[Rob Watts]

The mechanical buzz is due to the USB charger being noisy. This noise modulates the PSU inductors, which creates the noise. The level of mechanical noise depends upon the PSU. If you use a lap top USB the sound should disappear as these power supplies are electrically quiet.
 
It is not a faulty Mojo as we can't stop the noise from the USB.
 
Rob

 

[headwhacker]

  The mechanical buzz is due to the USB charger being noisy. This noise modulates the PSU inductors, which creates the noise. The level of mechanical noise depends upon the PSU. If you use a lap top USB the sound should disappear as these power supplies are electrically quiet.
 
It is not a faulty Mojo as we can't stop the noise from the USB.
 
Rob

 
Hi Rob thanks for chiming in. The unit I had has the buzzing noise on different power sources. Be it Laptop USB, powerbank, iPad power brick and a power strip with built-in USB socket. Then the 2nd Mojo was totally quiet on all the same power sources.

 

[davidmolliere]

Quick question, I have a puzzling issue with the Mojo... I tried to use the micro usb to micro usb cable I had stocked with the FiiO E18 and it doesn't work (tried it with my phone and E18 and it works so it's not the cable). Any specific requirement for the Mojo I wouldn't be aware of? Before I order the cable for ZX2 (walkman to micro-usb)...
 
I know it's not my phone as @georgelai57 reported that it does work with the Huawei G8. Also it does work flawlessly with a simple USB to micro USB cable from my Mac. I checked with my Galaxy Tab S just in case and it doesn't work either... Ordered a high grade OTG micro to micro, hope there is no issue with the unit.
 
Puzzling...
Mojo + Computer with standard micro B to A = works
FiiO E18 + micro B to micro B + G8 = works
Mojo + micro B to micro B + G8 = doesn't work
Mojo + micro B to micro B + Galaxy Tab S = doesn't work
 
I don't get it...
 
 
Edit : So I went out to the store and purchased a simple USB A female to micro B OTG male and it works flawlessly. That will do until I get a proper adapter that does work. I still don't get why the other is not working...
 
I ordered a nice one from Forza Audio Works, I hope this works given the premium price,
 

 

[mscott58]

 
Thanks x RELIC x. Truly an astonishing DAC. I'm going to go back to some trance now. See you when The Claw sucks my batteries dry.

Great article! Well done and very informative (and matches my personal experience with the Mojo). 
 
Per the question someone had about the CDM and the Mojo, it's a bit of overkill, but the Mojo plugged into the CDM is a great blending of what's best about both. 

Cheers 

 

[Ike1985]

When charging, the sound I hear isn't from the headphone output, but from the device. Put your ear up to it whilst charging. Does it buzz or whine as in the SoundCloud recording earlier in this thread?

I already put my ear to it many times, never makes a sound ever.

 

[stevemiddie]

I already put my ear to it many times, never makes a sound ever.

Same here and I've got one of the very early ones 

 

[iceman16221]

  Same here and I've got one of the very early ones 

Mine also makes no noise, although I just got mine two weeks ago.

 

[Torq]

  The mechanical buzz is due to the USB charger being noisy. This noise modulates the PSU inductors, which creates the noise. The level of mechanical noise depends upon the PSU. If you use a lap top USB the sound should disappear as these power supplies are electrically quiet.
 
It is not a faulty Mojo as we can't stop the noise from the USB.
 
Rob

 
Mine does this ... sounds exactly like the kind of coil-whine I would get on some video cards under changing load and, oddly enough, when accessing an SSD on work laptop.  Doesn't seem to matter what the power source is though - can be an iPad charger, or my rMB running on its battery, or just a dedicated battery pack, and it's pretty much consistently present.
 
It doesn't bother me since I figured that's what it was, and it doesn't intrude on my listening at all (definitely just the mechanical noise), but its good to know for sure!

 

[GreenBow]

Is the charging noise loud enough to disturb music if you were listening quietly with open back headphones, while charging.

 

[Torq]

  Is the charging noise loud enough to disturb music if you were listening quietly with open back headphones, while charging.

 
Oh no ... it's extremely quiet, as in barely audible.
 
Sometimes, in a totally silent room I can hear it from a few feet away, but just putting my headphones (open back) on with nothing playing is more than enough to make it completely inaudible.
 
Otherwise I have to literally put the unit to my ear to hear it ... and it's still quiet.

 

[GreenBow]

Thank you torq,
I'd not even considered this could be a problem. Earlier on the thread I thought I understood that noises or vibration while charging meant sending it to Chord. There was were four possible effects when charging; hissing, whining, humming, or vibrating. I thought it was a regulator that caused it and could be fixed.

 

[viper2377]

Was listening to my mojo, took a break and charged it...came back powered on and everything lit up correctly... Then power light went out and volume buttons remained on... No output. Any ideas?? Nothing changed literally.....

 

[stevemiddie]

Was listening to my mojo, took a break and charged it...came back powered on and everything lit up correctly... Then power light went out and volume buttons remained on... No output. Any ideas?? Nothing changed literally.....

 
Mine does that if it is not connected to a source correctly. Try another source or cable maybe? 

 

[Torq]

  Thank you torq,
I'd not even considered this could be a problem. Earlier on the thread I thought I understood that noises or vibration while charging meant sending it to Chord. There was were four effects; hissing, whining,humming, or vibrating. I thought it was a rugulator that caused it and could be fixed.

 
It's not a problem ... and it's nice to have Rob confirm that.
 
I get hiss on my Mojo with my SE846 (which is normal, if not necessarily audible to everyone, per Rob Watts post here) and Etymotic HF2, but not with anything else I've tried it with.  And that hiss is so low in level that it's a non-issue for me.  Its so low level, in fact, that If I turn the Mojo on before I put the IEMs in my ears then it often takes several seconds for it to register.  In real terms, even with short silent passages in music, I don't hear it at all (long silent passages it's there if I am paying attention to it).
 
It's a fantastic little device.

 

[GreenBow]

   
It's not a problem ... and it's nice to have Rob confirm that.
 
I get hiss on my Mojo with my SE846 (which is normal, if not necessarily audible to everyone, per Rob Watts post here) and Etymotic HF2, but not with anything else I've tried it with.  And that hiss is so low in level that it's a non-issue for me.  Its so low level, in fact, that If I turn the Mojo on before I put the IEMs in my ears then it often takes several seconds for it to register.  In real terms, even with short silent passages in music, I don't hear it at all (long silent passages it's there if I am paying attention to it).
 
It's a fantastic little device.

I'm actually confused by what Rob Watts has written. It appears to contradict what John Franks 'Mojo Ideas' wrote in post 3858 on page 258. http://www.head-fi.org/t/784602/chord-mojo-the-official-thread-read-the-first-post-for-updated-info/3855
Quote, "Hello sorry for not posting sooner Yes we've shipped many thousands of units and we have had a very few well under ten with this problem it's due to a regulator issue on some early units. Naturally we soon altered the process and have solved this issue but there are a few out there please take it in for an immediate replacement. John E. Franks."
 
I was confident that if a Mojo was noisy when charging it could be sent for repair. I thought it would be kinder for me as a customer  to simply send it to Chord. Rather than return it to the retailer and have them ship it back to Chord. (If you know what I mean.)