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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. Libertad
    Are your mojos getting hot i used mine in a gaming session on warframe while using foobar2000 for music and it got really hot. Im using it while feeding it power from a 1amp charger is this normal?
     
  2. Takeanidea
    Totally normal nothing to worry about at all
     
  3. Torq
     
    Off the shelf DAC chips, which is what is in the vast majority of other DAC products, aren't necessarily intended to drive transducers directly and, as a result, will tend to have lower maximum output current and/or voltage swing.  Buffers and op-amps, or discrete equivalents (i.e. the "amp section") are then needed to accommodate more demanding loads. 
     
    Rob's designs don't use off-the-shelf converters so don't have the same constraints.
     
    Or that's my understanding of it at least.  For some reason I thought there was a series of discrete transistors in the Mojo's output section as well, but I could well be mixing things up and/or reading slides incorrectly.
     
  4. imattersuk
  5. Libertad
    thank you very much for the quick reply[​IMG] using optical out on my pc (fist time ever using it) and i have to say it sounds at least to me just ever so slightly smoother in a good way compared to usb
     
  6. x RELIC x Contributor

    I would echo what Torq said, but I'm not going to pretend to be an EE here. Being the designer of the entire device and not using off the shelf components has advantages to create a device with a specific design goal and to meet the challenges that are presented along the way. Rob said he had quite a few challenges with the Mojo design and it took some time to overcome them. I'm glad he stayed the course.

    As far as the actual analogue stage is concerned he said he used six small transistors in parallel instead of three large devices as being the only real difference in the OP stage from the Hugo. It's still not a seperate amp as is in traditional systems. It's much more simple.
     
  7. shigzeo Contributor
  8. prismstorm
    So it's entirely normal that when used as a DAC for iMac the Mojo's ability to display different colors according to sample rate differences is effectively disabled and it will simply forever be at the color corresponding to the maximum rate you set it on in the MIDI setup.
     
    Should I set it to the maximum (7xxHz) just for maximum leeway or just to 192 since that's the top rate for most tracks? Is there an advantage to picking one over the other or does it simply not matter. 
     
  9. lextek Contributor
    Versatile little thing. Just messing around with different sources. Sounds OK from the AppleTV. I'm sure the $2 optical cable has something to do with it, but not bad.
    image.jpg
     
  10. GoSUV
    I also have the Meridian Explorer and have explored (pardon the pun) "audio-quality" USB cables and other USB power solutions, and can confidently say that these things make a huge difference to the Explorer's sound quality. My educated guess in this is, since the ME is powered by the source device, it is dependent on the source's power cleanliness. The "audio-quality" USB cable alone should be designed differently than your $5 printer cable where the power lines are wound separately from the data lines, thus reducing whatever interference it may cause to each other. By adding special USB linear power, thus separating the dirty USB power from your source computer, will take things to another level. The improvements are so obvious that it doesn't take an expensive headphone for anyone to notice the difference.
     
    Now whether all these matter to the Mojo, is quite another matter. Since the Mojo has its own internal battery, all these external USB cable and power solutions should, in theory, not have any effect. I haven't been able to try out any of the so called "audio-quality" USB cables for the Mojo due to the lack of them with micro-USB terminations.
     
  11. joshuachew
     
    I am using the AK120 Titan via optical out and using the MH335DW.
     
    And as I stated, it is not hissing, it is a buzzing. It happens even when the Mojo isnt connected to any source, and it is more prominent on the right channel and its not very slight, its actually very noticeable and can even be heard in the opening of songs where the music is a bit softer (not just in quiet passages). Is this a defect? should I bring it back? 
     
  12. ClieOS Contributor
     
    Now to say it has no analog stage  or straight from the DAC might be pushing it too far. Even transistors are still analog stage, just perhaps no gain stage is involved (as it is taken care mostly in the digital domain as well as the DAC output) but only buffer stage is implemented. I'll think typically you will find other manufacturer describe this as having a 'discrete output', which means no opamp is used.
     
  13. x RELIC x Contributor

    ClieOS, I've always said its the analogue stage after the DAC. Not once did I say that it has no analogue stage. I said its different from 'typical' DAC/amp designs and it can't be bypassed in the Mojo (or the Hugo).

    Edit: Besides the transistors Rob said the Mojo is very much the same as the Hugo. You can read his take on his implementation here:

    http://www.head-fi.org/t/702787/chord-hugo/1830#post_10459450

    From his post in the link, apologies if I oversimplified:

     
  14. headwhacker
     
    Entirely up to you. 
     
  15. WCDchee

    I wrote up what I gathered from Rob on post 5198 :)
     
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