Secrets of Home Theater and High Fidelity - Best of Awards 2020
NAD Electronics continues to charge ahead in the digital high-resolution domain, recently developing two key components; the NAD Masters Series M10 BluOS integrated DAC/amplifier and the C 658 sans amplifier.

NAD C 658 BluOS Streaming DAC Review

For those unfamiliar with BluOS network streaming, (or perhaps you live under the preverbal audio rock), the proprietary, multi-room operating system developed under the Lenbrook brand, has been included in the new models.

Further, and perhaps just as exciting is the integration of the DIRAC Live Room Correction software. In for review is the NAD C 658 which comes with a license for DIRAC Live with an option to purchase an advanced, full frequency spectrum version.

NAD C 658 BluOS Streaming DAC

The C 658 Streaming DAC can be used as a stand-alone preamplifier in your system with both digital and analog inputs, (including a MM phono input), or in your system as purely a DAC/streamer. And if that weren’t enough, NAD incorporated their MDC, Modular Design Construction, by providing empty hardware slots that allow for future hardware upgrades, like an HDMI 4k switcher.


NAD C 658 BluOS Streaming DAC

  • DIRAC Live Room Correction with microphone
  • BluOS Operating System
  • High-Resolution playback
  • Stand-alone preamplifier with DAC
  • Modular future options
  • Network support and Streaming
  • Balanced preamp outputs
  • MM phono input
  • USB connection

NAD C 658 BluOS Streaming DAC Remote


I don’t care which side of the digital debate you’re on, but everyone should have a digital streamer in their Hi-Fi system. For me up until now, it was a USB-tethered laptop to my preamplifier. As much as that works for playing digital files stored on my laptop or network, it isn’t conducive for streaming services. 


(20Hz-20kHz) <0.005% at 2V out

Frequency Response:

±0.3dB (20Hz – 20kHz)

Tone Controls
DAC Chipset:


DAC supports:


High-Resolution formats:

MQA, FLAC, WAV, AIFF, converted DSD via BluOS app

BluOS app
Native Sampling Rate:

up to 24bit/192kHz

BluOS Operating System
Bluetooth, Qualcomm aptX HD wireless
Internet Radio
Balanced Preamp and subwoofer Outputs

17 1/8” wide X 3 15/16” high X 16” deep


22.3 lbs






nad, dac, streaming, hi res, bluos, DACs Reviews 2020

I loved the NAD Masters Series M50.2 Digital Music Server I’d reviewed 2 years ago, and I hated letting it leave my system. It was pretty much perfect for me.

NAD earlier this year released two products that piqued my interest. Although the “table-top” Masters Series M10 integrated amplifier and BluOS streamer is an excellent choice as a source product, I was a bit more intrigued by the NAD C 658 music streamer. But please read Michael Galvin’s assessment of the M10 here.

Certainly, more affordable than the Masters Series, the C 658 offers high-resolution playback wrapped in a preamplifier/DAC component that would work with my Hi-Fi system with outboard amplifiers.


Like most NAD components, other than the Masters Series, the grayish-black metal C 658 is relatively conservative in appearance. The face sports a centrally located LCD display screen that gives most of the information you need to operate the C 658: input selector, volume level, etc. To the left is a ¼” headphone jack and the screen navigation button along with the on/off switch. With the standby mode and remote control, you may rarely use the on/off button. The other side has the volume control, keeping in mind it’s only active when using the C 658 as a preamplifier otherwise it’s set at fixed.

The rear is much more involving having both digital and analog inputs: Two optical and coaxial inputs, two sets of RCA line-level inputs, and a grounded, phono input. A USB input allows playing music from digital files stored on the disk and is where the microphone is plugged in. NAD provides balanced or unbalanced pre-outs and dual subwoofer outputs. A 12v trigger in/out along with IR in/out allows integrating the C 658.

NAD C 658 BluOS Streaming DAC Back

NAD also provides two MDC, (Modular Design Construction) slots for future hardware upgrades, an HDMI module is currently available. And finally, the C 658 has two antenna connections, one each for Wi-Fi and Bluetooth.

The NAD C 658 is nominally 17” wide for rack mounting and is almost 4” high. The magic, of course, is all on the inside of this modestly priced, overachieving component.

The ESS Sabre 32bit DAC decodes most codec audio files including the controversial MQA, (another discussion) along with FLAC, WAV and a plethora of formats.

Two-way Bluetooth capability with aptX HD which supports 48kHz/24-bit LPCM audio, either stream to the C 658 from your device or transmit from the C 658 to a set of wireless, Bluetooth enabled headphones.

BluOS is the proprietary operating system NAD incorporates in the C 658. Not only does it allow control from an app-driven mobile device, phone or tablet but also desktop or laptop computers. BluOS essentially organizes and controls the music you play whether via a music service like Tidal or Spotify, (and many more) or just simply internet radio, along with digital files stored on the network. BluOS also works to control a multi-room system with any Bluesound products.

Remote Control

The NAD C 658 comes equipped with an excellent and full-featured remote control. It’s used more however if the C 658 is set up as a preamplifier. However, the remote has full input selection, volume and tone controls.

NAD C 658 BluOS Streaming DAC Remote Control

Dirac Live

Many moons ago (2013), I was invited to an early demonstration of the Dirac Live software meant for room correction. Dirac was developed at Uppsala University in Sweden.

Read the short piece I wrote about the goals of the Dirac Live software, but the point is Lenbrook has it incorporated it into the C 658 in both a “light” version with the option to upgrade to the full version for $99US.

The software can be applied with an app on your mobile device, or from your desktop. I’m inclined to believe most will use the mobile version. I actually tried both. After answering a few basic questions about the listening situation; two-channel, a chair or sofa or even auditorium, the software is ready to take some measurements.

The C 658 comes with a pre-calibrated microphone that connects on the rear of the unit via USB and the software asks to take measurements predominately around the prime listening location. The software sends both frequency and impulse responses through the speakers and develops a filter structure that can be stored on the BluOS app and applied at will.

The software further allows you to make your own modifications to the achieved curve by raising or lowering points on the curve, to as many dB’s as you’d like at any frequency. Want a bit more bass at a frequency of 200 Hz, no problem. Add a point and drag it. I must tell you, as much fun as this can be, it will probably get you in more trouble playing around with the settings. I know I spent an inordinate amount of time trying to get the results I wanted. Either way, the Dirac software does let you save as many filter profiles as you’d like, however you can load up to five into the C 658 for use.

I ended up storing three filters I was happy with and applied them based on what I was listening to; orchestra, vocal-centric, etc. The general results were a bit tighter bass, fuller space around vocals and a bit more zest around instruments like trumpets. Although each filter gave me the slightest more clarity, I frankly couldn’t achieve anything better than just leaving Dirac off. Perhaps months from now I will find the perfect solution, I’m glad the C 658 included Dirac Live, the solution to my room is there.

Looking at Figure 8, the Dirac app on my phone shows room correction from 80Hz-500Hz.
Figure 8, Dirac app on phone


I did spend some significant time with the C 658 as a preamplifier, meaning I used it connected to a pair of NAD C 268 amplifiers used in mono mode.

NAD C 658 BluOS Streaming DAC Front

I’d been sent a pair of the PSB Alpha P5 for fun and I had a PSB SubSeries 125 on hand using one of the C 658 sub outputs. This made for an excellent “little” system.

NAD C 658 BluOS Streaming DAC volume control

Digressing from the review of the NAD C 658 for a bit, I wanted to give some kudos to the Alpha P5 stand-mounted monitors. These are little gems and literally, any music lover or audiophile should have a pair. Paul Barton is such a smart man when it comes to speakers, and the P5 is a smart if not a “best buy” audio product. This constitutes the fifth generation of the Alpha and is priced at $349 for the pair. It’s a small 2-way design with a 3.4” aluminum dome tweeter and 5.25” mid-range driver.

NAD C 658 BluOS Streaming DAC Speaker

Anyway, read our review of the PSB Alpha P5 by Jim Milton, I agree with him, wholeheartedly.

Once the component is unpacked, antennas screwed in and the C 658 is powered up, remember to download the BluOS app, I have it on both my phone and my tablet. The C 658 easily found my network and my tablet identified the new “player” — the app doesn’t work without a player, obviously.

As a preamplifier, I didn’t use the phono stage separately but did send my analog signal through a line level, as did my CD player. I could have sent my CD player via a digital signal using my CD player as a transport and let the C 658 DAC handle the conversion.

I have installed the C 658 serving my Parasound P6 preamplifier and Halo JC5 stereo amplifier. My latest speaker review is a pair of Marten Trio, forthcoming.

During playback, the information screen shows the track and volume level, (it will show “fixed” if using another preamplifier). It will also identify the source playing, the name of the track, artist and how far along the track has played. If the track is MQA, it will show it, otherwise, there is no indication of the track or file playing. It would be nice if it showed perhaps the bitrate however, for local files on the network or through the USB, the BluOS app gives you more information, but you need to look through the “technical info” for more the file type, bitrate and sampling frequency.

Also, it does not show album art, if that were important to you. But from about 10 ft, the LCD screen, it is just legible from my listening position.

In Use

Upfront I will say the NAD C 658 is an excellent music source component. It should be discussed both as a preamplifier and as a DAC in my system. But there is so much to the C 658 and how it can be used, that It may be one of the most feature-rich components I’ve ever reviewed, and I don’t even have the HDMI 4K switcher module installed.

The primary use for me is as a streamer, taking my Tidal, (I’m also now playing with Qobuz) and effortlessly listening through my system using the now-very-familiar BluOS app. But the list of available services compatible with the C 658 is staggering when you also include internet radio and stored music.

The sound quality of Tidal through the NAD C 658 is as good as any CD playback – believe me I’ve compared by throwing in a disk and playing the same tracks through the C 658 streamer.

Maxwell Street

Ronnie Earl “Maxwell Street”

Listening to Ronnie Earl’s electric guitar on his album Maxwell Street, specifically, the bluesy Blues for David Maxwell renders his guitar sharp and articulate. Activating the Dirac room correction further focusses the chords, deepens the tone of the strings all the while taking the edginess off the keyboard organ.

Thanks for the Dance

Leonard Cohen “Thanks for the Dance”

Leonard Cohen’s Thanks for the Dance album is full of his typical poetic and deep-voiced tracks. The C 658 exudes the lower range of his voice, he talks more than sings. Several tracks have a mandolin playing along with his voice, almost to counter the sweetness of the instrument with his rustic voice. The playback is rich and full.

I couldn’t say I heard any significant difference playing the C 658 as the primary preamplifier in lieu of feeding the signal to my Parasound P6. No change in soundstage, no reduction is music depth and power. Playing the newly released John Coltrane, 1964 recording, Blue World in MQA required me to drop the volume a few decibels. The sound from the C 658 is relaxed, yet detailed. His saxophone is nicely balanced with the piano and gentle percussions.

Oh Mercy

Bob Dylan “Oh Mercy”

Bob Dylan’s Oh Mercy album has some amazing audiophile-like tracks. The beautiful melody of Man in the Long Black Coat is rendered “to die for” through the C 658. This recording and playback create such wonderful imagery and musical cohesiveness. Instruments beautifully spaced around his centered voice.

My One And Only Thrill

Melody Gardot “My One And Only Thrill”

Finally, I’ve just started appreciating Melody Gardot with her rich but quirky voice. Listening to CD-quality versions of tracks from her My One and Only Thrill from 2009 through the NAD C 658 streamer does her voice and the instruments justice. The music is somewhat jazzy, and she finds a balance of sweetness and throatiness and hearing her breathy voice is superb.

I did limit my Bluetooth listening with the headphone aptX HD and wireless headphones, specifically the new Sennheiser Momentum. The synergy between the two is excellent, sound-wise. Other than that, most if not all my streaming was done with the Wi-Fi feature of the C 658.


Finding a streamer should be a priority for your system and making it the heart of your digital playback. I made NAD C 658 mine

  • Excellent sound quality.
  • Robust streaming capabilities.
  • MDC construction for future expansion.
  • Inclusion of DIRAC Live.
Would Like To See
  • Slightly larger display for my aging eyes.

The NAD C 658 is incomparable when you consider the features packed into this component. At this price point, there is barely a handful of stand-alone DACs let alone DAC/Streamer/Preamplifier. From a sound standpoint, perhaps the Auralic G1 at about $2,700 will give you comparable playback, again though without many of the features.

I wouldn’t hesitate to recommend the C 658 as your primary preamplifier either, making it the heart of any HiFi system.