NAD C658 Streaming DAC Review

[pogo]

Are you sure DL on C658 runs at 192khz?

You can't say that for sure, but my M33 does.

 

[pogo]

Interested in which addon module? How do you PEQ headphones on C658?

NAD DSD USB MDC
PEQ: Link

 

[Sparkles]

NAD DSD USB MDC
PEQ: Link

Learning. Thanks. BluOs also converts DSD from library.

 

[Dexter_prog]

Thanks for all the replies. I'm actually now between a used c 658 or a fairly priced new minidsp shd studio. I'm leaning towards the later as it comes with the full license, and I can use the dac of my primare i35 prisma. The only thing holding me down is if this dirac thing is worth the 1000 euros this little piece of hardware costs. It's the only thing I can do for room correction as I can't treat the room as I am renting and don't want to mess with the walls.

 

[Joris881]

I'd like to get some input on a little problem I have.
My C658 is connected to my tv trough an HDMI Arc MDC card.
When watching tv (multiple sources, cable tv, netflix, youtube, ...) if the tv signal jumps from one segment to the next it seems like the NAD cuts out for a split second.So for instance when watching a commercial on cable tv it cuts out when every new commercial clip starts.
When watching and interview on youtube it cuts out every time one person stops talking and another one starts.
It takes around 1-1,5 seconds before the audio start again so you miss the first couple of words every time someone new starts talking.

Has anyone noticed the same behavior?

 

[Parts]

Has this C658 been tested again with another sample since this post was created, what is the general concensius of it's performance today?

On paper it still looks reasonable and like a budget version of the Master series, with Dirac and so forth.

 

[NADKEF listener]

I owned one icm with an M23 and it worked perfectly fine for me, great device! Switched to the M33, mainly for the display. My very subjective feeling is that the M33 is more accurate. Seeing all the price reductions and offers, i think that the C658 is about to be updated/replaced. My advice would be to score a used one for $700-$800. Often the warranty is 5 yrs, so what could go wrong..

 

[evanfsmith]

This is a review and detailed measurements of the NAD C658 streamer and DAC. It also acts as a preamplifier with Phono and line in. A cool feature is inclusion of Dirac Room EQ and balanced out and you get a killer feature set. For that, you need to pay though to the tune of US $1,650. The owner purchased a factory refurbished which I see going for US $1,300.

The overall design looks quite nice with a larger and informative display:

View attachment 54653​

Here is the back panel:

View attachment 54654

The only feature missing that should be there is the unit acting as a USB DAC. It has a USB connector but that is it acting as a host, playing content from external storage.

Since there is no USB input, I started my testing with Coax S/PDIF. To my surprise, the frequency counter on Audio Precision was jumping all over the place as was the waveform. This indicate lack of lock on the incoming clock which could either be a design flaw or something broken in this unit.

I then switched to Toslink optical with the same result. Wanting to make sure my analyzer had not failed, I powered another DAC and it worked perfectly there.

Without these inputs working, the only digital path I had was streaming using Roon which worked fine. Roon complains that it is not certified but worked anyway.

Streaming DAC Audio Measurements
Here is our usual dashboard:

View attachment 54655

Even though performance bests the specification at 0.005% distortion, this is well below acceptable in a high priced device like this:

View attachment 54656

The only other test I can run this way is jitter:
View attachment 54657

That spray of spikes should not be there. Fortunately it is at -130 dB so not an audible concern.

Conclusions
Shame to see quality control or design issues in a brand like NAD. Even if the digital inputs were not broken, the performance of the DAC fails to even match a half decent $9 phone dongle. So despite great feature set, NAD needs to go back to the drawing board and clean up its implementation.

Needless to say I can't recommend the NAD C658.

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As always, questions, comments, recommendations, etc. are welcome.

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I am a new member, although I have referenced this website many times over the years. Thanks for the excellent reviews and discussions. I own a NAD C-368 so naturally I was concerned with the poor performance mentioned in this review. When I initially got the NAD, I did notice jitter. However, with subsequent BlueOS updates, the jitter started to subside significantly. Also, I have noticed that the 368 performs much better when warm. To provide a new update to this review, I have used Multitone Analyzer to check the performance of my own preamp. It is not as detailed as the original review, but it does show that another testing is warranted. It is still far from the best DACs, but at least it has acceptable performance now. Here is what my testing showed at 16 bit jitter. Please note this testing was done with DIRAC and Analog Bypass off.

Measurement​	Right Channel (JTest 16)​	Left Channel (JTest 16)​
Fundamental Level	1.3 dBFS @ 11,025 Hz	2.0 dBFS @ 11,025 Hz
Overall Level (RMS)	-3 dB	-2.8 dB
Total Noise	-61.9 dB - -65.5 dBA	-62.4 dB - -66 dBA
SNR	63.2 dB	64.4 dB
SFDR	84.1 dB @ 99.7 Hz	82.9 dB @ 20.1 Hz
Effective Number of Bits (ENOB)	10.6 bits	10.8 bits
Delay	0 ms	0 ms
Drift	8.6 ppm	6.3 ppm
Jitter (Peak)	2073.1 ps @ 99.6 Hz	2960.1 ps @ 29.6 Hz
Jitter (RMS)	164.3 ps	145.2 ps

 

[SIY]

When I initially got the NAD, I did notice jitter.

How so?

 

[NADKEF listener]

What does a measurement of a C368 say about the C658?

 

[evanfsmith]

How so?

The preamp began making ticking noises over the audio for up to 10 minutes after being turned on. However, the ticking eventually subsided once the amp was warmed up. I initially assumed that this was related to jitter. This morning, I conducted additional measurements using the Multitone Analyzer.

In my findings for both the left and right channels, I noticed that the results are cleaner when testing each channel separately. However, this might not be as indicative of overall performance since we typically listen in stereo.

 

[evanfsmith]

What does a measurement of a C368 say about the C658?

Since I posted new results today (see attached graphic). I will provide the explanation for that test result.

Performance Analysis

• Signal Consistency: Both channels exhibit stable fundamental frequency outputs, which is positive for overall audio performance.

• Distortion Levels: Both channels show similar distortion levels with higherTHD, which may affect audio fidelity.

• SNR Variability: The left channel's positive SNR is beneficial, while the right channel's negative SNR indicates clarity challenges due to background noise.

• Jitter Management: Very good

• Good Dynamic Range: The SFDR values indicate that both channels can effectively differentiate between the desired audio signal and noise, which is important for high-quality audio playback. The right channel exhibits a slightly better SFDR at 28.4 dB, which indicates a capacity for handling dynamic audio content effectively.

Overall Performance Rating: Moderate to Good

• Left Channel: The channel performs well with a strong signal and a stable output but has moderate levels of THD.

• Right Channel: Although it shows a slightly lower fundamental output and a negative SNR, its good SFDR suggests that it remains capable of differentiating between desired audio signal and noise while also handling dynamic material.