NAD C658 measurements and teardown Q

[kukynas]

don't wanna derail the owners thread but... 

 

I think NAD intentionally crippling this category to not jeopardize their master series where more profit's happening, I believe they are going to release master series version of this streamer as they are refreshing entire line of master series so it would be logical

we already know they can build highly capable DAC section as the specs and measurements of the M33 are out on several sites already so it's real shame as Dave pointed out they didn't utilized same potential of the DAC inside of the C658

 

don't get me wrong, this streamer sounds great but could have sounded better (in this respect cleaner compared to other DACs I own) especially as there is no alternative on the market 

they could have raised the price a bit if they felt they couldn't produced better sounding/measuring unit for said amount and people would still buy it, and maybe even more, I'm sure I would knowing I would get 10db extra noise floor and 30db extra distortion free and clean spectrum

 

at the end of the day no matter how I look at it there's no streamer/dac/preamp/dsp all in one box on the market in this or anywhere near price category so if anyone is looking for one which does all of this in one box I think C658 is no brainer 

 

[Satanica]

11 hours ago, kukynas said:

at the end of the day no matter how I look at it there's no streamer/dac/preamp/dsp all in one box on the market in this or anywhere near price category so if anyone is looking for one which does all of this in one box I think C658 is no brainer

 

miniDSP SHD?

 

https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-minidsp-shd-dac-dsp-and-streamer.4286/

[kukynas]

I’m aware of SHD but if you ever worked with volumio you wouldn’t consider it as a streamer, in best case renderer or end point so no competion in my pov

different case if we would add node 2i into the package than you might get better combo but with 2 boxes

[gillmaverick]

Hi Daniel ,

That's a massive effort Mate. How does it sound after your upgrade and how much did it all cost If you don't mind me asking ?. I  am happy with the NAD but If can improve it further like what you have done that would be awesome. I have zero skills and knowledge though.

[kukynas]

4 hours ago, gillmaverick said:

Hi Daniel ,

That's a massive effort Mate. How does it sound after your upgrade and how much did it all cost If you don't mind me asking ?. I  am happy with the NAD but If can improve it further like what you have done that would be awesome. I have zero skills and knowledge though.

 

Hi, 

no upgrade as yet, still collecting parts, custom made regs from Korea supposed to arrive end of this or early next week so than I can start working on it but still no guarantee we'll see any improvement/benefit. I'm afraid that the volume control chip at the back of the output stage will be limiting factor for any improvements but hope is there and unless I try it we won't find out, I plan to do it in steps and measure it after each upgrade stage so we should see if and what and after all this we can calculate what's the cost of each (potential) improvement

Anyone can do it as parts are available on the web, it's mainly about soldering skills and appropriate gear (soldering and rework station) 

 

most of the parts arrived and how it will look like compared to original PSU

 

 

[sleach]

On 26/11/2020 at 1:38 AM, kukynas said:

at the end of the day no matter how I look at it there's no streamer/dac/preamp/dsp all in one box on the market in this or anywhere near price category so if anyone is looking for one which does all of this in one box I think C658 is no brainer 

 

That's how I think of it too: excited to see how your experiment goes and maybe try and replicate some of it if you have success. But....

 

13 hours ago, gillmaverick said:

If can improve it further like what you have done that would be awesome. I have zero skills and knowledge though.

That is me as well!

[kukynas]

regs arrived so started to work on PSU...

 

 

rework rig...

 

 

all mounted on the board, tested with main supply and all works as it should...tomorrow soldering traces, output connectors, cables and desoldering old buck converters

 

   

[kukynas]

it's aliveeeee!!! lol

 

[kukynas]

good news, it works...bad news it does nothing to the distortion, I spent good half day to think about it and I'm bit afraid that unless I completely eliminate those buck converters I won't be able to move on and fix that psu distortion...

 

below captured with no signal playing, basically 100hz psu distortion with its harmonics, at this point there is no reason to continue with digital part PSU tweak, so I will move onto step #2 which is power rails for analog section and will hope to get better result, if not than there is very little to do unless as said I would completely replace the power rails circuit with my own which is impossible as it's all sensed by m-processor for stand by and time out function

Another set of regs is on the way so hopefully in week or 2 I'll be able to continue...  

 

 

    

[martinhdk]

Just curious... (Please bare with my lack of technical insight)

I am considering the C 658 purely as a streamer with Room Correction. So: fixed volume/tone control and no "external" analog/digital input.

Would "bypassing" preamp and not using external inputs improve noise and distortion in any way?
Or are the issues present throughout the entire signal path?

 

(I see that you have done a test with Tone Control disabled - so I'm guessing it's a lost case)

Best regards
Martin

[kukynas]

Hi Martin,

unfortunately you can't bypass preamp section or I didn't found the way how to do it but you can set fixed volume output for each input channel including network streaming, I would stay above -2.5db on the dial as that's the point where the distortion starts to rise proportionally

 

distortion + noise (no signal) is well below -130db so shouldn't be a concern to anyone, it's slightly worse with signal playing as distortion gets into audible range, on the other hand still in low levels.

The main difference I can hear compare to my Adi RME 2 PRO is in fine details, i.e. cymbals are better articulated and more delicate but one have to be really focused to pick it up, if I never heard Adi I most probably won't notice it, NAD has on the other hand more pronounced dynamics most probably caused by higher harmonics which ads slight warmish character to it...  

 

Dan

 

[martinhdk]

1 hour ago, kukynas said:

Hi Martin,

unfortunately you can't bypass preamp section or I didn't found the way how to do it but you can set fixed volume output for each input channel including network streaming, I would stay above -2.5db on the dial as that's the point where the distortion starts to rise proportionally

 

distortion + noise (no signal) is well below -130db so shouldn't be a concern to anyone, it's slightly worse with signal playing as distortion gets into audible range, on the other hand still in low levels.

The main difference I can hear compare to my Adi RME 2 PRO is in fine details, i.e. cymbals are better articulated and more delicate but one have to be really focused to pick it up, if I never heard Adi I most probably won't notice it, NAD has on the other hand more pronounced dynamics most probably caused by higher harmonics which ads slight warmish character to it...  

 

Dan

 

Hi Dan,
Thank you for the elaboration.
Sounds like the C 658 will have more than sufficient resolution for my gear & ear.

I'm probably more likely to hear (and hopefully appreciate) the overall sonic signature than the lack of dynamic range.
 

Best regards
Martin

Edited December 7, 2020 by martinhdk

[Lars V]

@kukynas thanks for all the work. I am currently also looking at the NAD C658. However, this thread and others, plus the fact that I just sent back the NAD C298 cause it turned off by itself every time after 4 hours running, is making me cautious of NAD products. 

My current setup is Quad Z2 speakers, Musical Fidelity M5si, Bluesound Node 2i, Topping E30 DAC (temporary), REL T/7i, IFI Power Station, Silent Angel Bonn N8 and all good cables (power, ethernet, RCA). I have an XTZ Edge laying around and had it connected to the Schiit Saga+ before, which sounded nice. The M5si is a step up. I do like the all in one box idea of the C658 as I really like to combine DIRAC, Bluesound Node 2i (Tidal Hifi MQA) and the bass control and definition of the XTZ or C298 all together. Of course I can add MiniDSP Studio or SHD, but then I start to get a lot of "boxes". Such a shame that NAD just didn't get their quality level up one notch more.... I mean for the money. The fact that the C298 (which sound very neutral, detailed with great bass control) just turns off while the music is playing is just unacceptable, no matter the price. Guess I am hoping for too much (Dirac, MQA, BluOS, Purifi, etc) for the moment. I am sure in the next few months other brands will come with similar all in one boxes. One thing I forgot to mention (the reason I didn't get the NAD M10) is that I am looking for a HT IN option, cause I am connecting the power amp to the Pre amp of my HT receiver. The M10 doesn't have that option, the M5si has, and on the C298 you can switch between XLR and RCA in puts. Well, long story, and not yet a satisfying solution

[Snoopy8]

8 hours ago, Lars V said:

@kukynas thanks for all the work. I am currently also looking at the NAD C658. However, this thread and others, plus the fact that I just sent back the NAD C298 cause it turned off by itself every time after 4 hours running, is making me cautious of NAD products. 

My current setup is Quad Z2 speakers, Musical Fidelity M5si, Bluesound Node 2i, Topping E30 DAC (temporary), REL T/7i, IFI Power Station, Silent Angel Bonn N8 and all good cables (power, ethernet, RCA). I have an XTZ Edge laying around and had it connected to the Schiit Saga+ before, which sounded nice. The M5si is a step up. I do like the all in one box idea of the C658 as I really like to combine DIRAC, Bluesound Node 2i (Tidal Hifi MQA) and the bass control and definition of the XTZ or C298 all together. Of course I can add MiniDSP Studio or SHD, but then I start to get a lot of "boxes". Such a shame that NAD just didn't get their quality level up one notch more.... I mean for the money. The fact that the C298 (which sound very neutral, detailed with great bass control) just turns off while the music is playing is just unacceptable, no matter the price. Guess I am hoping for too much (Dirac, MQA, BluOS, Purifi, etc) for the moment. I am sure in the next few months other brands will come with similar all in one boxes. One thing I forgot to mention (the reason I didn't get the NAD M10) is that I am looking for a HT IN option, cause I am connecting the power amp to the Pre amp of my HT receiver. The M10 doesn't have that option, the M5si has, and on the C298 you can switch between XLR and RCA in puts. Well, long story, and not yet a satisfying solution

NAD is no different to other brands in reliability but sorry to hear about the C298.  Curious why you did not swap with another unit and try it.

 

You already know about the advantages of C658 and there is an owners thread here

The C658 does have HT bypass..  You can fix the volume of an input (page 13 of manual).

Edited December 18, 2020 by Snoopy8
Typo

[stereo coffee]

On 11/10/2020 at 8:42 AM, kukynas said:

first of all I'd like to just remind people about measurements and findings from ASR web where measurements and discussion started and based on which I made my own so I take Amirm's figures as reference point.

I came across same issues as he did in terms of inability to measure the unit under standard conditions so I had to overcome them but about that bit later 

 

before we start here are original measurements and findings from Amirm, what is more interesting is that the same findings were captured independently on 2 devices, node 2i and C658, what is even more interesting is that both devices even if in different price category exhibit similar performance and problems so I would assume (both owned by NAD) they share many similarities in terms of design of internals

node 2i is bit cleaner but with higher noise floor (most probably masking otherwise visible spikes like in C658) and C658 bit noisier but with lower noise floor and bit lower harmonics but more distorted  

 

https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-bluesound-node-2i-streamer.6631/

https://www.audiosciencereview.com/forum/index.php?threads/nad-c658-streaming-dac-review.12090/

 

 

 

 

acquisition HW and SW

- RME ADI 2 PRO FS - instrument grade ADC/DAC

- Siglent SDS2102X Plus - precision DSO with software package

- Siglent SDM3065X  - precision 6.5 digits benchtop multimeter

- Arta and RMA analyser software 

before I show you the measurements something about setup and numbers, ADI 2 was connected to my PC via USB and controlled via ASIO drivers, C658 was connected to ADI2 via coax cable and output of the DAC part connected via XLR cables to input of the ADI 2, ARTA and RMA levels were set based on multimeter to ~4V, unfortunately I wasn't able to reliably calibrate ARTA's signal generators level so the numbers (RMS/THD etc) are bit off nevertheless the spectrum and pattern should be showing correct levels

I can't use external signal generator with ARTA exclusive mode so 1khz frequency fluctuate a bit but shouldn't be an issue once the signal is settled and averaged 

I can't measure SNR/DNR with ARTA so unfortunately we have to believe NAD and their figures, fortunately they usually underestimate their figures so we could believe them, I also can't measure SINAD so we have to believe Amirm's figures

I can't adjust range of div. in Arta so first 1khz of frequency takes half of the screen

RMA was used just to demonstrate how would you normally measure such device (in this case unable to do properly due to problems with locking signal and distortion somewhere in the unit) and read the measured figures automatically generated by RMA analyser, they look terrible  

 

RMA analyser:

 

 

 

ARTA 1khz sine as is normally set, look at the pattern also shown in Amirm's first measurements 

 

 

adjusted setting to overcome the problem shown above, no averaging...

 

 

final THD+N after averaging for both channels (red and green) if you look at the pattern and compare it to Amirm's measurements they are close (in his picture numbers are bit squashed)

 

 

had to follow same setting as before so first lock the signal and than change it and let it run otherwise it wouldn't work, multitone again both channels

 

 

2 tone

 

 

 

jitter vs. ADI 2 (red c658) , ignore the even harmonics (generated by the signal in ARTA) again very close to Amirm's measurements

 

 

I wanted to see FFT from the scope unfortunately I found out that the termination at the DAC end isn't quite sufficient so will have to redo once the new cable arrive, for now just quick and dirty screenshot, nothing what's stands out with limits to 350khz

  

 

 

  

that's about it, any questions shoot....

 

next we'll have a look under the lid but before here's some white paper from NAD of what to expect https://nadelectronics.com/wp-content/uploads/2018/10/NAD-C-658-White-Paperwhite.pdf

 

some quotes from the white paper

 

we should be excited right? 

 

I know what's there already but let's wait for tomorrow 

 

 

ASR has perpetual habit of using levels much higher than any commercial CD or stream contains. Why they do this is a topic all of its own.  

 

I would suggest to measure a commercial CD - lets say Swiss band Sonar's Tranceportation CD , you should get figures as shown. You should then use the much lower figure that appears as +/- 350mv RMS ( shown in light blue ) , that is then realistic in terms of actual level - and not  artificial as ASR insists on using,   to assess your NAD . 

[stereo coffee]

On 11/10/2020 at 8:42 AM, kukynas said:

first of all I'd like to just remind people about measurements and findings from ASR web where measurements and discussion started and based on which I made my own so I take Amirm's figures as reference point.

I came across same issues as he did in terms of inability to measure the unit under standard conditions so I had to overcome them but about that bit later 

 

before we start here are original measurements and findings from Amirm, what is more interesting is that the same findings were captured independently on 2 devices, node 2i and C658, what is even more interesting is that both devices even if in different price category exhibit similar performance and problems so I would assume (both owned by NAD) they share many similarities in terms of design of internals

node 2i is bit cleaner but with higher noise floor (most probably masking otherwise visible spikes like in C658) and C658 bit noisier but with lower noise floor and bit lower harmonics but more distorted  

 

https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-bluesound-node-2i-streamer.6631/

https://www.audiosciencereview.com/forum/index.php?threads/nad-c658-streaming-dac-review.12090/

 

 

 

 

acquisition HW and SW

- RME ADI 2 PRO FS - instrument grade ADC/DAC

- Siglent SDS2102X Plus - precision DSO with software package

- Siglent SDM3065X  - precision 6.5 digits benchtop multimeter

- Arta and RMA analyser software 

before I show you the measurements something about setup and numbers, ADI 2 was connected to my PC via USB and controlled via ASIO drivers, C658 was connected to ADI2 via coax cable and output of the DAC part connected via XLR cables to input of the ADI 2, ARTA and RMA levels were set based on multimeter to ~4V, unfortunately I wasn't able to reliably calibrate ARTA's signal generators level so the numbers (RMS/THD etc) are bit off nevertheless the spectrum and pattern should be showing correct levels

I can't use external signal generator with ARTA exclusive mode so 1khz frequency fluctuate a bit but shouldn't be an issue once the signal is settled and averaged 

I can't measure SNR/DNR with ARTA so unfortunately we have to believe NAD and their figures, fortunately they usually underestimate their figures so we could believe them, I also can't measure SINAD so we have to believe Amirm's figures

I can't adjust range of div. in Arta so first 1khz of frequency takes half of the screen

RMA was used just to demonstrate how would you normally measure such device (in this case unable to do properly due to problems with locking signal and distortion somewhere in the unit) and read the measured figures automatically generated by RMA analyser, they look terrible  

 

RMA analyser:

 

 

 

ARTA 1khz sine as is normally set, look at the pattern also shown in Amirm's first measurements 

 

 

adjusted setting to overcome the problem shown above, no averaging...

 

 

final THD+N after averaging for both channels (red and green) if you look at the pattern and compare it to Amirm's measurements they are close (in his picture numbers are bit squashed)

 

 

had to follow same setting as before so first lock the signal and than change it and let it run otherwise it wouldn't work, multitone again both channels

 

 

2 tone

 

 

 

jitter vs. ADI 2 (red c658) , ignore the even harmonics (generated by the signal in ARTA) again very close to Amirm's measurements

 

 

I wanted to see FFT from the scope unfortunately I found out that the termination at the DAC end isn't quite sufficient so will have to redo once the new cable arrive, for now just quick and dirty screenshot, nothing what's stands out with limits to 350khz

  

 

 

  

that's about it, any questions shoot....

 

next we'll have a look under the lid but before here's some white paper from NAD of what to expect https://nadelectronics.com/wp-content/uploads/2018/10/NAD-C-658-White-Paperwhite.pdf

 

some quotes from the white paper

 

we should be excited right? 

 

I know what's there already but let's wait for tomorrow 

 

 

ASR has perpetual habit of using levels much higher than any commercial CD or stream contains. Why they do this is a topic all of its own.  

 

I would suggest to measure a commercial CD - lets say Swiss band Sonar's Tranceportation CD , you should get figures as shown. You should then use the much lower figure that appears as +/- 350mv RMS ( shown in light blue ) , that is then realistic in terms of actual level - and not  artificial as ASR insists on using,   to assess your NAD . 

 

You look to know the cutoff point where objective measurements can no longer properly assess what we hear. Using music, not generated sine waves, to subjectively assess can give even more insight , relative to other equipment. 

[Lars V]

12 hours ago, Snoopy8 said:

NAD is no different to other brands in reliability but sorry to hear about the C298.  Curious why you did not swap with another unit and try it.

 

You already know about the advantages of C658 and there is an owners thread here

The C658 does have HT bypass..  You can fix the volume of an input (page 13 of manual).

I sent the C298 back to be replaced, however the store first want to confirm the defect. Once I get a replacement, I can continue testing and see if I keep it and if I add the C658 to it. Reading your measurements and comments, it is sad that a company like NAD, who say they are dedicated to hifi, try to save a few bucks by using and constructing lesser quality parts .... I would easily pay 100 euros more just to get everything to work better together and get the max out of the DAC, etc.

Edited December 19, 2020 by Lars V

[kukynas]

On 18/12/2020 at 2:59 PM, Lars V said:

@kukynas thanks for all the work. I am currently also looking at the NAD C658. However, this thread and others, plus the fact that I just sent back the NAD C298 cause it turned off by itself every time after 4 hours running, is making me cautious of NAD products. 

 

haven't heard about Q issues with C658 so no reason to be worry about, all sw glitches were ironed out long time ago...

reg your C298 troubles, there is dedicated thread on ASR forum talking about the sudden turn off problem, NAD would replace your defecting units upon request so shouldn't be a problem, after fix no more issues...

 

 

14 hours ago, stereo coffee said:

ASR has perpetual habit of using levels much higher than any commercial CD or stream contains. Why they do this is a topic all of its own.  

 

I would suggest to measure a commercial CD - lets say Swiss band Sonar's Tranceportation CD , you should get figures as shown. You should then use the much lower figure that appears as +/- 350mv RMS ( shown in light blue ) , that is then realistic in terms of actual level - and not  artificial as ASR insists on using,   to assess your NAD . 

 

No idea what you mean by much higher levels than commercial CD, all analyser available on the market or their HW/SW counter parts like in my case using industry standards when measuring DUT's output which in case of DAC/preamp should be 2V unbalanced or 4V balanced to get -3db reference level, of course one can use much lower figures but that would mean comparing apples with oranges because you can't predict how high the preamp/dac output should be to drive everyone's amplifier hence the standard of 2/4V

are we usually listening with such high levels? most probably not but to keep consistency and measure proper capability of the DUT these are the figures set  

measuring commercial CD won't tell me anything as I don't have reference signal generated to compare it with, there's another thread about measurements of music playback/recording and impact of the ADC/DAC conversion but that doesn't show or prove how good or bad the DUT is...

[stereo coffee]

3 hours ago, kukynas said:

 

haven't heard about Q issues with C658 so no reason to be worry about, all sw glitches were ironed out long time ago...

reg your C298 troubles, there is dedicated thread on ASR forum talking about the sudden turn off problem, NAD would replace your defecting units upon request so shouldn't be a problem, after fix no more issues...

 

 

 

No idea what you mean by much higher levels than commercial CD, all analyser available on the market or their HW/SW counter parts like in my case using industry standards when measuring DUT's output which in case of DAC/preamp should be 2V unbalanced or 4V balanced to get -3db reference level, of course one can use much lower figures but that would mean comparing apples with oranges because you can't predict how high the preamp/dac output should be to drive everyone's amplifier hence the standard of 2/4V

are we usually listening with such high levels? most probably not but to keep consistency and measure proper capability of the DUT these are the figures set  

measuring commercial CD won't tell me anything as I don't have reference signal generated to compare it with, there's another thread about measurements of music playback/recording and impact of the ADC/DAC conversion but that doesn't show or prove how good or bad the DUT is...

 

Thanks for that, your reply contains so much to discuss.  We can reliably predict how high a commercial CD's output is, which is    +/-350mv RMS.  To do the same where you are, load up Audacity and allow it to read the level of your CD - the graduation scale in fractions of RMS, can  then can be seen in light blue. The peak level is far higher seen in dark blue, but we are only interested in the light blue area, as it gives us a basis to compare as you say apples and oranges, ....  in my reply apples are commercial CD levels, and oranges are power amplifier sensitivity levels. 

 

If we can agree that the source component contains the least distortion, and subjectively the best chance of hearing the actual commercial CD as it was recorded, ...are we on the same page so to speak ?  ....    a good power amplifier should you would expect, ( as audiophiles we should insist on )  for least distortion and hence best possible result,  similarly match its RMS sensitivity to very close to that same level, like this power amplifier below: 

 

In between, we can then use attenuation that does least possible change to the source audio, which is in electronics terms just resistance.

But if we begin using reactance, with anything other than resistance ... and worse change level away from the source component level, then say goodbye to ever hearing the source component properly. 

 

hence why you need to measure your NAD at +/- 350mv RMS 

 

We can now perhaps see the 2v/4v levels are those of the potential output the player has, but are NEVER representative of  the RMS level commercial CD's contain.... we should therefore always reject measurements using such figures,  that are totally unrealistic, and instead always use measurements that bear relationship to the source components we use daily.   We then have a level playing field , and not like this that ASR keeps on misleading with.

 

  

 

 

 

[kukynas]

14 hours ago, stereo coffee said:

 

Thanks for that, your reply contains so much to discuss.  We can reliably predict how high a commercial CD's output is, which is    +/-350mv RMS.  To do the same where you are, load up Audacity and allow it to read the level of your CD - the graduation scale in fractions of RMS, can  then can be seen in light blue. The peak level is far higher seen in dark blue, but we are only interested in the light blue area, as it gives us a basis to compare as you say apples and oranges, ....  in my reply apples are commercial CD levels, and oranges are power amplifier sensitivity levels. 

 

If we can agree that the source component contains the least distortion, and subjectively the best chance of hearing the actual commercial CD as it was recorded, ...are we on the same page so to speak ?  ....    a good power amplifier should you would expect, ( as audiophiles we should insist on )  for least distortion and hence best possible result,  similarly match its RMS sensitivity to very close to that same level, like this power amplifier below: 

 

In between, we can then use attenuation that does least possible change to the source audio, which is in electronics terms just resistance.

But if we begin using reactance, with anything other than resistance ... and worse change level away from the source component level, then say goodbye to ever hearing the source component properly. 

 

hence why you need to measure your NAD at +/- 350mv RMS 

 

We can now perhaps see the 2v/4v levels are those of the potential output the player has, but are NEVER representative of  the RMS level commercial CD's contain.... we should therefore always reject measurements using such figures,  that are totally unrealistic, and instead always use measurements that bear relationship to the source components we use daily.   We then have a level playing field , and not like this that ASR keeps on misleading with.

 

 

maybe we misunderstood each other but 2V/4V output level has nothing to do with music DNR scale in volts and ASR doesn't misleading anyone, as said it's industry standard, even manufactures showing their specs accordingly (below in red box) so if I'm evaluating potential improvement of my DAC/preamp I have to use reference level which in this case is 2V/4V to be able to compare figures before and after

 

 

 

 

maybe @MLXXX can shed some light on audacity as I'm not expert with it but again I think we are talking apples and oranges here, there's dedicated thread about DAC evaluation using music file via ADC/DAC process and it's impact so maybe it'll be more suitable to continue there

[stereo coffee]

1 hour ago, kukynas said:

 

maybe we misunderstood each other but 2V/4V output level has nothing to do with music DNR scale in volts and ASR doesn't misleading anyone, as said it's industry standard, even manufactures showing their specs accordingly (below in red box) so if I'm evaluating potential improvement of my DAC/preamp I have to use reference level which in this case is 2V/4V to be able to compare figures before and after

 

 

 

 

maybe @MLXXX can shed some light on audacity as I'm not expert with it but again I think we are talking apples and oranges here, there's dedicated thread about DAC evaluation using music file via ADC/DAC process and it's impact so maybe it'll be more suitable to continue there

ASR is misleading everyone with its measurements because the figures of RMS level they measure with is,  5.71 x higher than any commercial CD contains.  2v / 0.350v =5.71

 

Can you now see that the RMS level leaving any given CD player device IS always limited to the level of the CD itself ie  is +/- 350mv , and is NEVER   2v or 4v, which explains why it makes sense to always measure accurately, with actual conditions, rather than with levels that will never be achieved.

 

If we taking another example, tested cars at 5.71x their maximum speed by perhaps dropping them from space into a designated target zone, and attributed their ability at say if the average car does 180kmh max, at then 1087 kmh, we would be laughed at, and rightly so.   

 

[MLXXX]

On 20/12/2020 at 9:36 PM, stereo coffee said:

ASR is misleading everyone with its measurements because the figures of RMS level they measure with is,  5.71 x higher than any commercial CD contains.  2v / 0.350v =5.71

 

I am mystified by your line of argument.

 

You appear to be suggesting that audiophile electronic devices should be tested based on some sort of averaged out amplitude over time.  The closest approach to that I can think of a is a music power rating for a power amplifier. More generally, such an approach would be quite arbitrary, as there is no agreed figure as to what "averaged out" RMS level recordings of music contain.  Pop music tends to use a narrower dynamic range than classical music.  However some movements in a piece of classical music might be loud almost throughout; or conversely soft almost throughout.  Some organ music will contain sustained low frequency waveforms close to sine waves and with very high RMS levels.

 

In terms of using the editor Audacity, the ratio between the parts of the waveform coloured a lighter shade of blue (the RMS values) and the peaks (coloured a darker shade of blue) will of course vary depending on the particular recording.  

 

Longstanding standard practice is to measure  audiophile devices at full nominal RMS output (or input) at 1kHz . The fact that a mastered recording of music would never consist of a sustained 1kHz sinewave is beside the point. The device needs to be capable of passing at least a few cycles  at the full nominal output level without excessive distortion. This capability is needed to handle transients. It is no good if a device clips when called upon to deliver the full nominal output level.

 

Have I misinterpreted your line of argument, @stereo coffee? 

[stereo coffee]

6 hours ago, MLXXX said:

 

I am mystified by your line of argument.

 

You appear to be suggesting that audiophile electronic devices should be tested based on some sort of averaged out amplitude over time.  The closest approach to that I can think of a is a music power rating for a power amplifier. More generally, such an approach would be quite arbitrary, as there is no agreed figure as to what "averaged out" RMS level recordings of music contain.  Pop music tends to use a narrower dynamic range than classical music.  However some movements in a piece of classical music might be loud almost throughout; or conversely soft almost throughout.  Some organ music will contain sustained low frequency waveforms close to sine waves and with very high RMS levels.

 

In terms of using the editor Audacity, the ratio between the parts of the waveform coloured a lighter shade of blue (the RMS values) and the peaks (coloured a darker shade of blue) will of course vary depending on the particular recording.  

 

Longstanding standard practice is to measure  audiophile devices at full nominal RMS output (or input) at 1kHz . The fact that a mastered recording of music would never consist of a sustained 1kHz sinewave is beside the point. The device needs to be capable of passing at least a few cycles  at the full nominal output level without excessive distortion. This capability is needed to handle transients. It is no good if a device clips when called upon to deliver the full nominal output level.

 

Have I misinterpreted your line of argument, @stereo coffee? 

No not tested, rather manufactured and tested, to levels of sensitivity that match lets say within 10% of the actual RMS voltage levels available in media.  This does not  encourage ignorance of peaks in music. Quite the opposite audiophile equipment should accommodate highest peaks, and have bandwidth well beyond the Nyquist determinations.    

 

Quite a few manufacturers do this already and have been doing so since 1967 - Quad the UK manufacturer being a great example, their typical sensitivity being 500mv input for full output, which matches today's media sources. 

 

The majority of amplifiers sold today, and yesterday are voltage amplifiers - nothing more nothing less, they simply respond to the input voltage that is needed for delivering power in a 8 ohm resistance at a certain frequency usually 1khz ,  hence if used with media that does not match their sensitivity, the opportunity of available power delivery is very much lessened.  And if used with equipment increasing the source voltage level then  has reactance added in varying degrees.

 

 

 

 

 

 

 

 

 

 

 

[kukynas]

a new day (or maybe 3 months) has come and we have some progress...

 

finally was able to obtain decent signal generator to be able to measure streaming performance (instead of coax as with all previous tests) so below some figures, overall measurements of streaming module reveal lower low noise distortion and jitter side bands, on the other hand slightly higher harmonics, I can't perform entire set of measurements but this should give us enough clue of what to expect, just a note, all my measurements are undithered for those interested

In general, streaming files over network should provide better result than using C658 as coax fed DAC

in the meantime I performed stage 2 upgrade of the analog PSU rails but haven't seen significant improvements, something is still limiting factor but I expect to see some improvements after facelift of the I/V and buffer stage, fingers x

 

 

with dithered signal, higher noise floor lower harmonics

 

 

noise floor of the unit no signal playing

 

[Puresound]

Hi Dan,

I have found your very interesting project and I'm also owner of a C658 and have been doing some of the same thought of modifiying the PSU, OPA, clock.

Now I have some questions to your detailed teardown of the C658.

- Why do they have so 12 pin connector between the SMPS and mainboard? It seems like there is only 14V DC and ground!

- The XP Power SMPS (looks like ECM model) that you have chosen are very compact but looking at the R&N then it is 1% pk2pk which is normal for SMPS or have I missed something about those SMPSs?

- Do you have a picture where you connected your 5V DCs when having removed varius buck converters?

- It seems like there many NE5532 OPA (I counted 11) why so many? Have you replaced them all with OPA1612?

- Are there any low quality caps in the output signal path?

- I was thinking of removing the crystal and install a reference clock instead. What is your opnion abou that?