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NAD C658 Streaming DAC Review

MKW

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As it is, I would be very curious to A/B the M12 and the C658 to see if there is any audible difference.

As it so happens, I have the M12, C388, Node2i, and between the time I started reading this thread and getting to this page 13/14 of the thread, ordered and received the C658, swapped the HDM-2 MDC card from the M12 into the C658 - and sat for a quick listen (last night). I'm also familiar with miniDSP (a discussion in this thread), and have/used; DDRC-88A/BM, 4x10HD, nanoDIGI 2x8, and 2x4HD - these have been used as crossovers for LXmini speakers and a stereo pair of open-baffle Phoenix (alternate) subs - all Linkwitz designed DIY speakers.

First impressions of the SQ difference between M12 and C658 (without Dirac so far) - M12 wins on natural 'fluid' presentation and stereo separation - I suspect that's due to the AKM DACs, think M12 has separate DAC for each channel (with each 2ch DAC being used in mono to smooth results), lower noise rating, vastly-configurable stereo sub and line outs, and overall better build and other components including case and isolation. Also goes without saying, M12 has a larger, touch-enabled screen, and the menu system is thorough (many more configuration possibilities), and is a genuin pleasure to use.

The C658 has a newer firmware update system (all happens through BluOS update), which is much easier than the old USB-stick system of M12 and C388 generations. Another benefit of C658 is the 5GHz wifi (better connection). Then there is Dirac, which the M12 doesn't have - despite my requesting a Dirac MDC card from NAD on several occasions (as if they care what I want). I find the C658 menu system ready to use, very limited (compared to M12) and overall extremely under-utilized by NAD dev team (pales in comparison even to the previous generation C388 - which does make use of the screen color capability).

In the used market, C658 is selling around $1k, and M12 around $2.5k. Depending on what a person is looking for, both are great units, and both could be so much better with more development time accomplished through firmware updates. So much potential with these products if NAD would allocate more resources to it (especially with the M12). I suspect the C658 is already performing very near its hardware limits (SQ-wise) and suspect the M12 firmware is leaving a lot on the table (which is sad).
 

MKW

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guess that I'm not worried about the touch screen

It's not just the touchscreen capability of the M12... M12 has a many more configurations available in its menu system; each input has its own gain level setting + variable or fixed, line-level outputs and sub outputs (4 unbalanced outs + main unbalanced and balanced have their own gain setting + high-pass/low-pass + cutoff frequency of each, also the screen is bigger and does a much better job of using that screen real estate to full-effect and even though it doesn't display album art, the track name/album/artist is displayed so big, you can see it from listening position easily (in my situation) - this is not true of the C658 or C388.
What I'm saying is, the M12 isn't just a touchscreen version of the others, it is much better in many ways - so much so, it's not even in the same class.

Look at the volume display on the C658... why did they make it so small? Why not use the full screen size - like it was developed as a remedial Summer-school coding class project. The M12 screens appear to have been designed by a professional.
 

JDRCapeCod

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Can anyone comment regarding the quality of the included calibration microphone? I see that there is a mic calibration file that can be downloaded from the NAD site, but it is not unique to each mic. I am curious if using something like a Dayton UMM-6 or a MiniDSP UMIK-1 would deliver a noticeably better result, especially if you have paid for Dirac full-bandwidth. Curious if any owners have experimented with this.
 

Dathzo

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Can anyone comment regarding the quality of the included calibration microphone? I see that there is a mic calibration file that can be downloaded from the NAD site, but it is not unique to each mic. I am curious if using something like a Dayton UMM-6 or a MiniDSP UMIK-1 would deliver a noticeably better result, especially if you have paid for Dirac full-bandwidth. Curious if any owners have experimented with this.
I have used both umik-1 and the default mic for Dirac. I like the umik-1 results better and it actually measures better (using REW and rhe umik-1). The difference is mainly at high frequencies, so you would need the full Dirac in order to note anything. Other users have suggested there is no difference, but I my case, I found one
 

Dathzo

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Was doing today some quick calculations based on what Amir has measured, see below:

1630671897329-png.3171940



Note that at 4V output, the theoretical SINAD would be -65db. Amir measured -90db at 4V (I understand that corresponding to -4.5db volume attenuation). Extrapolating measured values, and assuming linearity, the unit would have an excellent SINAD at around -20db of volume attenuation (-111db).

This is of course extrapolating values and assuming linearity that may or may not be there but just wanted to share the numbers with you guys.
 

JDRCapeCod

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I have used both umik-1 and the default mic for Dirac. I like the umik-1 results better and it actually measures better (using REW and rhe umik-1). The difference is mainly at high frequencies, so you would need the full Dirac in order to note anything. Other users have suggested there is no difference, but I my case, I found one
I purchased the umik-1 and will be completing a new calibration. Without Dirac I can hear that I have some phase issues at certain frequencies. I am hoping for a good result (changed furniture in the room and then heard the issue). Reading through the Dirac manual I see that they recommend pointing the mic towards the ceiling and using the 90 degree file...also that the mic gain should be at 100%. I am hoping that Dirac (I have the full frequency version) addresses what I am hearing.
 

Dathzo

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I purchased the umik-1 and will be completing a new calibration. Without Dirac I can hear that I have some phase issues at certain frequencies. I am hoping for a good result (changed furniture in the room and then heard the issue). Reading through the Dirac manual I see that they recommend pointing the mic towards the ceiling and using the 90 degree file...also that the mic gain should be at 100%. I am hoping that Dirac (I have the full frequency version) addresses what I am hearing.
Good luck, Dirac does wonders in many setups. Make sure to be patient and carefully do the measurements. The correction will be as good as the data you input to it
 

MKW

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unit would have an excellent SINAD at around -20db of volume attenuation (-111db).
Maybe that's why the unit sounds fine to me - haven't and wouldn't need to adjust the volume level that high.
Thanks for sharing that information!
 

samysound

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Have there been any updates from NAD with regards to enabling Dirac Bass Control capability? I can find anything on the NAD website so I assume the answer is no?
 

MKW

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Have there been any updates from NAD with regards to enabling Dirac Bass Control capability? I can find anything on the NAD website so I assume the answer is no?
Maybe there is an answer here: https://nadelectronics.com/dirac-live/
I find that DiracLive immediately acknowledges the C658 and allows calibration - even without Dirac login (no registration required), same as miniDSP DDRC-88A/BM.
In the case of miniDSP, there was a one-time $99 hardware-linked purchase to add bass management (license stays with the unit by firmware).
In the case of NAD, seems the included LE-version is bass-only (16Hz - 500Hz), and you can pay $99 to extend it to full-frequency (20Hz - 20kHz), which also buys multiple PC license and allows more usefulness as the entire freq. range is calibrated together as a cohesive system (think bass to sub crossover smoothing, and full-range gain/phase/impulse alignment).
 
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Have there been any updates from NAD with regards to enabling Dirac Bass Control capability? I can find anything on the NAD website so I assume the answer is no?

An NAD Facebook group member just shared an interesting response they received from NAD support regarding Dirac Live bass control. This one seems to be more informative (and encouraging?) than the usual canned responses.

------------
Vishnu M. (NAD Electronics)
Oct 11, 2021, 10:36 PM EDT

Hello #####,

Thank you for contacting NAD Electronics.

We do apologize for the undue delay regarding bass management with DIRAC, we are currently working with DIRAC to implement their Bass Management module into our products. They are an excellent partner and are mutually excited about our implementation.

Unfortunately, our schedule was affected greatly due to emergency measures put in place by The Government of Canada and Province of Ontario to stop the spread of COVID-19. This resulted in our staff being migrated to a work-from-home model as we were no longer able to access some of our test facilities at our corporate headquarters just outside of Toronto. Though our development team was able to continue working on the software and firmware, our quality assurance team was no longer able to effectively test their results.

Through an easing of Emergency Measures along with some creative ways our QA Teams have been able to test in their home offices, we are slowly getting back on track. We hope to provide an updated timeline and get the much anticipated Dirac Bass Management system out to the C658, M33, M10 and other NAD 2 channel Dirac capable products as quickly as possible.

For more about firmware updates, new products or other great news, please Follow Us on Facebook at https://www.facebook.com/nadelectronics, Like us on Twitter @NADElectronics or sign up to our e-mail News Letter at www.nadelectronics.com, scroll to the bottom and click the Newsletter link.

Thanks for your patience, understanding.

Regards,
Vishnu M
NAD Support Crew Analyst

------------
 

TonyB

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What I'd love to hear is that they're releasing a new model as an updated version of the C658, to iron out its inherent defects. They updated the M10 pretty quickly, but the C658 remains current. Great concept for a device, but poorly implemented.
 

bluefuzz

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What I'd love to hear is that they're releasing a new model as an updated version of the C658, to iron out its inherent defects.
What inherent defects? Aside from the less than stellar SINAD (which is of course still beyond audibility) and curious lack of USB input, I can't think of anything I would change. Smaller box perhaps ...?
 

RVCollura

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What inherent defects? Aside from the less than stellar SINAD (which is of course still beyond audibility) and curious lack of USB input, I can't think of anything I would change. Smaller box perhaps ...?
I use the USB input on mine all the time.
 

RVCollura

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The USB is only for connecting a harddisk or the measurement microphone. It's not an input to the dac.
I don't understand, I have high res music files on a thumb drive that the C658 plays. How could they be playing if not through the DAC?
 

bluefuzz

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I have high res music files on a thumb drive that the C658 plays. How could they be playing if not through the DAC?
Yes of course your files are playing through the DAC, but that's because your disk or thumbdrive is mounted on the filesystem of the C658. That's not the same as what we normally understand as a 'USB DAC' interface. The point is that the USB won't accept asynchronous input from the USB output of a Raspberry Pi for example or another type of computer.
 

RVCollura

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Yes of course your files are playing through the DAC, but that's because your disk or thumbdrive is mounted on the filesystem of the C658. That's not the same as what we normally understand as a 'USB DAC' interface. The point is that the USB won't accept asynchronous input from the USB output of a Raspberry Pi for example or another type of computer.
OK, got it. I use a JDS DAC on a different system that way.
 

TonyB

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Could a C658 user please confirm how the output level settings work? I've read the manual but it's not clear (at least to me!). This is what it says:

"Fixed: Output level is fixed and the C 658’s Volume Control is bypassed. This feature is sometimes referred to as “Cinema Bypass” because it allows the C 658 to be used for the front channels of a surround sound system by relegating the volume control function to the surround processor"

It then goes on to talk about individual inputs. Is it the case that each input channel can be set to have a fixed or variable output? That seems to be what it's saying.

The reason for asking is that I need a variable preamp output for my active speakers, and the possibility of adding an external headphone amp to upgrade headphone listening (I've read that the headphone output of the 658 is mediocre). As there's no digital output I would need a fixed level analogue signal for a headphone amp.

Ideally I would set the XLR outputs to 'fixed' to feed a balanced headphone amp, and the RCA outputs to variable to work as a preamp for the active speakers.
 

DogsDieInHotCars

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Taking a look at this review, Armir couldn't get coax/optical to lock. Do we have a decent idea of the SINAD of the digital inputs?
 
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