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Chord Mojo DAC-amp ☆★►FAQ in 3rd post!◄★☆

Discussion in 'Portable Source Gear' started by Mython, Oct 14, 2015.
  1. canali
    I just spoke to blue moon, following up on my email about the butt plate....they have no idea either about an ETA either...they call frequently for updates, too.
     
    simonm likes this.
  2. Mython Contributor
    For anyone who arrived at this thread in recent weeks, never having seen JF's remarks about the forthcoming hollow module for Mojo, here they are:
     
     
     
     
    Quote:
     
     
    As far as I know, Chord are still aiming to include a few cables, but I guess it depends on how viable it proves to be to get reliable suppliers, so we'll just have to wait and see.
     
     
    .
     
    canali likes this.
  3. Dexter Morgan
    I think it's great for new users that the module will be coming with cables, but I wonder if Chord would consider selling a cableless version at a cheaper price for those of us who don't need them.
     
    simonm and headmanPL like this.
  4. Ike1985

    The suggestions I've seen in the last few pages are the best I've seen an I've been following this thread since page one. What you want when pairing with a smartphone is:

    1. Right angle
    2. EMI/RF elimination
    3. Length-find out how much length you need and cuatom makers will typically make to the length you want for a fee. Stacking tends to increase EMI/RF, consider that when looking at cable length.

    Also, if you have android you want an OTG micro-b to micro-b cable. With apple phones you need a CCk adapter. There are custom cable makers who make cables for apple phones that eliminate the need for a seperate CCK cable.
     
  5. Ike1985

    Or just cables for those of us looking for just cables.
     
  6. Solarium
    I got my Mojo yesterday, and have been comparing to my iDSD micro. I hear what people refer as "musical" and "emotional," but I want to understand why. The iDSD sound more flat, more monotone almost compare to the Mojo. Is the Mojo more true to the original sound? I'm not sure, but it sure sounds more fun. It's almost like describing a picture, the Mojo has more contrast and vibrancy, where as the iDSD has a more flatter, but possibly more true color.
     
    Then there's the matter of warmth. The iDSD is known for its warmth, yet that warmth has a bit of way veiling the sound. Mojo also has a hint of warmth, but that warmth is applied without extra veil. I'm in no way dismissing the iDSD, as it is absolutely superb, and perhaps more neutral. But the Mojo just sounds more exciting than the iDSD. I'm comparing using both my HD800 and the Mainline as amp, as well as my SE846 directly plugged into the Mojo/iDSD unit.
     
    One thing for sure though, the Mojo is much more compact and portable than the iDSD. Too bad I'm not using them as portables and strictly as desktop DAC's. The iDSD is more desktop friendly and allows easier charging while being used. I haven't tried both charging the Mojo while it's being used, but I read that it uses battery faster than being charged, being in the desktop mode. Since it has more settings, the iDSD is also more compatible with a wider range of headgear, be it IEM or high impedance full sized headphones. I just love the build on the Mojo though, it's truly a work of art.
     
  7. joshnor713
     
    I've had the iDSD and got the Mojo a couple weeks ago. I'm struggling a bit with my preference. You're right on point about the Mojo being more musical and engaging. I instantly became in love. However, I went back to the iDSD after a couple weeks with my new toy and am giving the Mojo second thoughts. The iDSD sounds more detailed and cleaner to me. I'm an analytical listener, so I value those things.
     
    But of course, at this point, we're talking about subtleties. I think it mainly comes down to usability, and like you said, the Mojo is a lot more portable. Although, there are a couple things about the Mojo that I dislike: the lights that you can't turn off, the slow charging, and that it runs hot. 
     
  8. Solarium
    The point about usability is spot on. The sound signature is a matter of preference more.
     
    One thing about the Mojo though, is that I can't get Equalizer APO to work with it. There's no enhancement tab under the sound settings in windows 10. Is there a work around?
     
  9. jmills8
    Then go for the Hugo.
     
  10. joshnor713
     
    If only it weren't 4x the price of the devices we're talking about [​IMG]
     
  11. TheTrace
    Is there going to be a Bluetooth module? I believe I saw it briefly mentioned somewhere in this thread in the past.
     
  12. x RELIC x Contributor

    The differences you describe are likely down to no noise floor modulation and MUCH more computational power in the Mojo. If you want to understand what Rob Watts has done with the Mojo compared to conventional chips like the one found in the iDSD I highly recommend you read the informative posts section, among others, made by Rob Watts in the third post of this thread.

    The reduction of noise floor modulation is directly related to perceived depth in the recording, as Rob has discovered in his many listening tests, which is actually very hard to achieve. Off the shelf chips usually exaggerate the details while the Mojo is smooth, yet Mojo presents the same amount of detail, but more layered, more natural to life, not like everything is heard on one plane. This helps our auditory brain make more sense from what it's hearing and it just feels right.

    To your point of the drive ability of IEMs to full sized cans the Mojo has the same power as the Hugo and drives both IEMs and headphones very well. Chord had a new battery developed for the Mojo for thermals and power density to achieve these results in the size of the Mojo.
     
    Mython and Solarium like this.
  13. UNOE
    Bluetooth module that used aptx or better would be very nice using optical.  I would buy it.
     
  14. Rob Watts
     
     
     
    Relating sound quality to technical performance is very complex, and I will try to explain, but I could talk for days about it and completely confuse everybody. But here is a quick answer to your questions.
     
     
     
    Musicality and emotional is complex, but in a nutshell its about removing distortions that interfere with the brains ability to understand the music. Conventional DAC's have a number of distortions that make it much harder for the brain to perceive the sound. Now we underestimate what the brain does with hearing, and simply make the assumption that the ears convert sounds into nerve impulses, and that's that job done, the brain simply access's the nerve signals. But that's not what happens - audible reality is an illusion created by the brain, and a considerable amount of brain processing is employed to create that illusion. So for example, you listen to a guitar and a singer for example. The data the ears feed the brain is a jumbled up mess of information, and the brain separates this mess of data into two distinct entities - the guitarist and the singer, and you perceive this as two separate entities. Not only that, but the brain very cleverly calculates where in space those entities are, and it does this from subtle timing, amplitude and resonance cues from both ears. But this requires considerable calculation. Moreover, small and subtle distortions (by saying distortion I mean anything that changes the original signal in any non linear way) interferes with the brains ability to separate sounds out into distinct entities, and interferes with the brains ability to place entities in space. This has two consequences for being able to enjoy music - firstly the brain is struggling to process the data, so has to work harder - which means you get listening fatigue, and so you can't enjoy the music. Secondly, being able to enjoy the music means being able to perceive what is going on - and there are many distortions that disable the brains ability to perceive the music. This is where it gets complex, as there are a myriad of different distortions that upset the brains processing. That's why Mojo has the WTA processing, why it filters and over-samples at 2048 times, why its got noise shapers that are a thousand times more resolving than conventional noise shapers - I could go on.
     
     
     
     
    The perception of depth information is down to very small amplitude differences of small signals. Now the brain calculates depth from a number of different cues, but most of it comes from the reverberant sound from the acoustic the recording was made in (or depth is added by adding artificial reverb). Now reverb is very small signals, and the amplitude accuracy of these small signals is crucial for the brain's ability to calculate depth. Now there is something very strange about depth perception - and that is the brain needs these small signals to have perfect amplitude linearity. If a small signal is slightly larger or slightly smaller than it should be, then the brain gets confused and can't calculate the depth properly, and things then sound flat. But the amazing thing is, there appears no limit to how accurate these small signals need to be in order for the brain to not truncate or flatten depth. In order to accurately reproduce depth you need extreme small signal linearity. You can't do this with R2R DAC's, as the resistors can't be matched. With DSD or delta sigma (Mojo is delta sigma too) the problem is now how well the noise shaper functions. As a signal gets closer to the noise shaper noise floor, the levels get smaller, as a signal that is smaller than the resolution limit of the noise shaper is truncated. To overcome this you need to have very high resolution outputs, with a noise shaper that has very high resolution - in Mojo's case, the noise shaper has a thousand times more resolving power than conventional high end noise shapers, and ten thousand times more resolution than DSD 64. But there is another source of error that can upset sound-stage depth and this is digital noise adding to the analogue signal. This applies to all DAC's, and is a big problem with chip DAC's, as there always exists a path from the digital noisy part to the analogue part, and this noise corruption will degrade the small signal non-linearity. But with Mojo the actual analogue parts are discrete, so its possible to eliminate digital noise from corrupting the signal. There is another mechanism for depth to be truncated, and this is with metal to metal interfaces. When you have a soldered joint, or any metal to metal interface, oxides and impurities concentrate at the interface. This oxide barrier is non-linear in that the resistance to small signals is larger than with big signals - so again we have small signals being attenuated. To reduce this problem you can only do this by reducing the number of passive components in the signal path. Conventional DAC's (delta sigma and R2R) have very complex analogue components, due to the need to convert from differential to single ended and to filter the high amounts of RF that comes out of a conventional DAC. With pulse array (my DAC technology within Mojo) this is not an issue as I can get single ended to work, and it runs at 104MHz, so little analogue filtering is required.
     
     
     
     
    I think here you are referring to timbre - the tonal colour of the instrument. Now timbre is an issue with timing reconstruction, as the brain uses transient information to infer the timbre of an instrument. Now conventional digital has uncertainty in the timing of transients (does a signal cross through zero just after a sample, or in the middle or close to the end of a sample?) and the only way of recovering the timing information perfectly is to use an infinite amount of processing on the interpolation filter. With the use of the WTA filter, which has been optimised to recover timing, and 500 times more processing than conventional DAC's, I can reduce the timing uncertainty - which results in much better timbre variation, so things don't sound monotone. There is another aspect in that noise floor modulation also affects timbre reproduction, but this is answered in your next question.
     

     
     
    Warmth or smoothness can be can be artificially created - for example with a dollop of 2nd harmonic. Mojo has very low levels of distortion, so its warmth is not down to doing this or other things. The key to true refinement with DAC's is noise floor modulation. This is where the noise pumps up and down with the signal, and all other non Chord DAC's have large amounts of noise floor modulation. Now noise floor modulation is a scary issue with DAC's, and there are countless ways that a DAC can suffer. Mojo, on the other hand has zero measurable noise floor modulation - the noise floor is at -170dB and it maintains this whether its output is 2.5v or zero, the noise is completely static. Now the issue of neutrality is a very complex thing, as increasing transparency will make it brighter and sharper, and increasing refinement will make it smoother and darker, and its possible to use distortion to create the impression of warmth or brightness. To be honest, I (or anybody else for that matter) do not know what the tonal balance of a perfect (and hence neutral) DAC is. And neutral cam mean different things to different people and with different gear!
     
    Mojo's musical performance is down to lots of technical things - way too complex to talk in detail with - but there are solid reasons why you hear what you hear, and why other DAC's can't do this.
     
    Rob

     
    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/
  15. Arpiben

    Hi @ Ike 1985,
     
      Your summary for pairing smartphones or even DAPs with Mojo through USB is quite correct.
    Since life is full of compromises, I would lijke to add the following:
     
    1. EMI/RFI:
     
    The main contributors for those Electromagnetic & Radio Interferences are the devices you are stacking together.
    In much less extent you may catch 'outside' or environment interferences through USB or even through the devices themselves. For sake of clarity I am only taking the case when both Mojo & DAP are working on batteries.
     
    A properly shielded and grounded cable first goal is to reduce the 'broadcasting' interferences from your devices.The second duty is to reduce external interferences.
     
    The shortest your USB cable is the less interference you may catch or transmit.
     
    In order to be efficient, the cable shield must be grounded and have no current (limited) circulating. DAC &  DAP are the ones providing (or not) the ground to the cable.
     
    Usually, in electronics,  one polarity ( often minus/negative) is connected to the Ground/Earth and eventually the metalic case of your unit.
    The devices you are stacking have different batteries meaning different voltage potentials that are equalized by the USB cable shield together or not with metalic cases touching each other in stack mode.
    This is for saying that EMI/RFI can "circulate" from DAP to DAC or vice versa even if you have a good  shielded cable.
     
    The only way to get ride of those issues is to use galvanic isolation at both ends. But smartphones/DAPs and portable DACs logically have not. 
    And even if they had, imagine you stack a plastic case smartphone on top of a plastic DAC....
     
    Whatever are those above considerations, and whatever is your USB cable stack configuration, Mojo, IMHO is filtering very well those EMI/RFI.
    In my portable usage , I do hear interferences from my phone but at a very low level.
     
    2. USB shield and angle:
     
    A good shielded USB cable is adding thickness and therefore stiffness and micro USB connectors constraints. Not all cables are done same but it is worth to keep it in mind.
     
    An angled USB cable has a better form fit but not sure at all it is removing constraints since it is difficult to have the perfect length tolerance when devices are not fixed.
     
    An angled cable in terms of impedance matching is normaly less good vs a straight cable ( impedance disruption at angle). But considering the lengths involved it should not be significative.
     
    3. Conclusion:
     
    As you see a multitude of parameters are entering into account for those issues.
    Therefore,IMHO don't put too much expectation in finding the "perfect USB cable" but rather try by yourself a few combinations it may work or not.
     
    Cheers
     
    Paulus XII likes this.

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