Secrets of Home Theater and High Fidelity - Best Of Awards 2015

NAD C 510 Direct Digital Preamp DAC Review Highlights

Is your trusty old stereo setup looking for a minor makeover? Are you wanting to play more of those high resolution audio files from your computer or Blu-ray player through to your big speakers and revel in all the high bitrate sonic goodness? Boasting high speed digital processing and HDMI connectivity, the NAD C 510 aims to bring your traditional two channel music system into the twenty-first century.

Based on a similar concept as the well regarded M51 Direct Digital DAC in NAD’s Master Series line, the C 510 wears a more traditional looking NAD suit. And in some ways, more than the Master Series, it reflects NAD’s traditional values and reputation more clearly, which is a simple understated design with absurdly capable real world performance.

In my two channel stereo setup the C 510 made a welcome and noticeable improvement to my musical enjoyment and opened up some additional connection possibilities that I, up to this point, had not yet explored.

NAD C 510 Direct Digital Preamp DAC Review

NAD C 510 Direct Digital Preamp DAC Highlights Summary

  • Exclusive use of the CSRA6601 chip as a DAC
  • Incredibly detailed and well resolved sound, without sounding lean or etched
  • Can be used as a standalone DAC or as a digital preamp with volume control (digital domain)
  • HDMI connectivity and video pass through
  • Single ended and balanced outputs
  • Will not decode native DSD bit stream directly

Introduction to the NAD C 510 Direct Digital Preamp DAC Review

During my first ever trip to CES in January, 2015, one of the things I noticed, while auditioning the various audio related rooms and booths at the Venetian Hotel, was the crazy number of DACs that are now out there on the market. Maybe I’ve been under a rock for the past little while, but I don’t recall DACs being so talked about and hyped since about 15 to 20 years ago. At that time the discussion was about how inadequate the decoding in your standalone CD player was and how this extra little “black box” would bring back all the missing life to the digits on your little silver discs.


  • Design: Converts PCM to PWM via exclusive CSRA6601 chip
  • Resamples at 108 MHz; Converts to PWM at 844 kHz, 35-Bit
  • Signal to Noise Ratio: -123 dB (ref. 0dBFS 2V out)
  • Digital Inputs: XLR, Coax, Toslink Optical, USB, 2 x HDMI
  • Analog Outputs: One Pair XLR, One Pair RCA
  • Other Connections: HDMI Video Out, RS232, 12V Trigger In and Out, Upgrade Jack
  • Dimensions: 4″ H x 17″ W x 12″ D
  • Weight: 10.4 Pounds
  • MSRP: $1,299.99 USA
  • NAD

As the years went on, CD players got progressively better, focus shifted more towards home theater, and with the progressive advancements of portable audio and the arrival of the MP3 format, I think the subject of DACs became more of a concern for the committed and, more often than not, well-heeled audio enthusiast.

Fast forward to today: high resolution audio files are now available for download, while storage media has increased in size and has become much more affordable. The idea of streaming your media around the house in the best quality possible is a very doable proposition. Also, computer audio, as a serious method of musical enjoyment, has come of age, and audiophile media such as high resolution Blu-Ray audio is becoming more prevalent.

I mean, serious on-the-go audiophiles are buying portable DACs the size of their mobile phones to carry along with them, strapping them to their players with rubber bands! If ever there was a time where a digital hub of “sonic awesomeness” was needed to make all your (at home) media sound its best, it is NOW. Enter the NAD C 510.


The Design of the NAD C 510 Direct Digital Preamp DAC

NAD C 510 Direct Digital Preamp DAC Review

DACs (Digital to Analog Converters) are typically meant to do one job. That is, take the digital information from a given transport medium and reassemble said information into a pristine analog waveform. That waveform will eventually be amplified to come out of our speakers as music, reach our ears and, hopefully, be able to move us in the intended way.

From a circuit design standpoint, most DACs, save for some of the more esoteric models, will usually start with a main converter chip sourced from an established manufacturer. Those chip makers tend to be one of the following: Analog Devices, AKM, Burr-Brown, Cirrus Logic, ESS and Wolfson.

Once a digital core has been selected, the surrounding electronics such as the power supplies and the analog components are then developed and honed to maximize the core chip’s potential performance.

When Secrets Editor-in-Chief, Dr. John Johnson reviewed the NAD M51 Direct digital DAC back in 2012.

(he noted how NAD had gone the unusual route of designing a custom decoding solution instead of starting off with a ready-made chip to design around. The core chip in question is the CSRA6601 and was co-developed with Zetex Semiconductor (the technology is now owned by Cambridge Silicon Radio) and was originally part of a chipset produced for switching power amplifiers. In this case, part of that original chipset has been repurposed for use solely as a DAC chip.

NAD C 510 Direct Digital Preamp DAC Review NAD C 510 Direct Digital Preamp DAC Review NAD C 510 Direct Digital Preamp DAC Review NAD C 510 Direct Digital Preamp DAC Review

Visually, the NAD C 510 eschews the brushed metal look of the well regarded Master Series line for the more traditional minimalist look of NAD components of yore. There are less hard corners and more rounded edges nowadays, but the NAD look is unmistakable. The front panel is very simple and straightforward with a blue dot matrix display taking up a fair share of the face.

NAD C 510 Direct Digital Preamp DAC Review

The display clearly spells out which input is in use and the sample rate that the input is being fed. Basic settings options and selections are visible through the display as well. Moving a little to the right we find a pair of buttons that are used to cycle through the various inputs. Moving to the right some more, we encounter a rotary dial that operates the digital volume control. The volume can be set to a user defined fixed level for DAC use or a variable level, so the C 510 can operate as a digital preamp. Lastly, the power button is located on the far left.

NAD C 510 Direct Digital Preamp DAC Review NAD C 510 Direct Digital Preamp DAC Review

On the back side, from left to right, we have both balanced and single ended analog outputs, an AES, a coaxial and an optical digital input, followed by a USB input for computer hookup. The next two inputs are a rare sight on an audio only component, but I think will start being more prevalent in years to come, those being a pair of HDMI inputs. An HDMI output comes next, allowing unmolested video pass-thorough to a display device. A USB socket marked “Upgrade” is next, presumably used for firmware updates and the like. Lastly there is an RS 232 serial port that is AMX and Creston compatible, a 12 volt In and Out trigger jack and an IR extender jack.

NAD C 510 Direct Digital Preamp DAC Review

The remote control provided with the C 510 is an all plastic unit that is nicely weighted and feels good in hand. It’s got all the control buttons you would expect for an audio preamp, plus learning capability to control up to three other components comfortably. Pressing the DIM button allows the DAC’s front display to be turned off and then a choice from 5 levels of intensity. Nice! Positive and reverse polarity selections are also available along with adjustment of the fixed volume level through the Setup menu.

Out of the box, the C 510 had a fixed volume level of -20 dB. For my listening, I adjusted the fixed volume level to -3 dB to, more or less, match the incoming level of a couple of other DACs and CD players I had on hand. This allowed me to have multiple units hooked through my preamp, with the ability to switch between sources, playing back the same material, with just the turn of a dial.


Setup of the NAD C 510 Direct Digital Preamp DAC

For the majority of my testing, I had the C 510 hooked up to my two channel system, serving primarily as a DAC. I did experiment a little with it as a preamp, using the adjustable volume, and while it works quite well as advertised, it was just more practical in my setup functioning in pure DAC mode, adjusting the master volume via my existing preamp. I had also just obtained a new OPPO BDP-103 universal player for Christmas and it allowed me to make good use of the C 510’s HDMI inputs.

As a matter of fact, the new player never made it into its intended spot in my home theater. So convenient and good sounding was the pairing of the OPPO with the NAD that it may never leave my studio! The OPPO allowed me to hook up an external USB hard drive full of music files, and access them with a simple and quick navigation menu on my studio TV. It was a much better solution than the old Western Digital media player that I had been using previously.

Associated equipment in the review: OPPO BDP-103 Universal player, Onkyo DV-SP1000 universal player, Bryston BP 25 preamplifier, Marchand XM 16 electronic crossover, Marchand BASSIS parametric equalizer, 2 Carver TFM 55x power amplifiers, BESL (now Bamberg Audio) Series 2 MTM monitor speakers, twin custom sealed subwoofers with 15 inch Dayton Reference HF drivers.


The NAD C 510 Direct Digital Preamp DAC In Use

I’m just going to say up front that I really like the sound of the NAD C 510. Besides the fact that it’s just neat to see a company go in a different direction when designing a piece of core audio gear, I think that in NAD’s case, it’s paid some sonic dividends, resulting in a very stellar sounding component. Through my comparisons with other DACs and other players I had on hand, the NAD revealed itself to be a very honest and transparent reproducer of sound.

Its ability to mine every last little bit of detail from my collection of spinning silver platters and hard drives was very, very impressive. I found myself noticing more details and subtleties in songs that I’ve heard countless times, and I found that I could listen at louder volumes more cleanly with the NAD in my system.

For myself, with other DACs and players that I’ve used, there has always been a “ceiling” where the music isn’t uncomfortably loud, but it becomes uncomfortable to listen to for an extended period, meaning too much distortion. The NAD sounded better and better to me, the louder I turned it up. Don’t get me wrong, it sounds perfectly great puttering around at low volumes as well, but wide open and at full “chat”, the C 510 just sings!

There are two other standalone solid state DACs that I’ve used in my system regularly over the past couple of years. One is the Audio GD Compass 2 based on the ESS Sabre 9018 chip, and the other, an ONIX DAC 25 based on the Texas Instruments PCM 1792 chip. I did some comparisons where I had the NAD and the two other DACs hooked up simultaneously through the various digital outputs (HDMI, optical and coaxial) on my OPPO player, and I would simply switch between preamp inputs to compare the same musical track.

Again, the NAD’s adjustable digital volume made it easy to equalize its output levels to the other DACs which were about identical to each other. A few other times I compared the NAD to each of the other DACs individually with the OPPO hooked to the C 510 with either the coaxial or the optical input.

Some of the music I listened to during my stint with the NAD:

NAD C 510 Direct Digital Preamp DAC Review

“Rhythm and Blues” by Buddy Guy on CD is excellent recent vintage recording of a Chicago blues institution. Buddy Guy is in top form on this two CD set, and the C 510 helped to present a nice big soundstage and reproduced the boldness and power of his electric guitar with accuracy and detail to spare. This was one of those recordings that I expected to get harsh and fatiguing when I turned up the volume but, thankfully, no such thing happened. There was no edginess to speak of on any of the guitar or background horns, just clean, dynamic reproduction. Buddy’s voice came through with plenty of character, particularly on the more intimate tracks, while cymbals had just the right sheen to their sound, and bass delivery was tight and solid. The other two DACs did an admirable job with this CD set as well, but, in general, I felt the NAD gave me a cleaner presentation overall.

NAD C 510 Direct Digital Preamp DAC Review

Steely Dan’s Pretzel Logic on Japanese import SACD is an excellent edition of this classic recording. It’s also one of the discs that I found sounded a little “tubby” when listening through the other DACs I had on hand. In particular, I felt the electric piano and drums sounded like they had too much upper bass, making the songs seem heavy and congested. This was not the case when playback was happening through the NAD. The C 510 brought out a level of clarity and detail that made all the music lighter and more “alive” sounding. Its sonic presentation also befitted the scrupulous production values that Steely Dan had put into those original recordings in the first place. The NAD C 510 does not natively decode DSD, so I needed to set my OPPO BDP-103 to convert the DSD bit stream to PCM before passing it along. The NAD accepted this at an indicated, down sampled, rate of 88.2 kHz. Having just experienced the plethora of DACs at CES, many of which touted their ability to decode native DSD (mostly though USB inputs), I inquired to Greg Stidsen, the Director of Technology and Product Planning for Lenbrook International, why the C 510 did not have this ability? He replied to me,

“Regarding ‘why no DSD’, when the DDFA part was in development, DSD was dead, dead, dead. We were ‘giving away’ SACD players at steep discounts at the time. Nobody wanted them. Now, if you have an SACD player that supports HDMI (like Oppo) you can play SACDs with the C 510 via HDMI (DSD converted to encrypted PCM). But the USB input does not support DSD streaming, unfortunately.”

The NAD does have the ability to be updated via firmware, but I received no indication as to whether native DSD decoding could be in a future update, or if it would be even possible at all with the current hardware inside.

NAD C 510 Direct Digital Preamp DAC Review

“The Crossing” by David Elias is a direct to DSD recorded album done by the independent folk artist. The entire album consists of downloaded DSF files, available both in stereo and 5.1 surround. The files were played through the OPPO from a connected external USB hard drive and decoded by the NAD as 88.2 kHz PCM.

There is a vigorous debate going on out there as to the value of DSD as a recording medium versus PCM. Is there a discernible increase in sound quality with DSD, or is it just hype and are all these DACs that can decode native DSD just jumping on this latest bandwagon? A lot of this stems from the confusion of what exactly constitutes “Hi-Res” music these days and if we, as the consumers of it, know exactly what we are really getting, quality-wise, when we click the “purchase” button on various music sites.

From my perspective, the quality of the musical production (recording, mixing, mastering) makes far more difference to the final outcome than the delivery format itself. “The Crossing” is some of the most wonderfully recorded music that I’ve ever heard, folk or otherwise, and the NAD just rendered all the instrumental and vocal nuances about as perfectly as I could have wished, even at the down-sampled, encrypted rate I was getting.

NAD C 510 Direct Digital Preamp DAC Review

The Very Best of Erich Kunzel and The Cincinnati Pops “Top 20” on CD by Telarc. This is an old standby for sheer musical dynamics. Telarc, as a label, cut its teeth making modern recordings that pushed the limits of what the compact disc format and your stereo set could reproduce. On less capable equipment, this CD will sound shrill and grating on a number of tracks. The dynamic musical swings will not get translated properly. Not so with the C 510. This album came across the best I have ever heard it. As I turned up the volume, the entire orchestra just became positively massive! Huge soundstage and all the instrument sections were easily discernible. Strings in particular had a lovely, smooth, yet detailed presentation. Bass, on a number of the tracks taken from sci-fi movies, was as powerful as all get out and it actually frightened my dogs!

In general, over the course of my audition time, the subjective impressions I came away with were that the ONIX DAC 25 added a little bit of a euphonic quality or “bloom” to music, similar to what people associate with a “tube-like” sound. This resulted in certain tracks sounding like they had an extra sense of space. The Audio GD DAC, by comparison, had a slightly more detailed sound but with a little bit of an accentuated upper bass that I noticed more readily on rock and electric blues music. The NAD, in turn, was very even handed with all manner of music that I threw at it. The C 510 sounded impeccably clean with no trace of noise that I could discern.


Conclusions about the NAD C 510 Direct Digital Preamp DAC

NAD C 510 Direct Digital Preamp DAC Review

The NAD C 510 proved itself to be an excellent DAC through its entire residency in my stereo system. From its understated looks, to the plethora of connections (including HDMI with video pass through), and its custom decoding engine, the C 510 is more than capable to handle all your digital conversion needs.

Combine that with a built in volume control and a separate remote control and the NAD looks to be vying for a spot as the central digital hub of your whole system. I found the NAD’s sonic signature to be subjectively flawless to my ears. All I can say is that over the month that I had the NAD in my system, I really came to enjoy the way that it sounded. When I switched it out for either of the other DACs I had around, I simply felt that my music was missing something. To me, it neither embellished nor diminished any of the audible spectra. It simply gave me exactly what was there, all of it. And it did it in a manner that made me want to turn up the volume and get lost in the music.

At an asking price of about $1300.00, the NAD looks to be an excellent value in the current DAC market. It’s also somewhat unique in that I am only aware of maybe two other audio-only DACs that have HDMI connectivity. The only possible criticism I could come up with is its inability to decode a native DSD bit stream over HDMI or USB. With native DSD playback being the “it” thing at the moment, its absence on the NAD may turn some users away Note, however, that many high resolution music albums are available both in PCM format as well as DSD. So, if you purchase the NAD C510, get your music downloads in the PCM format.

Although the converted and down-sampled DSD files I played through it sounded good enough that, in reality, it may not make much of a difference. If that isn’t a deal breaker for you, then by all means audition the NAD C 510. I think you will find its pristine sound quality very addictive. I highly recommend it!

The author wishes to acknowledge the assistance of Senior Editors, Dr. David Rich and Robert Kozel, in the preparation of this review.