CHORD ELECTRONICS DAVE

mavwong said:

  I will be also building my own cable for HE1000, using mundrof silver gold solid core and silver plated CU wires that plug direct at the back of Dave. Till then I will report back my finding again.

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something like this... 

  ? 

mavwong said:

Guess who's hands is this in the pics? Lolz. These hands are freezing cold as I type now as the room at parkroyal Singapore are like winter in London.

Just have a lengthy good chat with Rob the guy. Friendly guy with great wisdom and knowledge.

I not posting review yet just impression later. But I am now much poorer man than I was 2hours ago.

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beolab said:

I think it is a little strange that we don't have any real amateur / professional longer review yet?

I know it is just pre-units out and it is hard to judge whats better with the DAVE against the rivals like MSB and Total DAC , but i know some people sitting on listening impressions but they have just scraped on the surface with short comments on the difference to the Hugo that i feel a little remarkable, so my quest is to wright a little longer sound impressions review in detail from you who have listen to the DAVE .

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panurus said:

Demo the 5 and 6 december .

http://widescreenaudio.be/chord/

it will be possible to compare Mojo, Hugo TT and Dave.

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brightonjel said:

 
Very late to the party here, but just wanted to echo everyone's sentiments that having Rob participate to the breadth and depth that he does is hugely appreciated.  I had the pleasure both of meeting him and hearing Dave at the Audio High event recently (and thanks to Hiyono for cross posting my brief review of that evening at #567 in this thread).  From what I heard that evening, and even in the very challenging circumstances that prevail at those events, posters here who have "pre-bought" Dave won't be disappointed.  The ability of Dave to bring back depth to the hi-fi experience was very noticeable, and something I heard even before Rob's talk went into more detail, in particular about where the technology was different relative to his earlier work on Hugo and hence highlighted what he learned during its development.
 
I will be very interested to see the results of Rob's further investigations here. Initially, I was a bit surprised that it was improving the SN ratio through adding further high-order noise shapers that seemed to be the thing that made the most difference in this area.  
 
If you think about audio depth perception, numerous studies have shown that it's driven by the ear hearing time-delayed reflections from the original sound source interacting with the environment.  Indeed, if you sat in an anechoic chamber with one fixed and one moveable sound source, moving one source further away would just make it sound quieter, not more distant, which is not what happens in real world acoustics.  In practice, environmental reflections reach the ear both delayed and significantly attenuated, with both parameters providing clues about the acoustic in which the sounds occurred. The brain then does its own remarkable thing and creates the impression of a soundstage that we can bring to mind even with our eyes closed, one that can be intimate or expansive, studio or stadium.  But this attenuation also means that the depth cues are, therefore, akin to signal-modulated noise, heard by the ear some time after the primary signal. Therefore, I went away from Rob's talk thinking that it was his work in removing the tendency of a DAC to itself modulate the noise floor of the signal chain with the source waveform that was improving depth perception, but that doesn't seem to be the case.
 
Of course, we live on the world of engineering here and not pure theory, so it may just be that it's in the interaction of the noise shapers with the - now - signal-independent noise floor that makes the difference; pull down the quantization noise far enough and it enables other engineering parameters to become evident.  Regardless, my speculating won't answer the question but Rob's experiments can, so I hope he will keep us in the feedback-loop as he gets closer to un-picking the complex, interwoven threads in this area.
 
Looking forward too to hearing first impressions as people get to plug Dave into their own systems, as well as what comes back from professional reviewers once they get to do more of a comparative analysis than most of us can do from our own resources.
 
Exciting times indeed, and thanks again, Rob, for coming to visit and spending time chatting!  As an expat Brit it's always fun to meet visitors from the UK, especially when they come with 20+ years experience in digital audio design .

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rob watts said:

  Now when I first got to 350 dB performance (that's the best I can do with available FPGA and flip flop speed) I was simply amazed that the brain was so sensitive. How can it detect such small errors? Perhaps its down to something else, and the noise shaper number is merely a proxy for something else going on in the analogue domain. But recently (a month ago) I upgraded internal digital (no analogue consequences at all) noise shapers within Dave from 220 dB to 350 dB - and lo and behold depth did get much better. So that suggests that the brain really is sensitive to absolutely no error for small signals. But it still perplexes me that minute effects can be so easy to hear.
 

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bmichels said:

Rob,

based on some tests it seems that the HifiMan HE1000 lack some authority from the front Headphone out, but... it sound VERY good from the XLR on the back when using this adapter cable.

But... then the DAVE gets very hot. :mad:

--> Does this usage of a 35 ohms headphone connected on the XLR line out (like it is 100% OK to do with TotalDAC) may cause some damage to DAVE ?  What is the Impedence of those XLR line out ? 

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rob watts said:

  Depth perception is indeed mostly down to the reverberant signal to direct sound signal ratio. But another important cue is due to HF absorption of the air, so brighter sounding sounds are perceived as closer. Quite how the brain determines that the frequency response of signal is degraded I don't know; perhaps the brain subtracts the frequency response of  reverberant to direct to get a another depth cure, or perhaps its simply bright sounds is inferred as being closer. 
 
For sure, if the reverberant signal is attenuated or distorted with respect to the larger direct signal then depth perception suffers. Indeed, in all of my career of listening and then explaining the results of listening tests, small signal non-linearity is the only factor that I have correlated with depth perception. With noise shapers you get distortion of very small signals, in that signals below the noise shaper noise floor are lost and signals that approach the noise shaper noise floor have reduced amplitude. This is why fundamental linearity measurements are important, as they show the amplitude of small signals changing with level. Using FFT's with the result calibrated at -60.000 dB, then re run the test at -120 dB you check that the level is actually -120.000 dB (with results adjusted for noise). Using my Pulse Array DAC's you get pretty much perfect results (no consistent error). Conventional delta sigma have measurable errors, R2R DAC's have even more, as its impossible to match resistors accurately enough.
 
In the bad old days, when my designs had significant fundamental linearity errors, improving this problem did lead to better depth perception. Moreover, when I used to design cables in the 80's, one could always hear a correlation between conductor purity, metal surface oxides and depth perception. In this case, the oxides in metal to metal interfaces (crystal to crystal inside the wire and contact to contact) create small signal non linearities, with resistance being a tiny bit higher for small signals than larger signals. But although it was easy to hear depth being degraded, you could never measure this distortion.
 
Before the Dave project, my target for noise shapers was better than 200 dB distortion and noise performance. that's around 1000 times more capable than high end noise shapers. But with Dave I had ten times more gate capacity than ever before; also whilst listening to different noise shapers when developing Hugo I could hear large changes in depth perception. This indicated that my assumption that 200 dB was good enough was not correct.
 
At this stage I should indicate that there are actually two entirely different distortion mechanisms that are important to noise shaper designs (there are other things but this is the most important). These are:
 
1. Noise floor modulation. This is where the noise floor modulates with signal level - so large signals give greater noise than small signals. The brain is remarkably sensitive to this problem, and can easily hear unmeasurably small levels; it perceives it as smoothness or warmth to the sound when the problem gets smaller. With gross noise floor modulation you hear it as grain in the treble. Now all DAC's (except mine) have very large and measurable noise floor modulation, which explains why they sound harder (they normally add some 2nd harmonic to fatten up the sound to hid the innate lack of warmth). Additionally, reducing noise floor modulation improves instrument separation and focus, and you reduce the loudest instrument taking your attention problem.
 
2. Fundamental linearity - how accurately small signals are reproduced (small signal linearity). Now this only affects depth perception, it does not do anything else. And I have not come up with any change in depth that wasn't explained by small signal linearity.
 
Now a noise shaper has both problems - making a better noise shaper with say 220 dB performance than 200 dB will have lower noise floor modulation and better small signal linearity.
 
So when I designed a 220 dB noise shaper and listened to it, I could easily hear better depth - and maybe a bit smoother. So better than 200 dB is a good rule of thumb for noise floor modulation, but certainly not for depth. Indeed, over a 90 day period I constantly improved the noise shapers and came to the absolutely remarkable and frankly amazing conclusion that there was no limit to how good the noise shaper needs to be in order to resolve depth perception. I ended up with an very complex 17th order noise shaper that had 350 dB performance. 
 
With 90 days of work and getting an improvement every day in depth, I could hear now a cavernous depth perception. This is very exciting, as its long been a major problem of mine that one can hear depth so accurately in real life, but high end audio sounds flat as a pancake. Listen to a real organ and choir in a cathedral - if you are 100 feet away and shut your eyes, it sounds uncannily 100 feet away. I am now starting to get something like that depth perception with loudspeakers - but I guess the weak link now is the ADC, which is my next design challenge.
 
Now when I first got to 350 dB performance (that's the best I can do with available FPGA and flip flop speed) I was simply amazed that the brain was so sensitive. How can it detect such small errors? Perhaps its down to something else, and the noise shaper number is merely a proxy for something else going on in the analogue domain. But recently (a month ago) I upgraded internal digital (no analogue consequences at all) noise shapers within Dave from 220 dB to 350 dB - and lo and behold depth did get much better. So that suggests that the brain really is sensitive to absolutely no error for small signals. But it still perplexes me that minute effects can be so easy to hear.
 
But this brings me full circle. I have always been puzzled that cable small signal non linearity was never measurable and if its true that -350 dB performance is necessary then this proves why we can't measure cable effects - they are simply too small, and the brain is just too sensitive.
 
Funny that work in noise shapers can solve a puzzle with metal purity with wires...
 
Rob

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