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

Discussion in 'Portable Source Gear' started by Mython, Oct 14, 2015.
  1. antz123
    I have a 1000$ odd music spend in mind. Out of which 300$ are towards Meze 99.
    Left with 700$ I have two options in my mind post talking to some people. Just wanted to some more information so thought shall ask for advice here.
    • Go for Mojo (550$) + around 200$ player probably a Shanling M1 or or Plenue D. It limits my music carrying capability but leaves me with an option to probably go for a better DAP 18-20 months down the line
    • Go for DAP upto 700$. In consideration are Pioneer (Onkyo rebadged) or Shangling M5.
    I have Dunu 2000 as my IEM and primarily listen to  classical rock and some modern stuff like Daftpunk or Nine Inch Nails , Foo Fighters etc.  I am not big on streaming, I rather prefer good neutral sound, nice sound stage,  battery life n storage capacity.
    Which option would you suggest to go with?
    Thanks ... sorry if this is wrong forum to pick on minds
  2. Miksu
    I have listened now to Hugo, 2Qute and Mojo with Senn HD600. Hugo was the best in terms of snap and resolution but got glare in highs I couldn't stand. Same goes now with the other two. Bought Mojo since it was told to be a bit more dark but still the same glare and hiss, especially with female voice s and f. I'm using laptop and USB connection with Audioquest Jitterbug (also tried without). Tested also with Gustard U12 USB to optical converter and with that bass goes away but glare stays.
    Since Chord DACs should be great according to all reviews there must be something wrong with my setup. Or maybe I'm too sensitive to highs? Any ideas what to try? There isn't any glare problems with some other DACS I've tested recently, but otherwise they haven't been on par with Hugo/Mojo.
    Spending money on a DAP when you're using the Mojo is superfluous. Those devices cost what they cost because of the board design, DAC, and analog components... When you hook it up to the Mojo, you are bypassing all of that. It becomes a glorified hard drive. You should either get the Mojo or a DAP, but not both. 
    If it were me, I would choose to go with the Mojo and an amp that attenuates the input (i.e. negative gain) so you can drive your IEMs without needing excessive digital attenuation in the Mojo. 
  4. headfry
    if you can eq the highs down a bit you should find the sound great;
    if course your playback sw needs to have an eq feature.
  5. RPB65
    Errrr, eh? lol.
  6. Miksu
    It's not a problem where overall level oh highs is too high, it's just sibilance or glare of some voices. Like listening to FM radio where station is tuned just a bit off. A bit hard to explain.

    What's wrong with that statement? Many amps designed specifically for IEMs have -10dB or less gain. Analog attenuation preserves the waveform, digital attenuation results in saturation.
    Peter Hyatt likes this.
  8. RPB65

    That was shorthand for me saying I don't understand what it means.
    Peter Hyatt likes this.

    Ah. I misunderstood.

    What I meant in my post was that since the OP has IEMs, he should get an amplifier that does the opposite of amplifying to pair with the Mojo. That way he can increase the volume on the Mojo and still use his IEMs. This is a technically better option than cranking the Mojo volume way down and plugging in directly.
    RPB65 and Peter Hyatt like this.
  10. antz123
    Thanks for your reply, actually am with  @RPB65 ,  do elaborate and help me grasp  the context better, please.

    I updated my post just above yours to clarify.
    antz123 likes this.
  12. GreenBow
    That's encouraging. I am not sure if it concludes that the Sony DAP does transmit bit-perfect.
    It does conclude that there is a either bit-perfect or a pre-set engaged when using the USB out. It may default to a particular EQ with no volume control initialised. Thank you for doing the test.
    I'd email Sony for confirmation, but who knows if they will write back the correct answer. (Plus I would probably have to tell them my house number and phone number just to access their 'Contact Us'.) 
    Sorry, my last few posts weren't particularly useful... Here's a better explanation.
    Mojo uses digital attenuation, where each click of the volume button results in a 1dB change in output level. Because it's done digitally it is effectively a scale factor applied to the audio samples:
    -1dB = 10^(-1/20) = ~0.8913x
    +1dB = 10^(1/20) = ~1.1220x
    Because we're talking about fixed point math here, there is some quantization error involved meaning these constants will not be exactly 10^(-1/20) or 10^(1/20)... but we can ignore that for the purposes of this discussion since it's ancillary to the real problem with digital volume control. 
    When we scale the audio samples, we have discrete control... This requires a crash course on fixed point math. If I multiply two 32-bit numbers with, say, 30 fractional bits, I need 64 total bits with 60 of those being fractional to store the result with no loss of precision. Of course this bit growth can get out of control really quickly, so we use rounding at strategically chosen stages that balance precision with area (i.e. resources in the FPGA). If we're using a 32-bit DAC, no matter what, we have to reduce samples to 32 bits. The problem is I can only get so close to 0 without actually being at zero... specifically 32'h1 (+1) or 32'hFFFFFFFF (-1). So even if the math says a particular sample should be even closer to zero than 1/2^30, I can't achieve it digitally. Consequently, I lose a bit of information (pun totally intended). 
    In the analog world this isn't problem... we have infinite control over amplitude from rail to rail and can get as close to zero as we like. Of course the reality is things like noise performance limit how small of a signal we can produce that is still meaningful, but that problem exists regardless of whether we use digital volume control or analog volume control. So analog volume control is the better option in terms of preserving information.   
    RPB65 and maxh22 like this.
  14. bikutoru

    IMHO Mojo and 2Qute(I use both daily) handle highs beautifully, no sibilance or glare of any kind. With Mojo I use three different headphones: NAD HP50, AKR K720, Grado MS1. Sorry, have no experience with IEMs, just some earbuds from time to time and they are fine too.
    2Qute is permanently setup with the speaker system and no problem there.
    The first thing I do with any piece of audio equipment is to put it through a couple of Opera recordings where high frequencies of human vocals show me if equipment clips or distorts(where I'd put glare and sibilance). Chord gear handles music across the board so well that now I have two of their dacs.
    I'd suggest to try a different headphone or couple and see. If you still have the same problem, it might be that your hearing is just 'over' sensitive to highs. What we hear is a very subjective thing. I notice that my brain can adjust so almost any sound-field, but with bad one it will get fatigued fairly quickly, with good like Mojo I can go 25 hours a day.
    Good luck with your experiment.
    Light - Man likes this.
  15. Miksu
    Thanks for the suggestions. I have two hps which work fine with other DACs so they should be ruled out too. Just came to mind to test with longer USB cable and that seems to help a bit. Maybe less interference from laptop now that is half meter away instead of few cm (inch). But not perfect yet.

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