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

Discussion in 'Portable Source Gear' started by Mython, Oct 14, 2015.
  1. morinu
    First 2 hours with the Mojo and it is blowing my mind with the HD600... I can't believe how good they are together... [​IMG]
     
    onsionsi likes this.
  2. Rob Watts
    The technically perfect impedance is zero, and that's why I worked so hard to get it as low as 0.075 ohms with Mojo.
     
    The reasons going for as close as zero are:
     
    1. Frequency response. The impedance of the headphone varies with frequency, and so by having a high output impedance will cause frequency response variations. Zero impedance eliminates this problem.
     
    2. Distortion. The impedance of a headphone varies with level, and having a higher output impedance will increase the total distortion - given that Mojo distortion is so low, this is actually quite a significant an effect. Again, zero impedance eliminates this problem.
     
    3. Damping factor - probably the most important reason. A drive unit is a resonant system - that is a mass on a spring - that is damped mechanically and electrically. Electrical damping is due to the headphone creating a current due to the motion of the driver in the magnetic field - and how well this is controlled depends on the electrical impedance the driver sees - in our case, the cable impedance and Mojo's impedance. Again, zero impedance gives the best damping, with an infinite damping factor.
     
    I did some listening tests many years ago with loudspeakers and damping factor and found that it made a massive difference to the sound. Damping of 10 gave a very soft, big fat bass - but everything sounding one note in the bass - simply because the loudspeaker was doing its own thing at the resonant frequency. Going from 10 to 100 gave a tighter bass, with much better pitch reproduction - you could follow the bass line much more easily. Above 100 to 1000 it sounded tighter - no big change in pitch (being able to follow the bass tune) but the perceived tempo of the music became faster as transients are much better controlled. Going above 1000 gave a small improvement in how tight it sounded.
     
    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 and Ike1985 like this.
  3. masterpfa
    We await your verdict
     
    Welcome to the club.
     
  4. masterpfa
    Just re-united my AK100 and Mojo after a period of using the Onkyo DP-X1.
    I had to do a double take as I thought to myself, I don't remember posting this picture 
    Same model, colour, case and interconnect only the headphone connected is different. I even have the same worktop surface (OK that laast one not strictly true) [​IMG]
     
    I had been waiting for my replacement Sys-concept cable.
    Now I have returned to the compact size stack I need for my commute.
    [​IMG] 
     
  5. Ra97oR
    tmp_28929-DSC_0329-2131605603.jpg
     
    This is how I currently have my Mojo as when I am carrying it around in my pocket.
     
    I feed it with my phone in a different pocket to reduce bulk.
     
  6. Currawong Contributor
     
    I don't have a Femto clock version of the M1 and was expecting zero difference between using it and the AK100 as the transport. However, much like I had with the Hugo, the best results I got sonically were with the coax input. In the Hugo's case, it was with Soundaware's D100PRO. I have no idea why, unless one of the devices has an output that isn't bit perfect. If not that, the only thing I could speculate is that the Hugo and Mojo's electronics have to perform less timing recovery and the internal electronics end up generating less noise themselves. 
     
  7. Joe Bloggs Contributor

    Actually, starting from an effective zero ohm impedance from the Mojo, there's a very cheap and simple "impedance module" for any CIEM or headphones: it's called a headphone cable / extension cable with in-line volume control. They put a variable resistor between the amp output and each headphone channel.

    Unfortunately I don't see such an "impedance adapter" ever becoming a HiFi item. Or do I...? yaywhatever-avatar.jpg
     
  8. x RELIC x Contributor

    What I found absolutely shocking was the clear and unexpected difference between the AK240 and the AK100 mk2 with the exact same optical connector.
     
  9. x RELIC x Contributor

    That would explain the difference I heard with the different cables included with the Sennheiser Momentum (v1.0) that I briefly owned.
     
  10. Multimediers
    https://item.taobao.com/item.htm?spm=5706.1529727.a31f1.4.SmNVtI&scm=1007.11502.21311.100200300000003&id=528390962477&pvid=5e6a9193-0115-4887-a3ba-6f1ee2d8530f
     
    not trying to help them ad. here but just an example from Taobao for available options of 3.5mm coaxial cable for Fiio Mk2s with Mojo
     
  11. WCDchee

    I know, same with the x5 and the m1pro, and they're both coaxial!
     
  12. x RELIC x Contributor
  13. Multimediers

    I am curious on this point, too. Anyway, it will not make any difference in performance.
     
  14. audi0nick128
    Interesting to hear about the Esther m1 (pro) and the reported experiences.
    I am not certain how these differences in SQ can be explained. But when Mr. Rob Watts says his DACs are immune to jitter I do believe him.
    That being said I can imagine other effects beeing responsible for difference in SQ. Rob mentioned disruptive currents have to be taken in account.
    This might explain a recovery reclocker to be effective when used with mojo. It might just be the cleaner power supply.
    So now it seems like the system to check out might be Esther-Mojo-Ether C
    Speaking of those stray currents again, did anyone test Mojo with a grounding device, like a entry level Minimus Entreq Grounding Box?

    Cheers
     
  15. x RELIC x Contributor

    The differences I heard was with an optical connection, which is immune to 'stray currents'. I really think that it's down to the way the player is decoding the file and perhaps (just a hunch) there may be DSP going on in some players that aren't being advertised. Of course, strictly speaking of what I've heard on my devices. RF noise and other 'stray currents' may affect other players, but I'm still doubtful it's jitter that would cause a difference.
     
    fluidz likes this.

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