harp, and piano was perfectly rendered as was the slight reverb of the hall where the recording was made.

This same reverberant quality was clearly audible in Gubaidulina’s Duo Sonata for Two Bassoons. Valeri Popov and his protégé explore many extended techniques in this 10-minute work which was obviously recorded in a very live recital hall. The C 399 had no trouble presenting every multiphonic, flutter tongue, and quarter-tone in this piece which still sounds relative today even though it’s from 1977.

I also enjoyed Eric Stomberg’s bassooning in his recording of Jennifer Higdon’s Dark Wood for bassoon, cello, violin, and piano. The C 399 is a real chamber music powerhouse as it clearly distinguishes each instrument. If the recording is properly mixed as this one is, you can close your eyes and see where each player is on the stage.

The NAD C 399 HYBRID DIGITAL DAC AMPLIFIER brings reference level performance to a reasonable price point. It runs with the big dogs for about half the cost.

There is truly nothing I can complain about here. The NAD C 399 is by far the best integrated amplifier I’ve heard at this price point. With the BluOS module installed, it delivers nearly everything that the Masters M33 does for half the price. Some may complain that you need to add on $549 for the module but that’s still just $2,548. How can you go wrong? And the module adds full streaming capability which is something we’re finding in a lot more stereo amps today.

Though I found Dirac Live completely competent in its free version, I still preferred the sound with it turned off. And rather than spending the $99 on the full software package right away, I urge buyers to experiment with Dirac limited to 500Hz. If your room is reasonably well treated, the C 399 delivers smooth and balanced sound on its own.

With NAD’s usual efficient design, the C 399 is a great match for just about any speakers you care to use. Big towers, detailed bookshelves, electrostats; I doubt there is anything this amp can’t drive. If you have around $2,500 in your amplifier budget, I urge you to check it out.