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NAD C658 Streaming DAC Review

amirm

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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:

NAD C658 streaming preamplifier DAC Audio Review.jpg

Here is the back panel:

NAD C658 streaming preamplifier DAC Back Panel Connectors Inputs Audio Review.jpg


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:

NAD C658 streaming preamplifier DAC Audio Measurements.png


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

Best streaming DAC review 2020.png


The only other test I can run this way is jitter:
NAD C658 streaming preamplifier DAC Jitter Audio Measurements.png


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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sashi2

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oh, that's unfortunate (though I admit I don't understand everything in your review). I was suspicious of too many sources of refurbished NAD units popping up in a Google search thinking it could be an indication of quality issues with too many of them. I've read another review that said the unit didn't start performing well until room correction was applied to it. Do you think it's possible they don't calibrate them much relying on calibration by the room correction software? Even if this is the case, it sounds like a weird decision still.
If I understand you right, no digital inputs work, that the #1 issue. Secondly, Sinad readings are sub par, especially considering the unit's list price. Do you think the poor Sinad readings are also indication of the defective unit?
 
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amirm

amirm

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No, the problem I found has nothing to do with Dirac. I should note that I had it update itself and made no difference.

The SINAD is actually slightly better than what they specify so that is not an indication of a broken unit.
 

gvl

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If not for performance, at least the feature set is decent and can acquit it?
 

sashi2

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I've bought it mainly because of the features - it promised to do exactly what i need right now - dac, preamp, dirac room correction, and Blueos to work with my other bluesound units and Tidal with MQA streaming.
 

Dj7675

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I was very close to purchasing this unit several times. After seeing the disappointing bench test results of the NAD T758 V3 I sent in, I just couldn’t trust NAD without seeing it measured first. It has a great feature list, a shame it doestn’t measure better, but not surprising unfortunately. However it does have a ton of functionality which could be quite useful in the right setup. Really strange the digital inputs wouldn’t work. Thanks to Amir for the measurements and to the owner that sent it in.
 

Veri

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No 32-tonetest signal jitter measurement?
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
 

TabCam

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Thanks, should have made that conclusion myself but did not have my morning coffee yet and a flu is not helping either :facepalm:
 

Mnyb

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It still missing a feature , very close to be the kind of product i want .

DAC/Preamp with room correction + EQ and subwofer output , why no sub out ?

Sorry it actually has sub out :) this makes things interesting . Sorry for being blind and seeing the picture correctly .

Sinad is mediocre but it has sub out and room correction thus it will sound better than any and all DAC's without sub out and room correction .

So how bad should the SINAD be before the advantage of room correction and subwoofers is overun :D 80 - dB 70- dB 60 -dB probably when noise gets iritating at listening position ?
 

MZKM

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This too was at one point on my short list of "all in one streamers", but alas maybe the NAD Master M33 will do better for $5,000?
https://nadelectronics.com/nad-mast...purifis-ultra-quiet-amplification-technology/
View attachment 54659
https://www.stereophile.com/content...tdigital-da-integrated-amplifier-measurements

Besides what’s happening >10kHz it’s pretty good.
However, 8ohm wattage and 4ohm wattage are identical, meaning you will get 3dB less power when your speaker dips to 4ohm. You will need to use the room correction to fix this.
 

Hephaestus

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Thanks for the review.

I have this unit in our living room setup and it is plagued by horrendous software. Subwoofer outputs have level issues, plopping sounds when changing tracks, some sort of occasional phantom noise...
Networking issues...
See lengthy complaint thread in AVS forum....

Stay away from this unit - headless panther tells it all.
 
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