[Beolab]

I used to belong to the camp that believed MQA was a win-win for all but once you understand how it works and how it must take charge of the DAC for it to function optimally, it becomes clearer that this is not a good solution for all DACs.  With respect to the DAVE and the rest of Rob's DACs, to implement MQA would mean that the DAVE would have to stop oversampling for its own purposes and instead oversample for MQA's purposes meaning you can't have both.  

As for other DAC companies lining up to support MQA, there seems to be quite a lack of enthusiasm, don't you think?  Despite all of the traveling demonstrations over the past year and all the press at CES in January, nearly 6 months later, we still have only 3 DAC companies supporting MQA (2 if you don't count Meridian).  First of all, MQA won't work well on R2R DACs because of their inability to oversample to high levels so don't count on the likes of MSB or TotalDac signing up.  PS Audio has already come out saying MQA files actually sound worse on their FPGA DACs and so they have no plans to support it at all:

http://www.audiostream.com/content/ps-audios-paul-mcgowan-weighs-mqa#3FESB5qPGG90RqSM.97

Schiit has already come out saying they won't be supporting MQA either:

http://www.audiostream.com/content/schiit-audio-why-we-wont-be-supporting-mqa#zrBZQwdPcVMVCh2k.97

As for the friendly cigar Meridian smoked with Auralic, this deal appears dead because Meridian has decided their technology is best implemented at the DAC and not the server:

https://community.roonlabs.com/t/withdrawal-of-mqa-support/6730

As for MQA sounding better than standard 16/44, I would agree there is an improvement in the files I've heard using a Mytek Brooklyn DAC but the improvement in no way rivals what I hear with standard 16/44 on the DAVE.  Here is a review that came out earlier today by Michael Lavorgna that I find to be more balanced than the overly effusive praise thrown onto MQA by Robert Harley:

http://www.audiostream.com/content/mqa-reviewed#QhkzkSDLvM9cPKU2.97 

Perhaps the biggest reason you will never see (or care to see) MQA support on a Chord DAC:  DAVINA

Yes, i have no worries, in 5 years we know if this is the format to go for or not, its hard to judge today. The most of the brands are waiting for more content and for the Tidal MQA service, so i lend my 50 cents on the MQA format will be a big thing in 3-6 years time from now.

 

[NGSKGSncLWHmD9X]

 
I have a history of always being late on projects - even when I double the time it takes from my estimates... This is very true for cutting edge work, which has an element of research to it. So take what I say with a pinch of salt - so the PCB will be finished this month. Then it will probably be September before I get the prototypes. Then how long to get it working? I won't do test recordings till its perfect, so we are looking at the end of the year when tracks will get published - at the earliest. I am currently thinking of things to record, and the mic and equipment I need to do this. 

Rob

Rob,

I don't know if there are any designers out there who share so openly and willingly what they do like you do, but your openness on the subject is the exact reason why I probably am gonna go for a Dave.

 

[Mython]

   
Perhaps the biggest reason you will never see (or care to see) MQA support on a Chord DAC:  DAVINA

 
 
Yes, this has been my understanding, too, for some time, now.

 

[Crgreen]

For a numpty like me, can someone explain Davina?

 

[Mython]

Furthermore, although DAVINA has the potential to improve recordings for the entire digital-audio industry, I predict that DAVINA will massively increase sales of DAVE, because each will logically maximise the benefits of the other, up to the bleeding-edge of the state of the art.
 
 
@ Rob - I think it's really wonderful that you are about to create something (in addition to the already-wonderful DAVE), the combination of which will create a zenith in your career which will positively affect the entire industry, enormously.

 

[paulchiu]

For a numpty like me, can someone explain Davina?

 
Davina is Rob's ADC project.  Analog to digital converter.
I think Rob started talking about it here:
http://www.head-fi.org/t/766517/chord-electronics-dave/1785#post_12376871
 
Paul

 

[Mython]

.... can someone explain Davina?

 
Are you familiar with the benefits of Rob's approach to DACs? For example, the improved accuracy they offer, in relation to reconstructing subtle timing details and transients?
 
Even though Rob's DACs offer very impressive performance levels, in this regard, they can't fully overcome the limitations that exist in current ADC technology - so, if an analogue-to-digital converter in a mastering studio does a poor job of digitising music accurately, then no DAC currently available will be able to resolve all the timing errors created during the original digitising of the mastertape, in the mastering studio.
 
Rob's ADC project is intended to overcome a large proportion of the errors occurring during digitisation, so that a DAC such as DAVE will then have maximum opportunity to do perform its function to a very high standard, in creating audio reproduction of maximum realism (and Rob is also intending to subsequently explore a project for digital amplification, but that's some way off, and only secondary to the ADC project).
 

Spoiler: Digital Power Amp project

  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

 

 
 
 
In no particular order, and not directly pertaining to each other, here are some relevant quotes from Rob, about the DAVINA ADC project:
 

Spoiler: DAVINA ADC

 

   
Hi Rob,John, 
 
Great to meet you on the 1st day of CAMJAM Singapore. I have a Mojo for a few weeks and after hearing about your presentation on Mojo and Dave, I was keen to listen to Dave too. Good thing the local agent AV1 had one in the show.
 
The first time I heard Dave for a minutes, under show conditions, the sound quality was not obvious, as the setup of was different from mine: different can, Windows player, & different songs. 
 
So went back to listen to the Dave Dac next day for 30 mins using my MacBook, Audirvana+(no upsampling) , CD and DSD albums on a HifiMan HE1000.  
 
Wow. Outstanding sound. Best Dac I've every heard. Very transparent, lost of accurate details and very musical. This is my idea of what great music sounds like. 
 
The albums sounds so much closer to a live performance than anything I've heard before in Hifi .Couldn't stop smiling . 
 
So now I'm really happy with the Mojo, and using it every day to discover albums and hear music presented in life like way.
 
And also happy to know I've found what I can upgrade to in future - Dave.
 
Looking forward to your ADC too. Do get the code done soon and get it out. Can't wait to too hear well recorded music converted on your ADC and played back on Dave  
 
Rick 

 
Yes agreed - that's the sound of Dave - very real "your there" sound.
 
Me too on the ADC (project code word Davina), its a project that I have been working on for a long time (actually the first prototype was in 2001). There are a number of key things happening that conventional ADC's don't do well - noise floor modulation, aliasing, and noise shaper resolution. The noise floor modulation issue was solved way back in 2001. Aliasing is a major problem - normal ADC decimation filters are half band, so offer worst case only -6dB rejection. But I have used -140 dB decimation filters, and can still hear the effects of aliasing. Fortunately its not difficult to design a filter that has no aliasing, its just FPGA resources. On the noise shaper side, getting Dave standard (350dB) is not a problem, I have already designed that noise shaper.
 
We will be doing test recordings later this year, so I will publish test samples too on Head-Fi. I too am very excited about the sound quality possibilities of the ADC.
 
Rob

 
 

  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

 
 

  One of the good things about the Davina project is that I will have clear answers to these problems.
 
Firstly, timing. The problem that Dave is solving, and its a very important problem only due to sampling the music, is the reconstruction of the timing of transients. Now a bandwidth limited signal (that is zero output at 22.05 kHz and above), if you use an infinite tap FIR filter, with a sinc function for the coefficients, would perfectly recover the missing waveform that was within the ADC before it was sampled. So if we have a DAC that has an interpolation filter that was "good enough" - that is double the taps and you hear no difference, and halve the time from one OP to the next and you still hear no change - then we will be left with a perfect reconstruction filter, and the DAC will re-create the signal effectively perfectly before it was sampled. What we will hear is the bandwidth limited signal. Now my question is - will bandwidth limiting within the ADC change the SQ? This I will find out from Davina, and I can test this without using decimation, so I will know this aspect for sure.
 
The second issue is amplitude accuracy. Now depth perception requires zero error in small signal accuracy - the smallest error in amplitude, no matter how small, seems to confuse the brain, and so it can't calculate the depth correctly, and we then see a degradation in the perceived depth. Now with Dave the small signal performance of the noise shaper allows a -301dB signal to be reproduced perfectly - that's way better than 50 bits, and actually more like 64 bit accuracy. So how do I encode 64 bit amplitude linearity within a 16 bit system at 44.1? Will triangular dither do it? In principle it will. Normally I use noise shapers to guarantee 64 bit audio performance, but although this works at 768 kHz, it won't work effectively at 44.1 kHz. Again, this is an aspect that I will find out from the Davina project.
 
Rob

 

 

Rob, can I ask your thoughts on the distortions in digital audio itself - I think you touched on it before when you mentioned the idea of brain burn-in i.e. that the brain has to accommodate to the new types of distortions that have been introduced as a result of digital audio?

It seems to me that the introduction of digital audio have allowed new distortions to be created due to the fact that mathematical processing can be inaccurate in so many new ways that introduce new distortions which were never encountered before in the natural world of vibrating bodies

The sampling and recreating the original analogue signal without timing errors has been an extremely interesting problem for me over the last 3 years - mostly in the appreciation that extremely small timing errors can have a profound effect subjectively. What we are doing with ADC then back to DAC can be summarised:
 
Analogue continuous signal > Sampled data (ADC)> analogue continuous signal (DAC)
 
What I (and the rest of the engineering community) have failed to appreciate is how sensitive we are to very small errors in the reconstruction process. Mathematically its simple - we simply need an infinite tap length FIR filter with a sinc impulse response that also infinitely over-samples at the same time, then we will perfectly recover the original analogue signal in the ADC.
 
In practice, I do not know (for certain) how many taps are needed, and how much oversampling is needed - that said, I have made a lot of progress in this area, but I do not know how much further we can take it. It's one of the very interesting things I hope to learn from the Davina ADC project when I will be able to go from 768k, down to 48k, back up to analogue, and then appreciate how much losses we really get, and how to minimise them.
 
Very interesting times ahead!
 
Rob

 
 

 
 
.

 

[Crgreen]

I see, so it's primarily a technology which engineers can use to produce better digital recordings?

 

[Mython]

I see, so it's primarily a technology which engineers can use to produce better digital recordings?

 
Yes.
 
And (depending in what hardware format and on what pricing structure the ADC is eventually released) it may also be a viable option for audiophiles wishing to convert their own vinyl collections to a worthwhile-sounding digital format.

 

[Crgreen]

And such recordings will be compatable with MQA, which if I've understood it correctly, is a transfer and playback protocol?

 

[Mython]

And such recordings will be compatable with MQA, which if I've understood it correctly, is a transfer and playback protocol?

 
In what manner do you mean 'compatible with MQA'?

 

[rkt31]

more than vinyl, the Davina may give a new life to old master tapes. you may see several reissues of the classic albums depending how many music labels approach chord.

 

[romaz]

more than vinyl, the Davina may give a new life to old master tapes. you may see several reissues of the classic albums depending how many music labels approach chord.

I was listening to reel-to-reel yesterday in a 2-channel Audio Note setup worth more >$200k and it soundly beat the Audio Note CD transport + DAC (>$30k) that was part of the system.
 
The problem is the lack of titles.  You can buy some here but notice how many are available:
 
https://www.discogs.com/sell/list?page=1&format=Reel-To-Reel

 

[Crgreen]

In what manner do you mean 'compatible with MQA'?

The ordinary sense the word - there's no conflict bewetween the two technologies: recordings made using one can be played back with the other. Hopefully, my question is clear.

 

[Rob Watts]

Once Davina PCB layout is done, I will post some more about the project, and what I want to do technically with it.
 
Davina is really a technology proof of concept, as the pro audio market for a simple 2 ch. ADC is limited. If Davina works as hoped, then I will design an 8 ch interface (that's 8 ADC's and 8 DAC's in one unit) and this would then be the unit that the pro audio market would use.
 
I don't have an idea about how well the ADC tech will do commercially, and in one sense I don't care, as its more about achieving completely transparent performance than anything else. My overriding ambition is to be able to reproduce the sensation of depth accurately; I want to be able to reproduce a sound that was recorded 200 feet away, and it sounds exactly as if it was 200 feet away on reproduction. This ability to perceive space accurately is something that reproduced audio is clearly unable to do compared to real sounds in a real space.
 
I have no experience on recording; fortunately Chord has two guys that have a recording/pro audio background, and they have been providing advice for me on recording with simple two channel. Once the initial tests are done, then we have some pro audio specialists that will be working with us on evaluation and making their own recordings.
 
Another aspect that interests me is straightforward measurements - Dave already pushes the measurement envelope, so being able to do much better measurements from the ADC will be very useful.
 
Rob