The NAD C399 is an integrated amplifier from the Classic series, delivering 180 watts per channel. It incorporates technologies from the Masters series while retaining an essential-focused design, characteristic of the brand since its creation in 1972. Its digital architecture includes a high-resolution DAC, and it is designed to deliver high performance in an integrated format.
At the heart of the C399 lies the Hypex HybridDigital nCore amplification module, a technology representing the culmination of decades of research in digital amplification. Contrary to common misconceptions about Class D, this architecture surpasses traditional linear amplifiers in every measurable parameter while preserving the musical qualities sought by music lovers.
The nCore module operates on a controlled 5th-order self-oscillation principle, without hysteresis, with a feedback loop taken exclusively from the speaker output. This approach ensures perfect adaptation to the actual load, regardless of the impedance of the connected speaker. The damping factor, greater than 150 up to 6.5 kHz, ensures firm control of the drivers, particularly beneficial in the bass range.
NAD does not simply integrate the standard Hypex module. The company holds a special license allowing it to directly oversee manufacturing according to its own specifications. The switching power supply, designed specifically by NAD, replaces the usual Hypex power supply. This customization results in increased stability with difficult loads and an impressive instantaneous current reserve: more than 26 amps into 1 ohm for 1 millisecond.
Total harmonic distortion remains below 0.02% across the entire audio band, dominated by 2nd- and 3rd-order harmonics, perceived as musically consonant. The signal-to-noise ratio exceeds 106 dB, pushing any background noise below audibility, even with high-efficiency speakers.
The ESS Sabre ES9028 32-bit digital-to-analog converter is a wise choice for the C399. This chip, identical to the one used in the Masters M10 and M33 models, offers exceptional resolution up to 384 kHz. More than a simple numbers race, this capability ensures uncompromising conversion of current and future high-resolution formats.
Jitter management, the bane of digital systems that blurs timing accuracy, reaches negligible levels here. Measurements reveal remarkable clock stability, preserving spatial coherence and the natural character of timbres. The four S/PDIF inputs (two coaxial and two optical) accept signals up to 24-bit/192 kHz, more than covering domestic needs.
The HDMI eARC input deserves special mention. This interface, still rare on stereo amplifiers, enables seamless integration with modern televisions. The sound from films and series thus benefits from the C399’s audio quality, without multiplying remote controls or cabling complications.
The C399’s moving-magnet phono stage exceeds the usual expectations for an integrated unit. Based on NAD’s standalone PP2e preamplifier, it incorporates several patented innovations. The extremely accurate RIAA curve faithfully restores the tonal balance engraved in the grooves. The exceptionally high signal-to-noise ratio preserves the subtlest nuances.
One distinctive feature is the infrasonic suppression circuit. This function, absent from many high-end preamplifiers, eliminates parasitic frequencies below 20 Hz generated by warped records and mechanical resonances. Unlike traditional high-pass filters that affect audible bass, the NAD solution preserves the extension and dynamics of musical low frequencies.
The generous overload margin accommodates high-level pressings without clipping. Coupling capacitors, selected for their sonic neutrality, preserve the signature of each cartridge. The standardized input impedance ensures optimal compatibility with the majority of MM cartridges on the market.
Modular Design Construction technology, introduced by NAD in 2007, reaches its second generation with the C399. The two MDC2 slots on the rear radically transform upgrade possibilities. Unlike the first generation, limited to one-way updates, MDC2 enables bidirectional communication between the module and amplifier.
The BluOS-D module perfectly illustrates this potential. Beyond high-resolution streaming up to 24-bit/192 kHz via Wi-Fi or Ethernet, it provides Dirac Live room correction. This function analyzes the acoustics of the listening room using a supplied calibrated microphone, then applies custom-calculated corrections. Room modes, those resonances that color the bass, are neutralized without affecting the natural character of the musical signal.
The bidirectionality of MDC2 fully demonstrates its relevance here: Dirac Live applies to all sources connected to the C399, digital as well as analog. Five storable profiles allow the correction to be adapted according to the listening position or room condition (curtains open or closed, for example).
BluOS also transforms the C399 into part of a sophisticated multi-room ecosystem. The control app, available on all platforms, provides access to more than twenty streaming services, several of which offer lossless and high-resolution streams. Native compatibility with Spotify Connect, Tidal Connect and Apple AirPlay 2 simplifies integration into existing digital environments.
The connection section reveals in-depth consideration of contemporary uses. The two pairs of RCA line inputs use low-noise buffer stages, preserving the integrity of analog signals. Preamp outputs allow the addition of an external power amplifier or the supply of a multi-zone system.
The two independent subwoofer outputs facilitate the integration of subwoofers, with the possibility of optimizing their placement without cabling constraints. This attention to practical details characterizes NAD’s approach: technology in the service of the user, never the reverse.
Bidirectional aptX HD Bluetooth deserves to be highlighted. Beyond high-quality reception from mobile devices, transmission to Bluetooth headphones preserves audio quality. This feature, rare on integrated amplifiers, responds to new wireless listening habits.
The dedicated headphone amplifier, far from being a last-minute addition, delivers comfortable power even for high-impedance studio headphones. The optimized output impedance ensures a linear response with the most demanding multi-driver in-ear monitors.
90 dB at 1 kHz
75 dB at 10 kHz
Modern electronic components require little break-in. Nevertheless, about a hundred hours of use allows the capacitors to stabilize and the power supply to reach optimal performance. The differences remain subtle compared to tube amplifiers.
The basic C399 offers all amplification and conversion functions. The BluOS-D module adds network streaming, multiroom compatibility, and Dirac Live room correction. Installing the module is simple and reversible, and can be done later.
nCore amplification objectively surpasses class AB in all measurable parameters: distortion, noise, bandwidth, stability with complex loads. Subjectively, it preserves musicality while providing control and transparency. Prejudices about the “coldness” of class D do not apply to this generation.
The C399 only includes a preamplifier for moving magnet (MM) cartridges. Users of MC cartridges will need to add an external preamplifier or step-up transformer. This limitation allows performance to be optimized for the majority of users.
Dirac Live analyzes your room’s acoustic response via a series of microphone measurements. A sophisticated algorithm then calculates correction filters uploaded to the module. The standard correction operates up to 500 Hz, the critical zone for room modes. An optional license extends correction to the entire audio band.
The energy efficiency of class D greatly limits heat dissipation. The C399 remains warm even after hours of high-level listening, allowing installation in confined spaces that would be impossible with an equivalent power class AB amplifier.
Based on reviews from customers who purchased this product, summarised by AI
Jean-Marc
It's entirely personal, but I didn't like the sound signature of this amp.
Comment from August 28, 2026 — Experience from October 07, 2024
Peter
Very good amplifier! Good store, with good service. Ran into an issue with an item that was backordered, and I got my money back without any problems. But very satisfied with my purchase of the NAD c399.
Comment from July 22, 2026 — Experience from June 19, 2026
Olivier
Built like a tank. Superb finish. Top-notch sound quality.
Comment from February 25, 2025 — Experience from June 15, 2023
