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

Discussion in 'Portable Source Gear' started by Mython, Oct 14, 2015.
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  1. jamato8 Contributor
    Here is an idea form Sysconepts on a new crazy low profile cable but the cost is a lot more as it is labor intensive. You would need good fingernails or a knife edge to start it when taking it out of the sockets. You would never want to pull it by the cable but if you want ultra low profile, like almost no profile, the cable on the right would seem to fit the bill. 
     
     
    low_profie_Tolsink_to_MiniPlug.jpg
     
  2. Wyd4
    That is pretty awesome.
    Thing is I would want a low profile cable for pocketing things. But I reckon I would be scared to for fear of breaking it..
    Still very nice though
     
  3. jamato8 Contributor

    I asked Joseph  and the whole idea is that the ultra low profile would be for the benefit of portability and the cable would not hinder or get in the way of anything, which also means the cable is less apt to get damaged. 
     
  4. Duncan Moderator
    Hmm... Jealous of the ultra low profile cable - but, spent all my money this month on upgrading my PC :frowning2:
     
  5. Rob Watts

    Just to clarify:
     
    1. SPDIF decoding is all digital within the FPGA. The FPGA uses a digital phase lock loop (DPLL) and a tiny buffer. This re-clocks the data and eliminates the incoming jitter from the source. This system took 6 years to perfect, and means that the sound quality defects from source jitter is eliminated. How do I know that? Measurements - 2 uS of jitter has no affect whatsoever on measurements (and I can resolve noise floor at -180dB with my APX555) and sound quality tests against RAM buffer systems revealed no significant difference. You can (almost) use a piece of damp string and the source jitter will be eliminated.
     
    2. USB is isochronous asynchronous. This means that the FPGA supplies the timing to the source, and incoming USB data is re clocked from the low jitter master clock. So again source jitter is eliminated.
     
    So does this mean that any digital cable will do?
     
    Sadly no. Mojo is a DAC, that means its an analogue component, and all analogue components are sensitive to RF noise and signal correlated in-band noise, so the RF character of the electrical cables can have an influence. What happens is random RF noise gets into the analogue electronics, creating intermodulation distortion with the wanted audio signal. The result of this is noise floor modulation. Now the brain is incredibly sensitive to noise floor modulation, and perceives this has a hardness to the sound - easily confused as better detail resolution as it sounds brighter. Reduce RF noise, and it will sound darker and smoother. The second source is distorted in band noise, and this mixes with the wanted signal (crosstalk source) and subtly alters the levels of small signals - this in turn degrades the perception of sound stage depth. This is another source of error for which the brain is astonishingly sensitive too. The distorted in band noise comes from the DAP, phone or PC internal electronics processing the digital data, with the maximum noise coming as the signal crosses through zero - all digital data going from all zeroes to all ones. Fortunately mobile electronics are power frugal and create less RF and signal correlated noise than PC's. Note that optical connection does not have any of these problems, and is my preferred connection. 
     
    Does this mean that high end cables are better? Sadly not necessarily. What one needs is good RF characteristics, and some expensive cables are RF poor. Also note that if it sounds brighter its worse, as noise floor modulation is spicing up the sound (its the MSG of sound). So be careful when listening and if its brighter its superficially more impressive but in the long term musically worse. At the end of the day, its musicality only that counts, not how impressive it sounds.         
     
    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/
    onsionsi, JoePR31, Pokemonn and 13 others like this.
  6. jamato8 Contributor

    I know what you mean. I just ordered a regular 2.2 and then they come out with this. lol Well maybe sometime in the future, I don't know but I do like the ultra low profile but I have spent my money for now. 
     
  7. mscott58
    Did they say how much more the ultra-low profile cord would be? Cheers 
     
  8. Ike1985
     
    Wow thank you so much, hope to understand it all some day.  I will be using the MOJO with either the xperia Z5 or Samsung S7, can you suggest any good RF shielded cables for me since phones don't do optical.
     
  9. greenmac
    Anyone got any impressions of the MoJo with Audeze EL-8 Closed Version ?
     
  10. x RELIC x Contributor

    The highlit part in particular made my day. Great analogy!
     
    Barra likes this.
  11. sheldaze

    Though it's not the primary use, I have been using it with my EL-8 Closed.
     
    I have a portable USB DAC/AMP, which I am writing a review for - easy to provide an upgrade path, in the review, by listening to the Chord Mojo. And it is indeed fantastic with the EL-8!
     
  12. jamato8 Contributor

    I don't think they know for sure as they have to make a special mold and that will take a little while. 
     
  13. musicheaven

    Thanks Rob your explanation is quite thorough and just few hours ago ordered a glass based Toslink cable because of your preference of digital link between the DAC and the source, unfortunately I do not have a portable that has Toslink output and have to use a well designed RF shielded coax cable. I do not want to piggy back my smartphone onto the DAC because it creates too much RF I can easily hear and pick up. My basic explanation above was for an off the shelf delta-sigma DAC, your design is way more sophisticated than that and glad you're the brain behind it. What would be useful is to point the readers towards good digital interconnect cables even if it's not the preferred connection, there are just too many coax based players out there. Any suggestions for well made or DIY cables would therefore be welcome.
     
  14. Skyyyeman
     


    Thanks for your intelligent and lucid explanations. If you don't mind a related question:

    Clock jitter -- What is clock jitter? The reason I ask is that in considering different DAPs to use as transports to output a digital signal to the Mojo, I've seen some varying specs for clock jitter on different DAPs, as follows:

    AK100 90 ps (pico seconds)
    AK120 50 "
    AK240 50 "

    Question: Does clock jitter degrade the digital signal before it's send out from the DAP? Or are they referring to clock jitter of the internal dac, in which case clock jitter doesn't matter since the signal never reaches the dac (it's been output beforehand)?

    If clock jitter degrades the signal before it's sent out, then it appears that the AK100 is not as good a transport as the other two. But would the difference be discernible?

    Thx
     
  15. x RELIC x Contributor

    You have some reading to do. :wink_face:

    http://www.stereophile.com/reference/1093jitter/#F29RG2Kut5Wah1ZH.97
     
    Mython likes this.
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