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

Discussion in 'Portable Source Gear' started by Mython, Oct 14, 2015.
  1. rbalcom
     
    My personal preference has been to us an AK120 or AK100 based on its physical size being very close to the Mojo connected with a custom optical cable. The AK120 holds two 256gb micro sd cards, but the library has a limit of 10k tracks. It makes for a nice portable setup event though it is a little over an inch thick. I have also tried the Shanling M1 connected through USB. The M1 takes one 256gb micro sd card. I am not a fan of using the usb connection on the Mojo because of it issues and UI for M1 is not very friendly, although it is functional. The M1 is smaller than the Mojo making it a little tricky to mount the M1 with the scroll wheel accessible. Also, the M1 uses a USB C connector so finding an OTG short cable is not easy. I'm not crazy about scroll wheels for navigating large music libraries so the M1 will not replace the AK120 for me. Hope you find my opinions helpful.
     
    Light - Man likes this.
  2. GRUMPYOLDGUY
    The color indicator/volume problem isn't really a problem. Just start the Mojo in preset mode and count clicks to get to the right output level.
     
    Preset is 3Vrms, each click is 1dB... Here's a summary of the math to get to your desired dB SPL level...
     
    You need to know two parameters about your headphones:
     
    Nominal sensitivity (dB SPL/mW) 
    Nominal impedance (Ohms)
     
     
    Step 1: Calculate sensitivity as dB SPL / 1 Vrms
    Y = y0 + 10*log10(1000/Z)
    y0 = headphone nominal sensitivity (dB SPL/mW), Z = headphone nominal impedance
     
    Step 2: Pick a target volume (dB SPL) and figure out output level needed to achieve it
    V = 10^((T-Y)/20)
    V = target level (Vrms), T = target loudness (dB SPL), Y = calculated sensitivity
     
    Step 3: Loss due to Mojo output impedance
    Loss(dB) =  20*log10(Z/(Z+0.075))
    Z = headphone nominal impedance, 0.075 = Mojo nominal output impedance
     
    Step 4: Find how many dB down the target level is from the preset
    L = 20*log10(V/3) - Loss(dB)
     
    Simply round the number above to figure out how many clicks from the preset you need to go. 
     
    I created a little spreadsheet to calculate the right levels for directly driving headphones from the Mojo... 
     
    headphone_screenshot.png
     
     
     
  3. RPB65

    Really? pmsl. I am 47 and yet to find one more of those kind of deals having looked for 20 years. The Mojo has been one of those deals for me, my Toxic Cable is another.
    Nothing is cheaper here than the USA. Just doesn't happen and if it is cheaper then the quality is rubbish compared with the imported stuff.
    I bought a leather briefcase from Emil Erwin that p1sses all over anything I could get here, even with 20% VAT and import duty added. The quality of a handmade item makes it so. Incredible bag.
    Good quality leather bound journals with awesome fountain pen paper, I buy these from Japan and the USA. Nothing here even compares to the workmanship of what I can get there.
    Leather wallets - guess what? Yup, USA and import them. I get what I want made by people who care about what they make, passionate about it and I love this about all of the stuff I buy.
     
    Give it up for a bad job here. In the UK no one has the skills or passion to do it. I will keep buying from abroad and importing. 
     
  4. Arpiben
     
    Your initiative is appreciated.
    Since Rob Watts clarified the lowest value of Mojo -77dB, one may add a column giving the number of clicks from that point too.
     
    Cheers [​IMG]
     
  5. GRUMPYOLDGUY
     
    77dB below the preset (3Vrms)? If so, simply add 77 to the last column. 
     
  6. howdy
    Just received the Mojo a few hours ago and is charging. Does the Mojo generally come dead? mine would not turn on but, when i plugged it in all the balls light up and the white power source led illuminated.
     
  7. Mediahound

    I think so. Although they say to charge it before using, I used it while it was charging the first time and there were no issues, it just took longer to charge. 
     
  8. miketlse
    Please note: Instructions advise charging a brand-new Mojo for 10 hours before using, but actually, it is only necessary to charge until the tiny white charging LED goes out. With most brand-new Mojos, this will be around half that. Just trust what the charging LED tells you.
     
     
    For a Mojo that has already been charged previously:
     
    Quote:
     
    When the first batches of Mojos were produced, Chord had no idea how fast they would sell, so they half charged the batteries, in case the Mojos spent several months on the dealers shelves.
    It was assumed that any Mojos that had been in stock for several months would require close to the full 10 hours when bought and first used.
     
    In practice the Mojos have sold as fast as Chord can manufacture them, so I doubt if any Mojos sit on a dealers shelves for long. Consequently the risk of buying a Mojo with a fully depleted battery has become near zero. This means that buyers can use their new Mojo as is, without charging, however I think that there are some posts relating to the benefits of fully charging the Mojo before first use, because it does ensure that the battery charging electronics, calibrate themselves correctly. 
     
  9. Mediahound
    I used mine the first time while the white charge light was on. Nothing blew up. 
     
  10. krismusic Contributor
    How's your battery life?
     
  11. Mediahound

    Seems really good athough I haven't measured it specifically. 
     
  12. Deftone
    i had my mojo plugged in pretty much 24/7 for 2 months at one time when it was on my desk. i still get 9 hours battery.
     
  13. waynes world
     
    That's good to know. I've being trying to restrain my lust for the Mojo because they are not cheap for Canadians. But the lust carries on! I'm keeping my eyes on the for sale forum. I usually don't like buying used "battery dependent" items (like portable amps or daps) due to loss of battery effectiveness (depending on how many hours were put on them). But due to the CN$ price, I may have to make an exception for the Mojo. Which might be okay since (a) it would mainly be used for my desktop (and therefore plugged in), and (b) it seems like the Mojo battery is not dying on people and (c) I think I read that the battery could be replaced if/when required down the road.
     
  14. aaf evo
    I'm looking into buying one to pair with my SE846/iPhone 7. I can't help but feel it's just not necessary though. Someone convince me to get one!
     
  15. jmills8
    Sound wise a solid yes.
     

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