Chord Mojo DAC-amp ☆★►FAQ in 3rd post!◄★☆
Feb 19, 2017 at 3:46 PM Post #30,422 of 41,492

tretneo

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So I repurchased Chord Mojo a couple months ago after selling my original unit and missing it. Unfortunately this new one has a terrible coil whine while charging, my original unit didn't do this. I reached out to Chord support and they assured me this is "normal" but I really wanted them to do something to resolve it. They pushed me to work with the reseller however because the return period is lapsed they won't help me either. I've tried multiple chargers/cables but with no luck.
 
At first, this was only happening during charging and while the unit was off but now it is actually whining/buzzing during playback if power is connected. Basically this means quiet listening during charging is out since I have open headphones. Thoughts anyone?
 
/img/vimeo_logo.png 
 
Feb 19, 2017 at 3:52 PM Post #30,423 of 41,492

miketlse

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  So I repurchased Chord Mojo a couple months ago after selling my original unit and missing it. Unfortunately this new one has a terrible coil whine while charging, my original unit didn't do this. I reached out to Chord support and they assured me this is "normal" but I really wanted them to do something to resolve it. They pushed me to work with the reseller however because the return period is lapsed they won't help me either. I've tried multiple chargers/cables but with no luck.
 
At first, this was only happening during charging and while the unit was off but now it is actually whining/buzzing during playback if power is connected. Basically this means quiet listening during charging is out since I have open headphones. Thoughts anyone?
 
/img/vimeo_logo.png 

 
remove the power cable when listening, and only charge when you are not listening.
 
Feb 19, 2017 at 4:15 PM Post #30,427 of 41,492

WayTooCrazy

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@tretneo I just purchased one too... and it does the exact same thing. I've tried 3 different cables and even a Samsung charging brick to try and isolate from Power USB Hub. Still does it. I'm actually looking at an Anker PowerPort charger (someone mentioned it in the thread I believe) which should provided a "cleaner" charge to the Mojo and not provide the Coil Whine (will find out on Tuesday when it gets here)...
 
Feb 19, 2017 at 4:17 PM Post #30,428 of 41,492

tretneo

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  @tretneo I just purchased one too... and it does the exact same thing. I've tried 3 different cables and even a Samsung charging brick to try and isolate from Power USB Hub. Still does it. I'm actually looking at an Anker PowerPort charger (someone mentioned it in the thread I believe) which should provided a "cleaner" charge to the Mojo and not provide the Coil Whine (will find out on Tuesday when it gets here)...

 
Nice, thanks. Please send me a PM (if you can remember) and let me know if that does the trick. If so I'm willing to buy the Anker PowerPort as well.
 
Feb 19, 2017 at 4:19 PM Post #30,429 of 41,492

WayTooCrazy

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Nice, thanks. Please send me a PM (if you can remember) and let me know if that does the trick. If so I'm willing to buy the Anker PowerPort as well.

Sure thing.
 
Feb 19, 2017 at 4:26 PM Post #30,430 of 41,492

miketlse

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Is this an official solution from Chord? Their product can't charge and be used at the same time?

 
Read post #3 and the battery and charging section.
 
 
Quote:
Originally Posted by Rob Watts 
 
The noise is due to ripple voltage on the charger upsetting the inductors/capacitors within Mojo. If you use a clean quality PSU and a low resistance USB cable to the charger PSU the mechanical noise should be silent or insignificant. 
 
Rob

 
Quote:
Originally Posted by Rob Watts 
 
The problem is a noisy USB VBUS power line, and this makes the inductors in Mojo vibrate. Also, some USB cables have high resistance, and this makes the problem worse - so using a different cable can make the mechanical noise go away. The PSU itself can make it better or worse. Don't worry about it if you hear the noise, Mojo is not faulty and will continue to be reliable.
 
Rob

 
Quote:
Originally Posted by Ra97oR 

Further testing on the charger and cable compatibility. Chosen Anker PowerPort 5 for good measured performance and multi-port charging with Anker PowerLine due to good construction with braid + foil shielding. All are available at a reasonable price.


Case 1: Virtually silent, only heard very minor hiss when ear is pretty much on the unit
Case 2: Only noticeable hiss when you put your ears near the unit
Case 3: Loud whine lasting the only the first few seconds, faint charging noise after that.
Case 4: Loud whine, and it goes on for a few seconds and off for a few (voltage drop causing charging circuit to shut down)




Combo 1: Sony or Samsung charger + Sony or Samsung USB cable + extension cord = Case 4

Combo 2: Sony or Samsung charger + Any cable = Case 3

Combo 3: Apple 1A charger + Sony or Samsung USB cable = Case 2

Combo 4: Anker charger + Sony or Samsung USB cable = Case 2, slightly quieter than combo 3

Combo 5: Sony or Samsung charger + long 6ft Anker cable (same cable length as Combo 1) = Case 3

Combo 6: Apple 1A charger + Anker cable/Chord Mojo's bundled cable = Case 1

Combo 7: Anker charger + Anker cable/Chord Mojo's bundled cable = Case 1, slightly quieter than combo 6 directly compared, with no pattern to the noise (always the same loudness)



Anker PowerPort is tested at it's worse case scenario(unloaded), the ripple and spike measurements are better when the charger is fully loaded with devices. The Anker charger have noticeable more steady noise pattern than the Apple charger even with the best cable connected, the Apple charger's noise ripples in loudness and the Anker one is very steady at the same amplitude.



In short:

If you already have a Apple charger handy, just getting a quality USB cable like the one I've tested will yield noticeable gain, especially if you are using longer cables.

If you don't have an Apple charger, getting an Anker charger with their PowerLine cables will yield the best possible result without going to go with a lab bench linear power supply. Having a multiport desktop charager will also allow you to run shorter cables.

Link where I bought them:
Anker PowerPort 5: http://www.amazon.co.uk/dp/B00VTI8K9K
Anker PowerLine: http://www.amazon.co.uk/dp/B014H3GKZ4

 
Feb 19, 2017 at 5:10 PM Post #30,432 of 41,492

miketlse

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Samsung, Apple and Anker chargers have a good reputation on this thread, because they work fine for most users. Unfortunately there do seem to be small number of users who find that no combination of charger/cable that they try, removes the noise entirely.
 
For them the choices are:
 
  1. live with it
  2. unplug the charger when listening to music
 
Feb 19, 2017 at 5:43 PM Post #30,433 of 41,492

tretneo

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Samsung, Apple and Anker chargers have a good reputation on this thread, because they work fine for most users. Unfortunately there do seem to be small number of users who find that no combination of charger/cable that they try, removes the noise entirely.
 
For them the choices are:
 
  1. live with it
  2. unplug the charger when listening to music

 
I find it hard to believe that with such a wide behavior range Chord would take the position that they are, stating that this is "normal". Particularly as this is a device intended for high quality audio and this behavior goes counter to that. It's like some sort of quality lottery.
 
Feb 19, 2017 at 6:08 PM Post #30,434 of 41,492

miketlse

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I find it hard to believe that with such a wide behavior range Chord would take the position that they are, stating that this is "normal". Particularly as this is a device intended for high quality audio and this behavior goes counter to that. It's like some sort of quality lottery.


Bear in mind that it is Rob Watts who says that it is normal, and he is not a Chord employee.

How would Chord respond? The only way to find out is to ask, but John Franks does often display great generosity in trying to sort out issues for customers. :xf_eek:
 
Feb 19, 2017 at 7:07 PM Post #30,435 of 41,492

tretneo

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Bear in mind that it is Rob Watts who says that it is normal, and he is not a Chord employee.

How would Chord respond? The only way to find out is to ask, but John Franks does often display great generosity in trying to sort out issues for customers.
redface.gif

 
Ah ok, that makes a big difference then. Thanks Mike, I've sent a followup to Chord support now that the issue is happening during playback so we'll see how it goes.
 

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