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Chord Electronics 2Qute DAC announced

Discussion in 'Dedicated Source Components' started by ok-guy, Jan 6, 2015.
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  1. Cenacheros
    It's great to hear that the 2Qute is so good.It would be great to hear what type of sound signature it has.I had originally planned to buy a Hugo.Given that I will only ever use a Dac at home,I've decided to pair a 2Qute with a seriously good 
    headphone amplifier and Sen.650s.
    I'm tempted by the Hugo TT,but at double the outlay it's a serious consideration.Thanks.
  2. OK-Guy
    Shanghai International High-End HiFi Show (SIAV 2015) 
    Date: 24th - 26th April 2015​
    Venue: SIAV 2015​
                 Shanghai International Exhibition and Convention Center​
                 2727Riverside Avenue, Puddong​
    Shanghai, China.​
    Booth number - 5T02
    Dita Audio (China) will be hosting Chord Electronics at the upcoming SIAV event - John Franks will be unveiling and presenting the Chord Hugo TT on Saturday 25th, also on display will be the Hugo and 2Cute with a multitude of differend sources.
  3. analogmusic
    the supernait 2 doesn't have this issue as the input sensitivity is better than the NAC 202
  4. analogmusic
    Dear Mr Watts thank you for your reply.
    I got my Hugo and wanted to give you my heartfelt thanks for your efforts in making this superb DAC. It is amazing. 
    I loved what it did from the minute it was playing music. As you said there is an extra octave of bass I didn't know my speakers was capable of producing.
    No harshness at all, and playing music is so much more enjoyable. Also the musicality is so much better now. I had many concerns and issues with my system, but the moment I plugged in the Hugo all concerns went away. 
    This is a major achievement and I hope you will keep on doing great work on your DAC designs. Thank you !
  5. analogmusic
    Dear Rob
    What is a OP stage? I understand discrete stage is better than op-amp, could you explain why? As I understand the Hugo has no analog volume control, so the output from the DAC doesn't go through a preamp (like one of the competing products from Salisbury)
    Also what is a pulse array dac? is it similar to Delta Sigma or the resistor ladder Dac?  Is the sound of the hugo due to the filter or due to filter/dac combination? Also if you were to use this filter with a conventional resistor ladder DAC would it work?
  6. analogmusic
    Dear Rob
    The olimex won't work on HD USB input? The Hugo sounds so good already I don't find any need for anything else !
  7. gad1
    The squeezebox touch is compatible with the Chord Chordette QuteHD
    according to a post on audiokarma.  Is the 2Qute similar enough
    to assume it also would be compatible with the sbt?
  8. WhatsUp

    Quick update. The Teddy PSU arrived and it immediately cured the RF symptoms I was experiencing with the wall wart from the CuBox. Having been listening with the wall wart for a week, I was quite used to the poor SQ, which was most noticeable with well mastered recordings with high DR but barely noticeable at all with contemporary "LOAD" recordings with low DR. I think the type of music people listen to and their systems transparency and frequency response may explain the varying experiences I've read on this and other forums.
    In any event, I hadn't expected to need to buy a linear PSU for the player, but if it means I'm able to enjoy the 2Qute to its fullest then its no big deal. A great DAC and loving it playing some well produced native DSD material. Simply stunning SQ.
  9. dgently
    About the Squeezebox driver, I undestand that the Qute HD needed a driver in general, whereas the 2Qute is UAC2 compliant. The 2Qute SHOULD work without a hitch with the squeezebox touch EDO, although I haven't tried it (my SBT is in storage). It certainly doesn't have any problems with other linux based systems I have tried.
    BTW I have tried several UAC2 dacs with EDO, and the only ones I had problems with were Concero HD with early firmware(which they fixed quickly), and the Asus muses, which needed a kernel patch for all my linux systems. I actually had to compile my own EDO kernel for this one, but it had the problematic C-media chipset. I really doubt that the 2qute will have any problems.
    As for the sound of wallwart for the computer, I don't think it has to do with just transparency in the system. I clearly hear changes in cables and dacs in my system. Maybe the Cubox has a particularly bad power supply (I use the Wandboard which has the same chipset but is otherwise different). Also, my wallwart is oversized (larger than needed) as none was included with the board. I also find it sounds somewhat better than my oppo 103 -> Lifatec optical cable.
    In any case they both sound great. Did have to play with the placement of my speakers (compared to my yulong) so optimise soundstage. Funny how different dac want different placement...   ...something about the timing I guess...
  10. Randle81
    Has anyone got the 2Qute grounded using the little screw on the box and heard any difference?
  11. HumanMedia

    The Squeezebox Touch will definitely work via Optical or coax SPDIF.
    However Squeezebox via USB didn't work with the QUTE HD or EX, but USB might work with 2Qute via a hub or with a particular EDO file. Slim chance but might.
  12. WhatsUp

    As I've already said, I tried two other wall warts plugged into a different mains radial from the hifi, both delivering 5v, 3amps, which is more than sufficient for my version of CuBox which draws 2amps... Same problem. Unless the RF is airborne, it can only be getting into the 2Qute via its USB cable.
  13. Rob Watts
    Welcome to Head-Fi analogmusic, and I am pleased you are enjoying more musicality from your music with Hugo - which is what this is all about!
    What is an OP stage?
    OP is output, and it replaces rather poor OP stages within op-amps. When faced with designing the electronics of Hugo, I had no experience of designing headphone amps - looking into devices that supplied headphones, they were very poor. So I designed it as if it was a power amp (I've designed lots of those) and gave Hugo the ability to drive 8 ohm loudspeakers directly - which means lots of current - in Hugo's case I set it too 0.5A RMS. You will not get this current from op-amps or headphone drive chips, so I had to design a discrete amp. Now to get the best transparency there needs to be a single feedback path, so the discrete OP stage needs to be within the op-amp's global feedback path. Since the op-amps are very high gain bandwidth product devices (high speed), that meant designing a Class A OP stage with very low propagation delay, so that the circuit would remain stable. Now the op-stages in op-amps are pretty poor to awful, so when I got the first prototype I was very pleased at how good the OP stage sounded, and how much lower distortion was (particularly high order harmonics) - even when using the op-stage in DAC mode with easy loads. Indeed, I now use this arrangement all the time now, as it really improves the performance of the op-amp - that's why 2 Qute has it too. The OP stage is by far the weakest part of all op-amps and this is simply because one can use a decent Class A bias current, and very substantial OP transistors, so thermal stability is ensured. And yes, Hugo does not have an analogue volume control, so this means the analogue section is very simple (just 2 resistors and capacitors in the direct signal path). Simple analogue gives much more transparency.
    What is a Pulse Array DAC?
    This is not an easy answer, as its complex and of course proprietary. But firstly the history. I first started designing DAC's in 1989, when the first delta-sigma bitstream devices from Phillips came out - these were DSD 256 DAC's (or PDM dac's). Now they were quite musical, but had technical and SQ problems - but they had very good low signal performance, and analogue distortion characteristic (small distortion for small signals unlike R2R DAC's which have more distortion for small signals due to glitch energy and resistor matching problems - issues that are impossible to solve). The biggest problem was limiting of resolution - unlike PCM, where ultra small signals are buried in the dither and so perfectly preserved, with delta-sigma the noise floor is a cliff edge for low level signals - any small signal below the resolving power of the noise shaper is lost forever. To overcome this, I used 8 PDM noise shapers with different dither, and summed the output in the analogue current to voltage converter (I to V). This gave much better performance, but I knew that much more was possible. So I started creating my own noise shapers and DAC technology using FPGA that were just becoming available (1994 now). What I needed was much higher resolution so the noise shaper OP is 5 bits not 1 bit, and I ran the noise shapers at a much higher rate - 2048 times not 256 times. Running at a faster rate means that you have more permutations of OP, which translates to much better performance. Run a 5th order noise shaper at ten times the speed, you can get in the digital domain, up to 100 dB lower distortion and noise - that's a 100 dB improvement in small signal resolution, so running at much higher rates gives massive improvements in SQ and measurements. Twenty years on, and I am still the only silicon/FPGA DAC designer running as high as this rate - delta-sigma DAC's are still stuck at 256 times or below.
    But changing from single bit to multi-bit noise shaping may throw the baby out with the bathwater. The primary benefit of single bit is that it can (if you are very very careful) have zero small signal distortion, as there are no resistors to balance, as there is only one. With 16e Pulse Array, there are 16 PWM elements, and each element has on the long term exactly the same data, but instantaneously slightly different data. The benefit of the Pulse Array scheme is that when the elements are slightly different in value, it creates a fixed signal independent noise, and absolutely no distortion, but has innately higher resolution of 5 bits. That's why Hugo has (uniquely compared to other non Pulse Array DAC's) no measurable distortion, or any other artifact, for signals below -30 dBFS (see plots in previous posts). Additionally, because of the way the array is composed, master clock jitter has no significant affect - random jitter gives a tiny insignificant fixed noise. Its why I don't go endlessly on about femto clocks as the DAC is innately jitter insensitive. There are many more problems with noise shaping, as it is a very complex subject, but this will give you a flavour of the issues involved.  
    Is the sound of the hugo due to the filter or due to filter/dac combination?
    The sound of Hugo is down to lots of things, but of course the primary problem that Hugo addresses is the time domain one. That's where we are converting the sampled data into the original un-sampled continuous analogue waveform - the original signal at the ADC sampling point. Now we are trying to re-create the original un-sampled waveform - re-creating all the missing bits of data from one sample to the next one. Now the theory is very straightforward - if you use an infinite tap length FIR filter with a sinc impulse response you will absolutely and perfectly reconstruct the bandwidth limited signal - if its perfectly bandwidth limited to below 22.05 kHz it will not matter if you sample at 22 uS or 22 femtoS it will make no difference to the output - if you use an infinite tap length FIR filter. Now of course, we can't have infinite tap lengths filters, we have to make do with something very limited.
    The question is, what level of time domain accuracy do we need where improving it makes no difference to the sound quality? That's where lots of careful listening tests comes in, as nobody knows. And its where I have been spending a lot of time over the last 18 months working on project xxxx - and I have learnt a lot (and I still have more things to discover, I am sure that I have not gotten to the bottom of the time domain accuracy barrel). What is clear to me, is that the ear/brain is amazingly sensitive to tiny time domain errors - there does not seem to be a level which one can say is insignificant. This is one of the really weird and interesting things about correlating what one hears with real signal errors - the other really odd issue being the perception of sound-stage depth - this can be upset by seemingly impossibly small errors.
    This is where I find the "DAC bit perfect" concept  - like a cheap politicians sound byte - ridiculous. The job of a DAC is to reproduce the continuous waveform at the ADC sampler - NOT to bit perfectly reproduce the sampled data with all the sampling time domain errors perfectly intact.  
    If you were to use this filter with a conventional resistor ladder DAC would it work? 
    The answer to this is yes, but not as well as Pulse Array - the 16e DAC can reproduce 50 MHz sine wave albeit with 3% THD and noise! The problem with R2R is that the OP can't switch fast enough, as there are a lot of switches involved in the R2R ladder, so in practice you can't run them above 16 FS - but I can run mine at 2048 FS so the digital domain is much closer to the original un-sampled analogue waveform. There are lots of other problems with R2R - noise floor modulation, code dependent glitch energy, high distortion at small signal levels, and moderate distortion at large signal levels.
    I hope I have not confused things too much - but we are dealing with a very complex subject, and something which, after more than 30 years of intense work, I am still learning new things. Things are very complex when you dive into it, and the ear/brain is a remarkably sophisticated device - the illusion of listening to real sounds is a truly amazing brain construct, and its something we know very little about. But at the end of the day, the engineering that goes into Hugo does not matter, its the musicality that counts, so keep on enjoying music! 
    Chord Electronics Stay updated on Chord Electronics at their sponsor page on Head-Fi.
    https://www.facebook.com/chordelectronics https://twitter.com/chordaudio http://www.chordelectronics.co.uk/
    onsionsi, Mython and plakat like this.
  14. spu1
    Thanks Rob, very nice explanation!

    Concerning OP Stage, does that mean that the 2Qute could also drive headphones? (as it uses the HUGO OP stage). If not, what is the output impedance of the 2Qute then?

    (Should receive my 2Qute soon, I hope…)
  15. Rob Watts
    Yes its the same transistors but in smaller packages, and a smaller current limit (200mA). The OP impedance will be a bit larger than Hugo, but still fraction of an ohm. I have not tried it with headphones, it does not have a volume control - I just wanted the lower distortion and SQ that the OP stage from Hugo offered.
    Chord Electronics Stay updated on Chord Electronics at their sponsor page on Head-Fi.
    https://www.facebook.com/chordelectronics https://twitter.com/chordaudio http://www.chordelectronics.co.uk/
    onsionsi likes this.
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