Chord Mojo(1) DAC-amp ☆★►FAQ in 3rd post!◄★☆

[headmanPL]

I am getting glitching on UAPP as well, never had it before recently. I assumed it was a mojo problem. Guess I will try with another dac.

UAPP has had several updates recently. I have kept the app updated on my Xperia Z3 and haven't experienced these glitches. I wonder if that's true of all mobiles?

 

[Blasyrkh]

I am getting glitching on UAPP as well, never had it before recently. I assumed it was a mojo problem. Guess I will try with another dac.

it's "nice" to hear... What type of glitching? Could you test onkyo hf?

I assume the problem should be addressed to clock synching with asynchronous USB.
Dac1 (8 years old dac with synch USB! ) works flawlessly. E18 works too, and maybe that's synch too.

With uapp tweak1 activated, the speed problem is solved, and that tweak deactivates the USB clock of the device.

Maybe mython was right it's a phone problem, but chord should have thinked about these kinds of problems.there are too many compatibility issues

 

[fluidz]

I sent Chord an email the other day

"Hi

I've run into a bit of bad luck with two Mojo's.
First unit I ordered from Amazon produced a Squeal whilst charging. Sent it back.

I received another unit and it hisses whilst charging, the volume of the hiss depends on the charger/usb port used. I use the included charging cable. Chargers - Apple 1a, Apple 2.5a, Usb 2/3 ports on Pc. These chargers produce no noise with other devices.

It only makes a loud hissing noise if the unit is turned off and charging. When the Mojo is simultaneously turned on and charging the noise is barely audible unless I put my hear next to the unit.

I believe this is yet another bad Mojo. Whats the chance of me receiving another bad unit? I've a bad feeling a lot of the Mojos have issues with power.

Serial numbers :

First Mojo (returned) : S/N MO23869
Current Mojo : S/N MO31325"

This was their reply :

"Hello,

The hissing that you're experiencing is completely normal and there's nothing to worry about. The units that you have received are not bad.

The noise that you are experiencing is the high powered charging circuit kicking in to effectively charge the battery. The reason as to why this may not occur when the unit is operational due to the low power charging circuit being active.

Best,

Edd Harris - Marketing Manager"

What I find odd is Edd is saying its normal yet most People claim they don't hear a hiss/whine, and it's not mentioned in the manual

 

[Mython]

  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. 
 
Charging times - its 4 to 5 hours if the unit is off from flashing red to full charge. But if you are using it at the same time, it will take much longer (maybe 12 hours), as current is being drawn to feed Mojo and less to charge the battery. Check that the charging LED is not flashing, as this indicates a fault such as insufficient current from the PSU.
 
Rob

 

[enthusiast]

I guess that's why some summit-fi stationary Amp/Dac manufacturer went built-in batteries.

 

[audionewbi]

Can someone guess what this guy is doing? He is a famous analog cable designer in Japan I just do not get what he is doing?!

 

[Mython]

  Can someone guess what this guy is doing? He is a famous analog cable designer in Japan I just do not get what he is doing?!

 
 
Simple: he is invalidating his Mojo warranty.
 
Anything else I can help you with?

 

[stevemiddie]

  Can someone guess what this guy is doing? He is a famous analog cable designer in Japan I just do not get what he is doing?!

 
He's moving screws around.    
 
Perhaps your question should be 'why is he doing that?' 

 

[audionewbi]

   
 
Simple: he is invalidating his Mojo warranty.
 
Anything else I can help you with?

 
 

   
He's moving screws around.    
 
Perhaps your question should be 'why is he doing that?' 

I guess the moral of the story is if we dont all quiet now we might end up like him, I swear I think once we reach a certain level that we know there isn't anything else to mod/buy we will do random thing just for the heck of it
Now time for me to do the "screw mod".....

 

[NaiveSound]

If mojo Was balanced how would the sound differ?

 

[audionewbi]

If mojo Was balanced how would the sound differ?

The entire idea of balance, beside power, is to improve channel separation which Mojo already aces. I think the entire movement of portable balance for IEM has wrongly been exploded. Trust me i got sucked into it but in truth there is very little achieved, specially now considering how there is no standard on balance termination. As an end user we just cannot buy one balance cable that can cover all the balance design in the market, the end result is just messy collection of expensive cables with no final audible improvements. 

 

[Mython]

If mojo Was balanced how would the sound differ?

 
Here are a couple of relevant quotes (from different threads) regarding the pros and cons of balanced output stage circuit design. Bear in mind that these were written by the designer of Mojo, himself:
 
 
 

  Component count is very important for transparency. Doubling the number of parts in the direct signal path does degrade depth perception and detail resolution.
 
But there is another problem with balanced operation. Imagine a balanced differential in, differential out amplifier. The input stage is normally a differential pair (maybe cascoded) with a constant current source. Now the input stage is free to move up and down to accommodate the common mode voltage - but the input stage common mode impedance is non linear, and if the common mode voltage has a signal component (it always will have due to component tolerances) then this will create a signal dependent error current, thereby generating distortion. Unfortunately, the negative feedback loop of the amplifier can't correct for this distortion as it can't see the error on the summing nodes. So there will always be a limit to the performance. With SE operation, this problem does not occur, as the differential input stage is clamped to ground.
 
Now DAC designers are well aware of this - that's why all high performance DAC's use two single ended I to V converters from the current OP of the DAC's, then use a differential to SE converter to create the voltage OP. There are other reasons for doing this as well, as the DAC requires a very low impedance virtual ground for low distortion, and you can only get this using dual SE amps - another problem is RF and its much easier to decouple SE than differentially - this in turn creates a lot more noise floor modulation, making it sound less smooth.
 
But for me the most important is transparency. I had an amp that had two modes - differential or SE - listening in balanced mode flattened the sound stage depth dramatically,and it sounded harder, less smooth. That said, there are circumstances when balanced operation can be better than SE, for example when you are looking at connecting a pre-amp to a power amp, and what is best depends upon particular circumstances. In short, if SE operation is noisy, try balanced.
 
Rob 

 
 

 

  Rob you should give a definitive 'why SE is better' explanation. Get it over with, because many (most) audiophiles have been biased towards balanced and are not going to understand where you are coming from.
 
One good argument I heard from the Densen founder (Thomas Sillesen) is that each half of the signwave runs through a series of components that will always have tolerances different from each other, so when combining the signal they will not ever match, causing an increase in distortion (of some kind I cannot remember).
 
Charles Hanson, of Ayre, who is a proponent of fully balanced equipment, has even stated that for pure sound quality SE will always sound better, but this is on the bench, where the power supply and analog signal stages can be kept physically apart. When putting them in a box he prefers balanced.

Well this is a complex subject, and sometimes a balanced connection does sound better than single ended (SE) - in a pre-power context - but it depends upon the environment, and the pre and power and the interconnect. But the downside of balanced is that you are doubling the number of analogue components in the direct signal path, and this degrades transparency. In my experience every passive component is audible, every metal to metal interface (including solder joints - I once had a lot of fun listening to solder) has an impact - in case of metal/metal interfaces it degrades detail resolution and the perception of depth. So going balanced will have a cost in transparency.
 
In DAC design, going balanced is essential with silicon design; there is simply too much substrate noise and other effects not too. But with discrete DAC's you do not need to worry about this, so going SE on a discrete DAC is possible, and is how all my DAC's are done. But differential operation hides certain problems (notably reference circuit) that has serious SQ effects; so going SE means those problems are exposed, which forces one to solve the issue fundamentally. In short, to make SE work you have to solve many more problems, but the result of solving those problems solves SQ issues than differential operation hides when you do measurements.
 
In the case of Dave, I have gotten state of the art measured performance - distortion harmonics below -150 dB, zero measurable noise floor modulation - and there is no way you could do this with a differential architecture. So it is possible to have better measured performance with SE than differential, but it is a lot harder to do it - indeed, the only way of getting virtually zero distortion and noise floor modulation is SE.  
 
Rob 

 

[x RELIC x]

What Rob said... :wink_face:

TL;DR

With off the shelf DACs it's easier to correct/mask the issues with balanced output than to correct the issues at the DAC. With the Chord's discrete DAC implementations it's cleaner and more transparent SE out as more components at this level adds distortion.

 

[georgelai57]

What Rob said...

TL;DR

With off the shelf DACs it's easier to correct/mask the issues with balanced output than to correct the issues at the DAC. With the Chord's discrete DAC implementations it's cleaner and more transparent SE out as more components at this level adds distortion.

IDR (I did read) but thanks for the TL;DR which summed it for the layman.

 

[NaiveSound]

But is balanced iems cables and anything else sonically different than regular? I guess I just don't understand in layman's tears what balanced is