[romaz]

  But the really fascinating thing I found with Dave is just how sensitive the brain is to small signal accuracy, in terms of how accurate small signals need to be to give convincing depth. By needing at least 350 dB noise shapers, this gives a number to the accuracy that is needed - and in short you can say the small signal linearity has to be completely perfect, otherwise depth gets degraded. And no analogue component can ever be perfect in small signal terms as any oxides will make the resistance slightly bigger for small signals. But we can make digital components perfect - at least as good as 350 dB - so the answer is to keep as much as possible in the digital domain. Hence why with Dave, no pre-amp sounds better than an extra pre-amp - and why the power amp project is so interesting, because it promises to eliminate the sound of a power amp too.
 
Rob

Rob, was 350 dB of performance some arbitrary ceiling that you reached but could not go beyond because of the limitations of current technology or was it some strategic target or threshold where you knew that by reaching it, you would gain perfect small signal linearity?  As you think about what could be improved with some future version of DAVE, what would it be?  Certainly, people will argue for having more gain available for more difficult to drive headphones but aside from that, is there any benefit in shooting for even better performing noise shapers beyond 350dB or increasing the number of TAPS or is the performance of the DAVE already so good that the limitation is not the DAC but the digital file or the transducer (headphone or speaker)?  I realize that the next big revolution could possibly occur with Davina but do you feel the DAVE is as good as it needs to be?

 

[m0nster]

Rob, was 350 dB of performance some arbitrary ceiling that you reached but could not go beyond because of the limitations of current technology or was it some strategic target or threshold where you knew that by reaching it, you would gain perfect small signal linearity?  As you think about what could be improved with some future version of DAVE, what would it be?  Certainly, people will argue for having more gain available for more difficult to drive headphones but aside from that, is there any benefit in shooting for even better performing noise shapers beyond 350dB or increasing the number of TAPS or is the performance of the DAVE already so good that the limitation is not the DAC but the digital file or the transducer (headphone or speaker)?  I realize that the next big revolution could possibly occur with Davina but do you feel the DAVE is as good as it needs to be?

Wasn't it said somewhere that about a million taps would be close enough to the required infinity of taps to perfectly recreate the signal?

 

[romaz]

Wasn't it said somewhere that about a million taps would be close enough to the required infinity of taps to perfectly recreate the signal?

Hmmm.  So is a million taps possible if the DAVE was housed in a larger chassis?

 

[GoSUV]

Rob,
 
The 20W mono amp idea does sound very intriguing to me, as where in my neck of the woods, space is at a premium and if it is only as large as the Hugo, I'd be very interested and will hold off on my search for some power amps in the near future. Does the amp work with analog line inputs or will it only work with the digital output from DAVE? Thanks in advance.

 

[romaz]

 
I guess you're right.I may have been a bit harsh in my purely speculative criticism in that post.
But  I was arguing from the perspective of music lovers  and consumers with limited funds like myself.  Like I said during the audition with the HE1000, I did I experienced no  drive problems at all.
But it seemed from Rob's response that he  was very  irritated by other things I have posted too.
To bad if so, I post what I post because I truly care about ultimate SQ as I hear it compared to live acoustic music, and for  no other reasons.
I don't intend to misinterpret or twist things as he accused me of. Nor do I intend to offend anyone for the sake of offending. I am not nasty by nature. I am seeking answers to questions I have,and that are important to me, obviously too bluntly,nothing else.
Hugo has been my beloved travel companion for 2 years now. But I have had and still  have recurring RF  problems with it and  I have also  mentioned those problems maybe too often?
 
 
The combo HE1000 and DAVE sounded sublime on most material except badly close and multimic'd recordings like Sony's recent The Marriage of Figaro which was an example where hi res in this case 24/192 played back via a very transparent chain can actually sound worse than the same played back at lower resolution and a more forgiving system.But with DAVE and to a similar but  maybe not quite the same degree with Hugo, there is nowhere for bad multimiking to hide.
I am also very interested to know  why he  seems to  prefer 16/44.1 over higher bit  and sampling rates  But it seems he won't respond to any such questions from me.
My knowledge of digital theory is very limited .But I am always willing and interested to learn new facts.To me it sounds like  a  much better option to try to capture as much as possible of  the original not bandwidth limited  analogue signal both in the frequency and temporal domains, in the first place by recording in high res instead of trying to repair  and fill in the missing gaps in time afterwards and then upsample to 32/348 or 32/768?
To the best of my knowledge that is how basically every classical music company on the market think too..
I can clearly  hear that transparency/resolution via my Hugo is  on a higher level than for example my conventional chip off the shelf Benchmark DAC2HGC  DAC.
And the main reason seems to be in the number of taps.But why  recreate only a  bandwidth limited signal ? Why not the full Monty?
Questions questions....

There's nothing wrong with criticizing a product but it becomes personal when you go after the creator of that product.  To suggest, as you have, that Rob has been either careless or incompetent in his development and testing of the DAVE can really only be interpreted one way.  This is, after all, a forum of gentleman and a certain level of respect is expected.  Look at any other DAC forum on head-fi or elsewhere and you are not likely to find one where the DAC's creator is as invested and gracious as Rob has been.  I think we each tune in everyday for Rob's pearls of wisdom. 
 
As for representing music lovers and consumers with limited funds, think about what you are saying.  What if you spent years designing and building your perfect house and you've poured your sweat and your soul into the project and then you decide to sell it for what you consider is fair market value.  Then some propsective buyer comes along and demands that you include the furniture and your personal automobile in the deal because he has limited funds.  First, the fact that he has limited funds is the customer's problem and not the seller's.  Second, he should be in no position to demand anything.  If he doesn't like the price, he should go elsewhere and see if he can find something just as good for less.  Considering the DAVE competes with DACs 10x its price, good luck finding something just as good for less.
 
Lastly, as you acknowledge that your understanding of digital theory is limited, you should be that much more careful with your demands and accept that some of Rob's design choices were perhaps made for good reason.  And as far as I am aware, Rob is not against hi-res, at least not against native hi-res PCM.  He just believes DSD as a format is flawed and not as good as PCM and he has explained very well his reasons for this.  Regardless of his beliefs, and as you have experienced for yourself, the DAVE is capable of superb DSD playback up to DSD512 through DoP.  As you wonder what other statements you might have made that could be interpreted the wrong way, just review your response to him when he indicated Davina would be capable of 16, 24 and 32 bit recordings and sampling rates from 44 to 768 kHz.  You seemed upset that Davina will capable of Redbook even though he indicated it would be capable of much more, up to 32/768.  Most people have no problems knowing that their USB 3.0 cable is capable of USB 1.0 transfers even if they never use it.  It's called backward compatibility.  I agree with you that classical music, perhaps more than any other genre, benefits from high sampling and dynamic range but there are other genres that don't and maybe never will and so Redbook is all that they aspire to. Would you buy an ACDC SACD?  Even diehard ACDC fans probably wouldn't.

 

[Kamil21]

Review Alert!

Chord Dave review in Polish:

http://www.highfidelity.pl/@main-2689&lang=

 

[analogmusic]

there are quite a few disrespectful posts here and I cringe when I read them
 
We are lucky that Rob Watts is here to answer our questions. He is a very talented digital engineer and there is noone in the world quite like him. So please be respectful in your tone when asking questions 
 
Let us not make him regret to be on this forum and let's all keep it civilized and mature.

 

[JaZZ]

  The power amp prototype has been stuck on my desk waiting for me to test it for a year now. So my priorities this year is the amp and Davina.
 
Combining Dave with the amp using the digital outputs, I am eagerly anticipating, as I expect a huge increase in transparency - in short, it will eliminate the sound of a power amp, you will be left with the equivalence of just the sound of Dave driving loudspeakers directly.
 
Rob

 
Rob, could you imagine to design a comparable amp (a variant, so to speak) for driving electrostatic headphones? I would buy one (if affordable).

 

[m0nster]

Hmmm.  So is a million taps possible if the DAVE was housed in a larger chassis?

I am hoping that Rob will chime in whenever he finds the time. I don't know what has have to change that 1 million taps would be possible. And I have no idea what other things could be upgraded in the future on DAVE, it's an interesting question though!

 

[Rob Watts]

Great news!

I dont know what to say, but all of a sudden, the DAVE does not feel so stressed any more on high listening levels like vol. 0 to -5 , it was just certain albums / Tracks i discovered with a lot of loudness and low Dynamic Range that causing this phenomena.

So im sorry if i miss led all of you, but the Dave can in fact drive the Abyss very well.

I played som tricky high bass / Dynamic classical tracks at vol -1 and i just sat and waith for the clipping, tick-tack, tick-tack,
but nothing happened! No clipping.

Try the following tracks on your DAVEś or other Amps and see if they can handle it on higher volumes without any clipping:

1. Ultra high Dynamic Range:
TIDAL - Grieg: Peer Gynt, Op.23 - Incidental Music - No.8. In the hall of the Mountain King http://tidal.com/track/4542112

2. Great vocal and sledgehammer bass song:
Josefine Cronholm : Shadow
http://tidal.com/track/2614487

3. minimal techno track that can make a PA speaker break into peaces

"Beat Beat Bad (Marco Asoleda Remix)" of Dolby D, Mickael Davis TIDAL: http://tidal.com/track/5309966

The DAVE did a very nice jobb in fact, and vol -1 is pretty darn high vol.

Nevertheless the thinness in the voices / instruments are still apparent, so the Headtrip stays as the king of the amp-throne in my house.


And a message to @Christer :
If you don't understand what im writhing, i can translate it to you in any languish you want: Swedish to Swahili its no problem

The rest of the pack seems to understand perfectly what im writhing

The impedance of the Abyss is 46 ohms, so you would need to get to +5dB before Dave starts to clip. That would relate to only 150 mA at 6.8 v, so no where near the 0.5A current limit.
 
Rob

 

[Christer]

@Christer I find this post by Rob Watts a pretty interesting take on the problems with DSD, though I certainly did not nearly fully understand it:
http://www.head-fi.org/t/702787/chord-hugo/2475

Thanks for the link, although I was actually aware of these things. I  have both been to  DXD sessions with 2L in Norway and had similar discussions with Morten Lindberg who basically says  the same as Rob I believe, ie  that  DSD can sound very good but PCM is even  better.
The more I hear well recorded DXD the more I tend to agree.
And as Rob Watts says DSD 64 for SACD was a compromise to fit things on disc.
But from the DSD 128 I have heard it seems to add a bit more air and realism than DSD 64.
Although DSD when balanced at sessions in the analogue domain as Jared Sacks has been doing for some years can sound very impressive too, in spite of its theoretical limitations.
Channel Classics recent Mahler 9 is for example among Stereophile's latest list of R2D4.
But so is one of my absolute favorites recordings  of all time, Sheffield Labs direct cut LP of Prokofiev's mighty
 Romeo and Juliet.Some SACDs where things have been stacked in edit and DSD noise trickles down into the  audible range have even less resolution than rbcd in the  highest treble range.
But in most cases DSD 64 sounds clearly  better than rbcd, but not better than DXD  or even recent well made 24/96,imho.
Some hardcore DSD believers say that DSD 256 or even 512 is the best.
I haven't heard those natively yet so I have no opinion .
But I remember asking Morten why he did not use DSD 128 with his then DAD AX24 at some sessions I was covering as a photographer for him.
He said DXD was still closer to the live sound we heard in the church.
But for those who prefer the slightly less resolved  a bit "softer and sweeter and beautiful" sound of DSD he  like several others also releases his albums as DSD .

 

[Christer]

  There's nothing wrong with criticizing a product but it becomes personal when you go after the creator of that product.  To suggest, as you have, that Rob has been either careless or incompetent in his development and testing of the DAVE can really only be interpreted one way.  This is, after all, a forum of gentleman and a certain level of respect is expected.  Look at any other DAC forum on head-fi or elsewhere and you are not likely to find one where the DAC's creator is as invested and gracious as Rob has been.  I think we each tune in everyday for Rob's pearls of wisdom. 
 
As for representing music lovers and consumers with limited funds, think about what you are saying.  What if you spent years designing and building your perfect house and you've poured your sweat and your soul into the project and then you decide to sell it for what you consider is fair market value.  Then some propsective buyer comes along and demands that you include the furniture and your personal automobile in the deal because he has limited funds.  First, the fact that he has limited funds is the customer's problem and not the seller's.  Second, he should be in no position to demand anything.  If he doesn't like the price, he should go elsewhere and see if he can find something just as good for less.  Considering the DAVE competes with DACs 10x its price, good luck finding something just as good for less.
 
Lastly, as you acknowledge that your understanding of digital theory is limited, you should be that much more careful with your demands and accept that some of Rob's design choices were perhaps made for good reason.  And as far as I am aware, Rob is not against hi-res, at least not against native hi-res PCM.  He just believes DSD as a format is flawed and not as good as PCM and he has explained very well his reasons for this.  Regardless of his beliefs, and as you have experienced for yourself, the DAVE is capable of superb DSD playback up to DSD512 through DoP.  As you wonder what other statements you might have made that could be interpreted the wrong way, just review your response to him when he indicated Davina would be capable of 16, 24 and 32 bit recordings and sampling rates from 44 to 768 kHz.  You seemed upset that Davina will capable of Redbook even though he indicated it would be capable of much more, up to 32/768.  Most people have no problems knowing that their USB 3.0 cable is capable of USB 1.0 transfers even if they never use it.  It's called backward compatibility.  I agree with you that classical music, perhaps more than any other genre, benefits from high sampling and dynamic range but there are other genres that don't and maybe never will and so Redbook is all that they aspire to. Would you buy an ACDC SACD?  Even diehard ACDC fans probably wouldn't.

Thanks for your parable and enlightened polite  way of pointing out my errors and rudeness.
Mea Culpa.
I will try to behave in a more adult  and civilized and  gentlemanly way in the future.
Then again a friend of mine recently told me when  we were entering a washroom for men. Chris it actually says  gentlemen on the door but don't let that stop you!

 

[Rob Watts]

Hmm, lots of questions today!
 
Firstly, I have not said that 44.1/16 bit is better than HD PCM (its easily better than DSD IMHO - and this is an important requirement - on my DAC's). Probably the best recordings I have is 192/24 - and generally, all things being equal, higher SR is preferable - but not by much. In principle - and note I mean in an ideal world - 44.1/16 is capable of very much better performance than we currently get - with a large enough tap length, you can recover the timing perfectly, assuming the ADC has zero (and I do mean zero) aliasing which currently the pro ADC's do not have - its as bad as -6dB!. Moreover, properly dithered 16 bit is capable of perfectly resolving an infinitely small signal - if you take an infinite period of time to do the FFT or correlation. So the format is capable of, again in principle, of perfectly reproducing the original timing information and perfectly capable of accurately reproducing very small signals.
 
But "you know nothing Jon Snow" is my favourite quote,and until you do carefully structured and rigorous listening tests, this quote applies. One of the interesting things about the Davina project is being able to decimate 705.6 k to 44.1 without any aliasing at all. Couple that with a long tap length WTA filter on the DAC, then I can actually hear the losses involved and be able to actively minimise them. The next question is the effect of bit depth, and how to treat truncation without degrading sound-stage depth, and this will also be a very interesting test. Now its very easy to do it for a 16FS signal (as in Dave), you simply use a 350dB noise shaper - but this is not an option at 44.1
 
On to the noise shaper - the 350 dB limit is technology limited (and its a very complex story), given that I am using 20 elements on the pulse array. I could detect a change going from -330 to -350, but frankly it was small. Any more depth to wring out? Perhaps. But by far the biggest loss is on the analogue power amplifier - the digital power amp will solve it (I know as the early prototype had amazing depth reproduction). Then there is the issue of the ADC itself, and again we have Davina coming to the rescue, as I have already designed the ADC noise shaper and this exceeds 350 dB.
 
I mentioned tap length, and yes I suspect that longer tap lengths will give better sound. But by how much? Frankly I do not know, and its possible its not much. I have mentioned 1M taps before, as this gets us to a sinc function with an accuracy of better than 16 bits - this then guarantees time domain performance exceeding 16 bits accuracy for a 16FS output signal. Unfortunately, the FPGA's capable of doing this are insanely expensive.... And I shudder at the design time needed to write close to 1,000,000 lines of code and verify the design, let alone getting timing closure on the FPGA....
 
Electrostatic direct drive from a single stage pulse array DAC? Funny, John and I were talking about it today. I think he thought I could design one in an afternoon....
 
And talking of Jon Snow - season 6 Game of Thrones - not long to wait now.... Much less time to wait than designing an electrostatic DAC/amp, that's for sure.
 
Rob

 

[Beolab]

The impedance of the Abyss is 46 ohms, so you would need to get to +5dB before Dave starts to clip. That would relate to only 150 mA at 6.8 v, so no where near the 0.5A current limit.

Rob

46 Ohms / 85 db in sensitivity .
I do not want to test where it clips because it can heart the diphragm in the headphones if the amp are clipping, and i find it more stressed if i go higher, but vol. - 1 is concert SPL rates almost with great control, it is just that it sounds very thin in the voices / instruments presentation, but with realy extended detailed bass when i go direct from the DAVE.

It is pretty remarkable how much power it can pump out / 0,5 Amps sounds like the double if you compare it to other amps that maxes out much erlier and sound harsh and stressed, with like 4-6 watts @ 46 ohms that is pretty remarkable!



So to all members; the DAVE can drive the Abyss actually very well to high levels no question about it !

If you want a meatier more hair chested sound with a slight less transparancy you have to buy a reference high powered Amp like the Headtrip or if you are in favor of tubeamps: Viva Egoista or the WooAudio 234 is my recommendation .

 

[mtoc]

  34 extra cores

 
Hello, what does the extra cores mean?