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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. WCDchee

    Based on 5V maximum it should be up to 250mw thereabouts. Not to worry though the mojo can power just about anything :)
     
  2. TomGi
     
    Yes. Your Mojo is faulty as my first one. You should bring it back to get a new one.
     
  3. NZtechfreak
     
    Yeah, I'm aware of that (although my HE6 need more) - was using it with the LCD-4 over the weekend just gone, was just curious exactly what it was putting into them. Thanks!
     
    Checked - LCD-4 needs ~100mW to reach peaks of 120dB, so plenty of headroom. Another guy was saying he had the Mojo at max volume with the LCD-4 and was hearing clipping, which didn't match with my impression at all. Wonder how long his hearing will hold up given the volumes he listens at...
     
  4. sandalaudio
     
    Sound quality debate aside, I could use the Mojo to drive LCD-4 or HE1000 etc without sounding compressed or distorted, even on fairly quiet classical recordings. It had a bit more headroom in the volume position.
     
    Then again, I was at a shop last week and this guy was doing a demo on an HD800 with music so loud that everyone else thought that he forgot to plug it in and the music is coming out of the floor speakers.
     
    It told me two things:
    1. Some people do listen crazy loud without care, so we have to treat user reviews with a grain of salt. 
    2. HD800 sound amazing as a pair of loudspeakers.
     
    headwhacker and Feedbacker like this.
  5. WCDchee
    In fact, according to Shigzeo's measurements (if I didn't interpret it incorrectly), as you push the volume up, the mojo actually gets better. It's measurements at max volume are pretty sick.
     
  6. salla45
    Just listening to 70s Steely Dan on Mojo+K3003's. A very fine combination.
     
    There's just so much more happening within these well loved albums than ever I have heard before.
     
    Steely Dan were known for their obsessive production and perfectionism back in the 70's. I know these albums inside out. Top albums for me for the past 30 years. Regular replay.
     
    Pretzel Logic is really shining, really VERY 3d. There's some mad juju going on here.
     
    Night by Night's lead guitar has a texture I've never noticed before. Rikki Don't Lose That Number has that vibrophone intro to it, which I had NO IDEA continued into the main track. Never hear that before.
     
    Wow... it's really like listening to complete new masters of stuff...
     
    Go Mojo!!!
     
  7. Torq

    There are various audio players, and add-ons, that will automatically reset the output sample rate based on the track you are playing. "Bit-Perfect" will do it as an add-in for iTunes, then there are other players like Amarra, Audirvana, Fidelia, JRiver Media Center, Roon and so on that'll work either with iTunes, standalone or both (depending on the player) that will manage the output sample rate automatically.

    Having the rate set correctly to match the source file avoids having Core Audio up/down sample the file. Some of the players I mention above offer better resembling implementations. Personally I prefer not to up sample ahead of the DAC if I can avoid it.
     
  8. shigzeo Contributor

    That's a general measure of output. Signal to noise, stereo separation, etc., are directly related to pre-gain volume. 24-bit allows for more usable volume, that's it. 
     
  9. Rob Watts

    Because they can't using chip based DAC's. Chip DAC's have two current outputs. So you need two I to V converters (amps) then a differential to single ended amp, then a headphone buffer to deliver the current. You also need a lot of analogue filtering wrapped around these amps. So why are normal DAC's so complex in the analogue domain? Two reasons:
     
    1. Silicon DAC's are horribly noisy, as the substrate and grounds are bouncing around due to switching activity. So to counter this, it is done differentially, which means the ground noise is cancelled. It also hides the problems of the reference circuitry, which can't be made with low enough impedance on silicon. This translates to more distortion, and crucially noise floor modulation.
     
    2. Delta sigma converters run at low rates - best is at 12 MHz - this means that there is a lot of noise that must be aggressively filtered out in the analogue section. This also applies with R2R DAC's too as these have even worse problems due to the very slow switching speed.
     
    So to run with a single amp section you need the DAC to be single ended and to run the noise shapers at much higher rates to reduce your filtering requirements. Because the analogue section with Mojo is discrete, I can use extremely low impedance and low noise reference supplies - something that is impossible on silicon. This has the other benefit of eliminating noise floor modulation (actually there is a lot more to it than this as there are countless other sources of noise floor modulation in a DAC). To make the filtering easier, the pulse array noise shapers run at 104MHz - over an order of magnitude faster than normal. There are other benefits to running the noise shapers at 104MHz, principally the resolving power of the noise shaper. Now soundstage depth is determined by how accurately small signals are reproduced. The problem with noise shaping is that small signals get lost - any signal below the noise shaper noise floor is lost information. But by running the noise shaper at much faster rates you solve this problem too - indeed Mojo noise shapers exceed 200dB THD and noise digital performance - that's a thousand times more resolving power than high end DAC's.
     
    If I get time today I hope to publish noise floor modulation measurements showing Mojo has zero measured noise floor modulation. This level of performance does not happen on any other non pulse array DAC's at any price, and its the primary reason why Mojo sounds so smooth and musical.
     
    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/
  10. FALEEV

    So, does Mojo have better noise floor modulation measurements than Hugo or they are the same?
     
  11. obsidyen
     
    "Simplicity is the ultimate sophistication."
     
    Leonardo da Vinci. [​IMG]
     
  12. shigzeo Contributor

    Smart man that da Vinci.
     
  13. nntnam
     
    I would love to see more of measurement of the Mojo :D .
     
    I just pre-ordered it, has to wait until mid-December :frowning2: . Somehow it's out of stock everywhere in Japan... Hope my unit won't be so hissy with Fitear earphones. Hiss was the main reason I sold CypherLabs Theorem 720.
     
  14. AndrewH13

    Thanks Rob for such a detailed answer. And to others that replied.

    Better lock your code up Rob, under lock and key☺. Seriously though, with you being so open on all your discoveries in the digital domain, is there any worry of competitors copying, or replicating your code? Is it covered in a legal way, patent etc or is it that it would be impossible technically for others to use?
     
  15. shigzeo Contributor

    The Mojo's price point will be a huge deterrent to competitors that want to copy. It is finely machined, tight, and performs nearly flawlessly. Had I handled it and measured it without being told its price, I probably would have guessed around 1000$.
     
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