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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. Fungus
    I think there is an amp in the mojo
     
  2. AndrewH13

    No amp as such, see Relic's reply above.
     
  3. Rob Watts
    Line level mode is just a volume preset for the volume control - nothing else changes.
     
    Mojo has an FPGA (which is digital logic only) a discrete DAC (turning digital signals to analogue via flip-flops and resistors) and a single output amplifier - and that is it.
     
    Conventional DAC headphone amps use differential outputs and have two I to V converters (current to voltage), a differential to single ended converter, and an output amplifier. Wrapped up with that is a analogue filter. So that's a lot of passive components and four amplifiers in the signal path. 
     
    Because Mojo's FPGA has extensive digital filtering (at 2048 FS) and has a noise shaper that runs at a very high rate (104MHz) and uses a discrete DAC, I can keep the analogue section radically simpler, and this is one reason why Mojo is so transparent compared to all other DAC amps.
     
    Rob
     
    Chord Electronics Stay updated on Chord Electronics at their sponsor page on Head-Fi.
     
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  4. vapman

    I guess my original quetsion, is all we can do is set Mojo to line level output, or is there a way to actully bypass the Mojo's amp and turn the outputs into true line OUT directly from DAC?
     
    Are DAC and amp integreated in the same chip?
     
    Lastly there is any chance of a non battery powered Mojo  to be released as a desktop only device.
     
    mojo desktop -> polaris -> yamaaha m4 could be amazing.
     
  5. x RELIC x Contributor

    I posted this a couple pages ago right after one of your posts.... In case you missed it:

    http://www.head-fi.org/t/784602/chord-mojo-the-official-thread-please-read-the-3rd-post/9300#post_12256340
     
    vapman likes this.
  6. xtr4
    I get the feeling that majority of new users of Mojo/Hugo still don't fully understand the design and fundamentals behind the what Chord has developed. Majority are still wrapped up in the traditional DAC is DAC, AMP is AMP era and still think that they are all discrete components.
    Even with the third post and various help by owners and Relic (who is awesome, btw. He deserves a special mention because of the effort he puts in to reply with patience all the repeat questions).
    Guys and gals (if any), it's not that hard to do a little bit of research first and read up on what's been posted by everyone that's been compiled in the 3rd post of the first page. I'm not saying that we can't be helpful and help our fellow head-fier but there comes a time when it does really feel that nobody ever bothers to read the first page anymore and just clicks to the last page to post a question.
     
    Sorry if I've ruffled a few feathers and stepped on a few toes but I feel that this needs to be said, especially for the amount of disservice for not reading the 3rd post when everything is compiled nicely for you.
     
    Mython and x RELIC x like this.
  7. vapman
    @xtr4 i understand the FPGA designs makes the dac and amp essentally the same... what im really trying to get at is, can the FPGA's amp functions be bypassed so it is used simply as a DAC, and the two 3.5mm outs are true line outputs to prevent double amping
    Paste

     
  8. x RELIC x Contributor

    Actually Rob should answer this, but the FPGA chip is a digital filter (not to make it combined with the amp, the FPGA filter is digital only), then there is a discrete pulse array DAC and from there to the analogue output. I believe what Rob is saying is that because of the Mojo's unorthodox DAC architecture it really kicks a** and there is no need to help it out in the analogue stage like most off the shelf components with a complex amp implementation. Because of this you can't really bypass what is neccessary in the single analogue stage.

    Above Rob already answered the difference:


    Mojo is much simpler than this. Mojo has one analogue stage in the path with very low distortion.

    Edit: Re-worded based on Rob's reply below.
     
  9. Rob Watts
    No, you need at least one amplifier to do the critical I to V conversion. Now it is possible to design a voltage only DAC (no amp at all), but they sound poor due to lots of problems - the largest being the huge amount of distortion you get doing it that way. Believe me, if I could make it simpler I would. The key that Mojo has is extremely low distortion and noise (0.00017% 3V 300 Ohms) but only one single amplifier in the signal path - and this amp combines headphone drive, filtering and I to V conversion in a single stage.
     
    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 x RELIC x like this.
  10. vapman

    Extremely well put & easy to understand. Many thanks to you!
     
  11. DMinor
    How 
     
    Have you compared this to a true line out (clean from dac) to an external amp designed with a DC servo thus completely getting rid of all the caps?
     
  12. vapman

    Perhaps that's the point i was stuck on. when he said the amp are one and the same as the dac, i didn't imaigne they were both part of the fpga. thus when i asked if anyone tried it with a separte amp with the mojo in lineout mode, seems they would be effectivly double amping.
     
    i plan to get this either way... i just want to know the clear picture on wherether or not true line out is possible :)
     
  13. Fungus
    will an ipod nano 6th gen work with the mojo? 
     
  14. Currawong Contributor
    You're over-thinking it. The idea of a "true line-out" came from the idea of bypassing the multiple stages of amping after the DAC in a typical device. These multiple stages don't exist in the Mojo, so you're getting, in effect, the very thing you're asking for with it. 
     
  15. xtr4
    Sorry vapman if my post seemed to target you specifically as it wasn't the intention.
     
    With regards to the double amping scenario, most head-fiers who have paired the Mojo with an amp have mainly done so to add a so called "flavour" to the sound signature.
    Example would be the Continental Dual Mono or any Tube amp, to add that special warmth. Or just the extra juice to really bring out the best of a hard to drive can like the HE-6. The double amping in this scenario is mainly just to tweak the sound signature towards something that the individual is accustomed to. YMMV.
     
    Hope this makes sense. 
     
    vapman likes this.
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