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NAD C658 Streaming DAC Review

T.J. Turner

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Please find below an ansnwer from Nad support

"Hello Jan,

Thank you for contacting the NAD Electronics Support Center. I sincerely apologize for the delay in getting back to you as we have experienced a higher volume of requests due to COVID-19 isolation.

With regards to the ESS DAC in the C658, it has the ES9028 ESS DAC.

We hope this helps! If you have any further questions or concerns, please feel free to get in touch.

Best Regards,

Bob Moran
NAD Support Specialist"

Yeah that's the details in their documentation. But why did Hans only find Burr Brown DACs in his.
 

JanZak

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Yeah that's the details in their documentation. But why did Hans only find Burr Brown DACs in his.
I found something like this in the Polish review of the magazine "AT.TEST"
"The audio track is based mostly on popular N5532 operational amplifiers, which can be found both in the input circuits and also behind the main c / a converter –ES9028Q2M. The word "main" was not accidentally here, because there is one more DAC - PCM5121. Judging by the location, it can be concluded that it supports subwoofer output."
 

LuvTheMusic

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@T J Turner: Check the NAD white paper for the 658. The Burr-Brown chips are not DACs. One of them is an "Asynchronous Sample Rate Converter to buffer the incoming digital source signals to reduce jitter"; the other is an ADC to convert analog sources to digital if DIRAC is used or if the output is to be streamed across a Bluesound connection.

I saw Hans' review and noted the photo of the innards of the unit -- perhaps the ESS DAC is hiding under that upper circuit boar, but that's purely a guess!

By the way, the white paper also is somewhat hidden -- look in the Downloads section on the product page.

Enjoy!
 

T.J. Turner

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The c658 just got a major update. Has anyone noticed any differences?

BluOS 3.10.0. Released August 18, 2020.
• Support for TIDAL My Mix.
• Updated kernel libraries.
• New grouping synchronization.
• More robust WiFi drivers.
• Updated audio libraries.
• DAC tuning.
• Improvements for network stability and power management.
 
Last edited:

LuvTheMusic

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Just installed the update, but did not notice any differences. Then again, I don't use TIDAL, don't have groups, and had great WiFi already. Curious as to what the "updated audio libraries" are and what was done with "DAC tuning", though.
 

T.J. Turner

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Just installed the update, but did not notice any differences. Then again, I don't use TIDAL, don't have groups, and had great WiFi already. Curious as to what the "updated audio libraries" are and what was done with "DAC tuning", though.

Well the kernel and audio libraries and DAC tuning is primarily what I was looking at. I wondered if they would produce different test results.
 

JDRCapeCod

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Well the kernel and audio libraries and DAC tuning is primarily what I was looking at. I wondered if they would produce different test results.
I did the update last night. I really did not have any complaints about the unit before the update. I have not had time to do any listening but will post when I do. Thanks for the heads up on the update!
 

JanZak

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If you had problems with freezing the system and crackling in the speakers, nothing has changed, unfortunately. I only got the impression that the whole thing was louder, but I'm not sure.
 

Brian6751

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FYI - This update was for all BlueOS devices and is not specific to the C658
 

EB1000

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The level was recalibrated. The overall volume was increased by 3db. Other than that, only Bluos related updates (MCY version was changed from 1.44 to 1.45)
 

JanZak

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After the last update, it only gets worse. C658 freezes every day as I start listening and I have to reset it.
 

LuvTheMusic

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After the last update, it only gets worse. C658 freezes every day as I start listening and I have to reset it.

Same as T.JTurner: no freezes here, and no one else seems to be reporting that issue. Possibly defective unit? One idea, just because it's software and we all have heard "when all else fails, restart": if you don't mind starting over, you could do a full factory reset. See page 4 of the manual for instructions. And powering all the way down, ideally unplugging the AC power for a few seconds, might help?

Powering down will not affect settings. A full reset will lose all the settings, presumably including WiFi credentials, any control settings (e.g., balance / tone controls), renaming of inputs, etc.

Again, just a guess at a possible fix.
 

JDRCapeCod

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I have been doing some listening after the update...nothing immediately jumps out at me as improved or different. I really was scared to purchase this unit based on the problems that people have been experiencing but I have had not issues at all from day one and really like it. I am starting to think that some units out there are just defective and should be replaced. It's not an inexpensive piece of gear and should perform as advertised!
 

T.J. Turner

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I have been doing some listening after the update...nothing immediately jumps out at me as improved or different. I really was scared to purchase this unit based on the problems that people have been experiencing but I have had not issues at all from day one and really like it. I am starting to think that some units out there are just defective and should be replaced. It's not an inexpensive piece of gear and should perform as advertised!

All the early reviews are based on earlier firmware builds. And most of the negative comments are from people who read those reviews and quickly formed opinions.
I got mine as open box around Jan 2019
The firmware was 3.2 something and I had technical issues the moment I tried to play the first song! And as I tried to unravel that issue I found more issues. But by firmware 3.8 the major issues have been fixed. There are still some minor annoyances such as the headphone output sharing the same volume and dirac processing as the main output. But I've learned to just live with them as they haven't really gotten in my way.
As of now its a fine device I'd still recommend with its current firmware.
However if I was going to replace this unit I'd go for the NAD M33.
 

JDRCapeCod

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All the early reviews are based on earlier firmware builds. And most of the negative comments are from people who read those reviews and quickly formed opinions.
I got mine as open box around Jan 2019
The firmware was 3.2 something and I had technical issues the moment I tried to play the first song! And as I tried to unravel that issue I found more issues. But by firmware 3.8 the major issues have been fixed. There are still some minor annoyances such as the headphone output sharing the same volume and dirac processing as the main output. But I've learned to just live with them as they haven't really gotten in my way.
As of now its a fine device I'd still recommend with its current firmware.
However if I was going to replace this unit I'd go for the NAD M33.
I do notice that I need to shut of Dirac when I plug in my headphones, not a major issue but more of an oversight in my opinion. I just looked at the M33 and it looks sweet, but it is missing something that I would love to have, which is a record output (either analog or digital). There is no way to get the output of the built in BluOS Node to feed anything else. I have a control system in my house with distributed audio and control. If I just had a way to get the output of the Node to the input of my distributed audio system (at a fixed level), it would be perfect. Currently I need to add a second Node for that functionality. Another thing that I don't understand about the C658 is that is has a full color display, but they don't take advantage of it. The only time you see anything in color is when it turns on! Maybe we will see an update in the future. I am using mine with a March Audio amp and love it.
 

Puddingbuks

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I do notice that I need to shut of Dirac when I plug in my headphones, not a major issue but more of an oversight in my opinion. I just looked at the M33 and it looks sweet, but it is missing something that I would love to have, which is a record output (either analog or digital). There is no way to get the output of the built in BluOS Node to feed anything else. I have a control system in my house with distributed audio and control. If I just had a way to get the output of the Node to the input of my distributed audio system (at a fixed level), it would be perfect. Currently I need to add a second Node for that functionality. Another thing that I don't understand about the C658 is that is has a full color display, but they don't take advantage of it. The only time you see anything in color is when it turns on! Maybe we will see an update in the future. I am using mine with a March Audio amp and love it.
The Darko review on the m33 point at the two way bluetooth, where you can also send audio from the m33 to another device.
 

audioholics68

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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:


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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I have just bought this unit NAD C658. I am absolutely clueless to your reviews. I have just finished setting the unit up. Got it acting as a Pre-amp to my Rogue Audio Magnum Atlas Power Amp. Turntable - Technics SL-1500 with the Ortofon Blue stylus, Yamaha CD-S2000 and speakers are KEF LS50.
The set-up process was a breeze with DIRAC LIVE and BluOS on my iPad Air.
The sound from the turntable, CD player and in-house server to my ears are clear sharp with good bass. I don't have any fancy words like most of these audio magazine reviewers.
My point here is, you can use all kinds of spectro testing equipments to test all these audio equipments. The bottom-line that matters is our individual ears on how we perceive the sound.
I LOVE the unit and I highly recommend to anyone who is looking for a pre-amp with streaming capability and a built-in DAC. I am also very pleased with the price point.
 
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