[GRUMPYOLDGUY]

Yarp, beat me to it. It's probably the cause. 

Mojo's very vulnerable to EMI/RFI down the USB, Chord themselves suggest that you put the phone in flight mode. Because that's kinda useless, I just use my old phone with it, which I can leave in flight mode without being incommunicado whenever I have the Mojo on. 

I must have a very unique Mojo... This is the second issue in this thread that you've mentioned that I've never experienced. That's not to say they don't exist, just that they haven't happened to me.

I use the Mojo plugged into a 2A charger regularly and it gets warm, but never to the point of thermal auto shutdown. Even when listening for hours on end. I also have never experienced RFI through the USB... I use a pretty short cable and keep my phone right next to the Mojo (sometimes on top of!)

 

[Ancipital]

I must have a very unique Mojo... This is the second issue in this thread that you've mentioned that I've never experienced. That's not to say they don't exist, just that they haven't happened to me.

I use the Mojo plugged into a 2A charger regularly and it gets warm, but never to the point of thermal auto shutdown. Even when listening for hours on end. I also have never experienced RFI through the USB... I use a pretty short cable and keep my phone right next to the Mojo (sometimes on top of!)

 
First off, long may it continue. I'm sure we'd much rather that you never had a problem 

 
Secondly, it's very situational. The noise is caused when you're plugged into a mobile phone, in a low/no signal area. As the phone cranks the gain of the cellular radio, you can hear the pulses as it tries to get back in contact with the cell. I'm lucky enough to have a daily commute where I'm on a train that goes down some pretty crazy urban canyons where this happens really frequently.
 
You can duplicate it yourself by plugging your Mojo into a phone, and sticking it in a small Faraday cage (you often sound like someone who might have one, or know how to improvise one). If you don't plug Mojo into a phone with the baseband chipset active, in a very poor reception area, you may never hear it. However, when you do, it can make listening difficult and unpleasant.
 
I also tried leaving the Mojo strapped to the phone, but plugged into a Wifi-only tablet over USB to check (which looked a little weird). No issues at all in the zero signal area, so it really looks like it's over the USB from the other end rather than through the chassis.
 
Chord's advice, if you do suffer this issue, is to reach for flight mode. I just use my old phone in flight mode as a slightly shonky DAP, which works out reasonably as a cheap and flexible option.

 

[GRUMPYOLDGUY]

First off, long may it continue. I'm sure we'd much rather that you never had a problem 

Secondly, it's very situational. The noise is caused when you're plugged into a mobile phone, in a low/no signal area. As the phone cranks the gain of the cellular radio, you can hear the pulses as it tries to get back in contact with the cell. I'm lucky enough to have a daily commute where I'm on a train that goes down some pretty crazy urban canyons where this happens really frequently.

You can duplicate it yourself by plugging your Mojo into a phone, and sticking it in a small Faraday cage (you often sound like someone who might have one, or know how to improvise one). If you don't plug Mojo into a phone with the baseband chipset active, in a very poor reception area, you may never hear it. However, when you do, it can make listening difficult and unpleasant.

I also tried leaving the Mojo strapped to the phone, but plugged into a Wifi-only tablet over USB to check (which looked a little weird). No issues at all in the zero signal area, so it really looks like it's over the USB rather than through the chassis.

Chord's advice, if you do suffer this issue, is to reach for flight mode. I just use my old phone in flight mode as a slightly shonky DAP, which works out reasonably as a cheap and flexible option.

Sounds like a fun weekend experiment.

Incidentally I have seen RFI picked up by my (powered off) Continental V5 ride into the Mojo on the interconnect and leak into the adjacent channel on the Mojo where my IEMs were plugged in at the time.

 

[Soundizer]

There seems to be significant noise related issues with Mojo. Although I do not think I could hear noise when used from my Apple iMac I decided just in case to purchase:
(Audioquest Jitterbug) + (Audioquest micro usb cable that minimises noise).

It made a big difference and the audio sounds very pure and constant. Why does it sound so much better- i do not know. However Chord Technical Support did confirm the Mojo Could sound better with the Jiiterbug, but did not detail the reasons why.

DESKTOP SET UP:
I think the Mojo is fantastic as a desktop solution- Because desk space can be a premium and you can simply power it from the Computer so fewer bulky plugs required.

 

[vapman]

There seems to be significant noise related issues with Mojo. Although I do not think I could hear noise when used from my Apple iMac I decided just in case to purchase:
(Audioquest Jitterbug) + (Audioquest micro usb cable that minimises noise).

It made a big difference and the audio sounds very pure and constant. Why does it sound so much better- i do not know. However Chord Technical Support did confirm the Mojo Could sound better with the Jiiterbug, but did not detail the reasons why.

DESKTOP SET UP:
I think the Mojo is fantastic as a desktop solution- Because desk space can be a premium and you can simply power it from the Computer so fewer bulky plugs required.

They did say why, they also said it works just as well as a (much cheaper) microUSB cable with ferrite cores!

 

[Mython]

Not Mojo-specific, but obviously of related interest:  http://www.youtube.com/watch?v=vFZWQbHXwuI

 

[Ancipital]

Sounds like a fun weekend experiment.

Incidentally I have seen RFI picked up by my (powered off) Continental V5 ride into the Mojo on the interconnect and leak into the adjacent channel on the Mojo where my IEMs were plugged in at the time.

 
Ohhh, slight threadjack, but tell me about the V5. I've always been curious about those (though maybe I should be strong, can't carry a phone+Mojo+V5 stack in my pocket in commuter rush).

 

[Soundizer]

They did say why, they also said it works just as well as a (much cheaper) microUSB cable with ferrite cores!
[/quote]


Ok I was not aware. However I should have explained that my input from Chord Technical was directly from Chord Technical.

Here is a copy and paste of the email to me from Chord UK Engineer:
"We do put a lot of attention into removing Jitter, as we reclock everything that comes into our DACs. But Rob Watts, the guy who designs this technology does believe that the Jitter Bug does make it sound better!"


PS. On a totally irrelevant point but interesting - the designer of the Audioquest Nighthawks Headphone uses the Mojo to listen to then, over any other Dac/Amp including the Audioquest Red Dragon Fly.

 

[god-bluff]

If anyone is looking for a nice quality velvet bag for their Mojo I recommend buying a pair if Musical Fidelity EB33s for 20 odd quid. perfect fit. Throw or give the esrphones away. They're pretty rubbish.

 

[Soundizer]

Not Mojo-specific, but obviously of related interest:  http://www.youtube.com/watch?v=vFZWQbHXwuI

Awesome video

 

[GRUMPYOLDGUY]

They did say why, they also said it works just as well as a (much cheaper) microUSB cable with ferrite cores!

Ok I was not aware. However I should have explained that my input from Chord Technical was directly from Chord Technical.

Here is a copy and paste of the email to me from Chord UK Engineer:
"We do put a lot of attention into removing Jitter, as we reclock everything that comes into our DACs. But Rob Watts, the guy who designs this technology does believe that the Jitter Bug does make it sound better!"


PS. On a totally irrelevant point but interesting - the designer of the Audioquest Nighthawks Headphone uses the Mojo to listen to then, over any other Dac/Amp including the Audioquest Red Dragon Fly.[/quote]

I tried getting some lab measurements from AQ on the jitterbug to get them to prove it does what they say it does. They ended up CCing about 5 people on the email and it came down to "just try it". Jitterbug is a garbage product from a snake oil company in my mind.

 

[vapman]

I believe it was actually rob who posted here to say a ferrite cable does the same job as a jitterbug.

 

[GRUMPYOLDGUY]

Ohhh, slight threadjack, but tell me about the V5. I've always been curious about those (though maybe I should be strong, can't carry a phone+Mojo+V5 stack in my pocket in commuter rush).

I have mixed feelings about it. The sensitivity to RFI is insane and the noise floor is pretty high... But if I put my phone in HSPA+ mode instead of LTE (different frequency band) the RFI isn't a problem and noise isn't terribly distracting with music playing. I really like the sound though. I don't have measurements to back it up, so I don't want to speculate... But it's my favorite sounding amp. I consider it more transportable than portable though... It's very microphonic, so not sure I'd try carrying it in my pocket.

 

[GRUMPYOLDGUY]

I gues you disagree with Robb Watts then with your crude statement of an entire Company. Or maybe you are Grumpy.

Yeah, when a company tells me I have to buy their product to see what it does... That's where I draw the line.

I don't argue there aren't substantial advantages to passive filtering on USB lines... Particularly on the voltage lines for devices that are powered that way. But a ferrite bead is a cheaper way to eliminate RFI being carried in on the USB in other cases... Filtering noise on the data lines has little benefit to data integrity, the differential signalling is already very robust. Main benefit is preventing high frequency noise from leaking into the analog path.

 

[daberti]

  How exactly does the USB adapter block make it easier to use the Mojo with the Apple Lightning to USB Camera Adapter? 

You lucky: I cannot get my own CCK connected to Mojo with Mojo CAP