CHORD ELECTRONICS DAVE

[Jawed]

Actually one project I've always wanted to tackle is to create an illustration of going from 44.1 to 705.6 with each of the filters published for various DACs (though I don't know whether SABRE publishes their filter specs!) vs various lengths of sinc.... Alas, I no longer have access to MATLAB, etc. to whip this up easily. Maybe someone else can carry the torch!

I believe GnuOctave is popular:

https://www.gnu.org/software/octave/

Ear Level is a very informative site for digital audio:

http://www.earlevel.com/main/2010/12/05/building-a-windowed-sinc-filter/

Archimago has some nice stuff:

https://archimago.blogspot.co.uk/2018/01/audiophile-myth-260-detestable-digital.html
http://archimago.blogspot.co.uk/2018/02/musingsmeasurements-on-blurring-and-why.html

Now playing: Fenne Lily - Three Oh Nine

 

[Jawed]

A Blu2/Dave costs £17k. Is it too much to expect that the correct interface between them should be specified?

I tend to agree.

Rob's testing regime doesn't seem to be tough enough, which means digital connections introduce sound quality problems in others' system (but not his). Though there is a strong consensus that his galvanic isolation on USB is about the best found on any DAC.

I think Rob has been climbing a much tougher learning curve than we can really appreciate. Most of us know how tiring and frustrating audio evaluations can be. Well that's Rob's 9 to 5... at least some days. And the performance levels are entirely new in the industry. For example DAVE will show RF problems much more clearly than Mojo because it's more transparent.

Ideally, as Chord releases new digital components, they really are immune to the digital connection. But there are plenty of reports of people whose systems still show problems even when there's an optical input to DAVE alone. But if there's another mains-powered component in the system, then the problem is caused by an interaction of DAVE and that other component. Or two other components and not DAVE. And people will blame DAVE. So Chord can't win. (Not to mention there are people who have a strong dislike for the low distortion sound of the optical connection!)

Single powered-component systems, such as Devialet, do offer a great solution to all this digital cable nonsense. Wi-fi source!

I can imagine Chord producing a system-in-a-box like Devialet, eventually. Apart from anything else, they're really easy to sell!

Back in the 90s, my Audio Synthesis transport and DAC was sold with an option to buy from them their preferred optical cable to connect them and it worked really nicely. That whole lot was sold to me directly, not via a retailer.

Also Rob appears to think the improvement with ferrites on the BNC cables for BluDAVE is quite minor. Others think it's a big deal. I think there's a strong consensus that the sound of CD replay isn't much affected by ferrites on the BNC cables, though. The implication being that USB streaming is the real cause of, apparently, quite strong disagreement on the sound quality variations caused by connecting Blu2 to DAVE with BNC cables.

Now playing: Big Thief - Masterpiece

 

[Jawed]

Not correct, Rob’s explained before:

“issue we have here is signal correlated RF noise from the actual BNC data corrupting Dave's ground plane, not Blu side noise getting through.”

https://www.head-fi.org/threads/cho...-official-thread.831343/page-87#post-13696701

Rob later talked about how Blu 2's FPGA is a source of noise itself:

https://www.head-fi.org/threads/chord-electronics-dave.766517/page-627#post-13882837

Now with digital electronics we have something called ground bounce. This is current from switching activity within the FPGA or chip that goes into ground, and this current causes the ground wires (and ground plane as a ground plane has inductance too) to bounce up and down due to the ground inductance. We have two forms of noise - clock noise, which for the M scaler is 208 MHz; and noise due to logic level transitions as the internal data signal propagates through the FPGA gates. These delays are from 100pS to 500pS, so are in the 1 to 5GHz region - centred around 2 GHz. This noise (unlike clock noise) is signal correlated, and this would explain why use of 2GHz ferrites improves depth perception. Also, the galvanic isolation is effective at 208 MHz, but is ten times less effective at 2 GHz.

Now playing: Siv Jakobsen - Dark

 

[flyte3333]

Rob later talked about how Blu 2's FPGA is a source of noise itself:

https://www.head-fi.org/threads/chord-electronics-dave.766517/page-627#post-13882837



Now playing: Siv Jakobsen - Dark

Yes indeed, especially regarding Blu2 galvanically isolated BNC outputs: “the galvanic isolation is effective at 208 MHz, but is ten times less effective at 2 GHz.”

 

[flyte3333]

Back in the 90s, my Audio Synthesis transport and DAC was sold with an option to buy from them their preferred optical cable to connect them and it worked really nicely. That whole lot was sold to me directly, not via a retailer.

Playback Designs have been doing this for a long while and still do (high speed fiber cable between transport and DAC)

 

[rayl]

I believe GnuOctave is popular:

https://www.gnu.org/software/octave/

Ear Level is a very informative site for digital audio:

http://www.earlevel.com/main/2010/12/05/building-a-windowed-sinc-filter/

Archimago has some nice stuff:

https://archimago.blogspot.co.uk/2018/01/audiophile-myth-260-detestable-digital.html
http://archimago.blogspot.co.uk/2018/02/musingsmeasurements-on-blurring-and-why.html

Now playing: Fenne Lily - Three Oh Nine

@Jawed, thanks for the pointer to Octave!!! My MATLAB is super rusty after a few decades, but... it works... except if you do too much calculation, the PC grinds forever w/o a way to stop Octave other than killing it....

@jrfmd, I generated 4 plots below which I hope will help. They show:

1. a sine wave with the sampled data points... the sine wave is plotted at horizontal resolution of 64x the sampling rate
2. upsampling/interpolation using the ideal sinc (which is infinite) to 8x the sampling rate
3. upsampling to 8x using a zero-order hold (i.e. repeating the sample value 8 times)
4. upsampling to 8x using a simple connect-the-dots method (i.e. straight line betw data samples)

The plots are pulled from the middle of a 10 second period.... that's bec the edges are not bandwidth limited (values fall suddenly to zero) so the middle minimizes aliasing artifacts.

Imagine that filling in between the upsampled dots is now left to later processing (possibly all analog). The point is, there's much less to fill in with the upsampled data than with the original data -- but that isn't super useful unless the upsampled data gets you closer to the original waveform.

I am lacking the time to discover what filters are used by real upsampling DAC chips like SABRE, etc.,to show those... but in case anyone wants to tweak, the MATLAB code (which runs in free Octave) is at: https://pastebin.com/YxDycsCB

I've also picked small #s to speed calculation and plotting -- and extreme examples for illustration purposes. (If you are curious, you can intentionally introduce aliasing and see what it looks like!)

This illustration has been on my mind ever since getting a Blu2 and having friends ask "why would you buy an upsampler???" I've had a hard time sketching on paper by hand, but now I have pseudo-real (except for the over-simplified filters apart from sinc) illustrations thanks to Octave.

 

[jlbrach]

I own the dave/blu2 combo and have experimented with and without ferrites and to be honest if nobody ever mentioned the subject i would have been just fine.....

 

[Triode User]

I think there's a strong consensus that the sound of CD replay isn't much affected by ferrites on the BNC cables, though. The implication being that USB streaming is the real cause of, apparently, quite strong disagreement on the sound quality variations caused by connecting Blu2 to DAVE with BNC cables.

I have never seen that suggested. On the contrary and as discussed Rob says the source of the RF is the MScaler circuit and this gets into the dual bnc. My personal listening tends to confirm that the faux brightness and detail associated with RF is there just the same whether from CD playback on the Blu2 or whether streamed to Blu2 via usb.

 

[flyte3333]

I have never seen that suggested. On the contrary and as discussed Rob says the source of the RF is the MScaler circuit and this gets into the dual bnc. My personal listening tends to confirm that the faux brightness and detail associated with RF is there just the same whether from CD playback on the Blu2 or whether streamed to Blu2 via usb.

This seems consistent with John Swenson's theory about leakage current loops between SMPS's. And these high impedance leakage currents sailing right through digital isolators and transformers.

https://www.computeraudiophile.com/...grounding/?page=9&tab=comments#comment-735311

and

https://www.computeraudiophile.com/...rounding/?page=10&tab=comments#comment-735903

and

https://www.computeraudiophile.com/...rounding/?page=37&tab=comments#comment-799484

 

[flyte3333]

Speaking of leakage loops.

Well I've setup my battery powered microRendu and battery powered optical ethernet converters for the weekend. Proper battery powered, no coupling to mains power at all. So the microRendu inputs are perfectly isolated from mains power. Therefore Dave's USB input is perfectly isolated from mains power (ground / leakage loops). And that's using the impedance matched and properly shielded Uptone USPCB connector for the best USB signal integrity to feed into Dave's USB input.

I was comparing this to my Uptone LPS-1 powered microRendu and John Swenson recommended switch with grounding trick to block most leakage currents from 'sailing right through the transformers'... which is probably about as good as it gets for anything coupled to mains power. It's purpose is to approximate a battery but with very low output impedance. But it still has some coupling to mains power.

The difference between the above two microRendu setups is very noticeable. The battery powered microRendu is noticeably less fatiguing after >1 hour listening, than the LPS-1 powered microRendu - smooth and without listening fatigue much like the battery powered iPhone Roon endpoint I tested a page or two earlier in this thread. Again, there's that desire to want to crank the volume with the battery powered microRendu. The music flows, feet tapping, no fatigue after an hour of listening. Just like earlier observations.

What is NOT easily noticeable (I can't differentiate at all to be perfectly honest) - any difference with TOSlink !!! And the battery powered microRendu (v1.4 with Crystek clock upgrade for those of you playing at home) would be about as good as it get in terms of ultra low noise output and USB signal integrity feeding Dave etc etc...

I was actively listening for the differences Rob has mentioned that battery powered USB source edges optical in terms of flow and focus... I couldn't hear it ! I really wanted to hear those differences too to give me an excuse to keep the microRendu !!

I posted the same observations on the Hugo2 thread previously but I thought Daves transparency might reveal some differences between the highest quality USB source and Toslink...

Amazing.

What has it re-enforced to me?

1. Dave is incredible on all inputs (you all knew that already). I only heard these differences (especially the listening fatigue and desire to up or drop the volume) reveal themselves over extended listening, while enjoying the music - not by quick and stressful A/B'ing.

2. Rob's DPLL is the real deal (as if I didn't know from Mojo and then Hugo2 already)

3. Leakage currents (and their effects and associated RF effects) getting into the Dave are bad. I think Rob has used the term fungus somewhere before. Somebody needs to make a digital isolator that doesn't let any leakage currents through - none, nada, like optical isolation. Easier said than done of course otherwise I'd do it myself and be a very rich man selling it to everyone.

4. Dave is incredible. The leap from Hugo2 is everything I wanted it to be.

Chain is just Dave driving headphones directly.

 

[jrfmd]

The whole universe is a 'black box', which we all go through life desperately kidding each other, and ourselves, we have a chance of understanding. LOL

I'll drink to that
jeff

 

[jayz]

That would be to admit there’s an issue, and Chord wouldn’t do that.

I don't believe these sort of issues are clear cut as one would like. Just to give another example, a decade or so ago we started to see the very first EVs (Electric Vehicles) on the road. As you can imagine, these cars did not have combustion engines to drown out road and wind generated noise so people started noticing road noise. Manufacturers were aware of this and so they included extra noise dampening but if you know the principles behind acoustic noise isolation, there is always a compromise because if we engineer panels and body sections of cars to such an extent that it blocks all noticeable noise, it will end up weighing as much as a heavily armoured bullet proof car.

Getting back to Dave, I presume what is happening here is that with astonishingly low distortion and noise specs, suddenly external factors considered insignificant with other lesser dacs, have now become prominent and noticeable. One could argue then that it is the manufacturers responsibility to deal with some of this (and I am sure Chord Dave will have better noise immunity compared to others) but inevitably the designer has to stop somewhere commercially viable for a particular iteration of the design.

Just take it easy, tell your friends that your DAC is so good that even quantum noise can be heard, and even better - try to see if you can tackle it in your system. Who knows maybe your solution might even have commercial potential i.e. you can sell to other owners.

 

[Emerald Core]

Question to @Rob Watts and Dave owners who own streamers with dedicated internal clocks.

I have ordered Dave along with an Aurender N10.

The main point is, should I connect them with USB or AES (with oxco clock from N10)?

Is the internal clock inside the Dave superior to OXCO inside N10? Has anyone compared Dave sound with or without using external clocked signal from a streamer ?

This will help me decide investing on the cable while waiting for delivery of both.

Thanks

 

[Crgreen]

Obviously, I meant metaphorically, in the sense of the great unknown.

So what you are saying is that there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know.

Which actually, is true

 

[Crgreen]

What has been said several times by Rob is that the performance of Blu2 is extraordinary even without ferrites and that any discussion of ferrites is mere fine tuning and is not fundamental or essential.

I prefer to use my own ears, and anyway, Rob’s aren’t available.