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

[Torq]

   
Mojo in general may not be the problem, but I'm not convinced that my particular unit doesn't have an issue.
 
I literally have the fastest Macs it is possible to buy today.  Other's are having it work fine with MUCH slower hardware with far fewer resources.  The ONLY common factor with this issue is the DAC.  So either my DAC has an issue or there's something common to my computers that I don't know about (one of them, a fully-specced Retina Mac Book Pro was brand new as of yesterday - so there's no third party software in the way).
 
I avoid JRiver for a variety of reasons - however I included it in my testing as an attempt to eliminate Audirvana as a possible cause.  The issue exists with Roon also, so it's not the playback software.  And it's definitely not the performance of the computer.

So, after lots more trouble-shooting, I've eliminated my Mojo as the cause of the issue.  It's reproducible on at least one other DSD DAC - though dropouts are more frequent with the Mojo for some reason.
 
About the only thing left to try is play via Windows and a Mac running a pre-El Capitan build of OS X.
 
I've used five separate Macs, all MORE than powerful enough to handle the "load" (even on my slowest machine we're talking single digit percentage CPU usage).  Half a dozen USB cables including Amazon Basics, Monoprice, Anker, AudioQuest Cinnamon etc.  It happens with Audirvana+, Roon, HQPlayer, and JRiver.  It's more common on higher bit-rate files (up to quad-rate/DSD256), but still happens at DSD128 - not seen it at DSD64 (1x) yet.  It'll play all day at 32/352 or 32/384KHz mode (identical data rate to DSD256) ... but put it in DoP mode and the dropouts begin.  It happens with all of my native DSD music files.  It happens with Redbook audio up sampled to DSD (so not just native files).  It happens with native USB 2.0 and 3.0 ports.
 
At best I can fathom now is that it's a timing issue with data in DoP format (or DoP is less tolerant of timing issues than simple PCM - even though the container is the same).  No idea what is causing the timing glitch.  Maybe it's an El Capitan issue.
 
Won't post on it again in this thread unless I can resolve it.  But did want to confirm that it was not down to a fault on my Mojo.

 

[harpo1]

Just got mine in a trade for my LCD2, this thing is glorious, I have listened to it through my iPhone with Tidal, using either my Audeze Sine or my Noble K10u, really beautiful, soundstage presence detail, bass, hard to describe how good this is. When I listen to it more, I'll leave more impressions. However, does any one know if the Pono can be connected to this with a simple interconnect in single ended mode (I know it can't be connected in balanced mode). Thanks.

Mojo only has digital inputs.  I don't own a Pono but if it has a coax out or optical out you can hook it up that way.

 

[paruchuribros]

Is there any portable player have a sound quality of chord mojo? I do not want to carry 2 things other than phone (don't want to use phone for the music since music play drains the battery).

 

[x RELIC x]

Just got mine in a trade for my LCD2, this thing is glorious, I have listened to it through my iPhone with Tidal, using either my Audeze Sine or my Noble K10u, really beautiful, soundstage presence detail, bass, hard to describe how good this is. When I listen to it more, I'll leave more impressions. However, does any one know if the Pono can be connected to this with a simple interconnect in single ended mode (I know it can't be connected in balanced mode). Thanks.

No go with the Pono.

Digital input only with the Mojo.

I'm a poet!

 

[x RELIC x]

Is there any portable player have a sound quality of chord mojo? I do not want to carry 2 things other than phone (don't want to use phone for the music since music play drains the battery).

That's a loaded question!! Some will say yes, emphatically. Some will say no, emphatically.

It would help to understand the different approach Chord takes to the Digital to Analogue Conversion in their DACs and how the analogue output is implemented with very little noise. Also, look at the fantastic measurements of the Mojo compared to pretty much every other portable player and many desktop solutions. Then go and audition one and compare to other devices you may be interested in (optimally).

The third post has most of the information about what makes Mojo technically special from the designer of the DAC himself. I suggest start reading the third post quotes from Rob Watts first to gather a baseline for what the Mojo can do. Second, there are 26 reviews for the Mojo currently on Head Fi.

 

[brent75]

I bought the Audioquest Jitterbug when I bought the Dragonfly Red. If I end up keeping the Mojo over Red, will the Jitterbug be useless/redundant to the Mojo...or should I keep it?
 
(I think I'll get about $45 back or so if I return)

 

[x RELIC x]

I bought the Audioquest Jitterbug when I bought the Dragonfly Red. If I end up keeping the Mojo over Red, will the Jitterbug be useless/redundant to the Mojo...or should I keep it?

(I think I'll get about $45 back or so if I return)

Redundant. Because of the way Rob's DACs work he says they are all immune to jitter, this includes the Mojo. Some have purchased the Jitterbug with the Mojo and have reported no change in sound. Best to test for yourself if you have one.

Edit: This is copied from (of course) the third post in this thread. There is SO MUCH info there people.

Originally Posted by Rob Watts View Post

Quote:
Originally Posted by Skyyyeman View Post

Clock jitter -- What is clock jitter? The reason I ask is that in considering different DAPs to use as transports to output a digital signal to the Mojo, I've seen some varying specs for clock jitter on different DAPs, as follows:

AK100 90 ps (pico seconds)
AK120 50 "
AK240 50 "

Question: Does clock jitter degrade the digital signal before it's send out from the DAP? Or are they referring to clock jitter of the internal dac, in which case clock jitter doesn't matter since the signal never reaches the dac (it's been output beforehand)?

If clock jitter degrades the signal before it's sent out, then it appears that the AK100 is not as good a transport as the other two. But would the difference be discernible?

Thx

Clock jitter is timing uncertainty (or inaccuracy) on the main clock that is feeding the digital outputs. Its often expressed as cycle to cycle jitter as an RMS figure, but can be total jitter which includes low frequency jitter too. Total jitter is the most important specification. If you want here is a good definition:

https://en.wikipedia.org/wiki/Jitter

As you can see, the jitter subject can get complicated and its often abused by marketing...

But with all of my DAC's you do not need to worry at all about source jitter, so all of the above AK numbers are fine. So long as its below 2uS (that is 2,000,000 pS) you are OK, and nobody has jitter that bad!

Rob

Quote:
Originally Posted by Rob Watts View Post

The reasons why sources and digital interconnects sound different are well understood - see some of my posts. In a nutshell it is not jitter (all my DACs are completely immune to source jitter) but down to RF noise and distorted currents from the source flowing into the DAC's ground plane. The RF noise inter-modulates with the analogue electronics, creating random noise as a by product, which creates noise floor modulation, and that makes it sound brighter or harder. The correlated or distorted currents very subtly add or subtract to small signals, thus changing the fundamental linearity, which in turn mucks up depth perception.

But I also agree in that lots of people hear changes that are not there - I for one have never heard any difference with optical cables (assuming all are bit perfect) with my DAC's, but lots of folks claim big differences. Placebo, or listening with your wallet, plays a part here. Then there are cases of people preferring more distortion... Listening tests must be done in a very controlled and careful fashion, particularly if you are trying to design and develop things.

Rob

 

[x RELIC x]

Spoiler: Warning: Spoiler!

So, after lots more trouble-shooting, I've eliminated my Mojo as the cause of the issue.  It's reproducible on at least one other DSD DAC - though dropouts are more frequent with the Mojo for some reason.

About the only thing left to try is play via Windows and a Mac running a pre-El Capitan build of OS X.

I've used five separate Macs, all MORE than powerful enough to handle the "load" (even on my slowest machine we're talking single digit percentage CPU usage).  Half a dozen USB cables including Amazon Basics, Monoprice, Anker, AudioQuest Cinnamon etc.  It happens with Audirvana+, Roon, HQPlayer, and JRiver.  It's more common on higher bit-rate files (up to quad-rate/DSD256), but still happens at DSD128 - not seen it at DSD64 (1x) yet.  It'll play all day at 32/352 or 32/384KHz mode (identical data rate to DSD256) ... but put it in DoP mode and the dropouts begin.  It happens with all of my native DSD music files.  It happens with Redbook audio up sampled to DSD (so not just native files).  It happens with native USB 2.0 and 3.0 ports.

At best I can fathom now is that it's a timing issue with data in DoP format (or DoP is less tolerant of timing issues than simple PCM - even though the container is the same).  No idea what is causing the timing glitch.  Maybe it's an El Capitan issue.

Won't post on it again in this thread unless I can resolve it.  But did want to confirm that it was not down to a fault on my Mojo.

Torq, I believe in the Nagra HD DAC thread they were also reporting drop outs with DSD from El Capitan.

 

[Torq]

 

Spoiler: Warning: Spoiler!

 

@Torq, I believe in the Nagra HD DAC thread they were also reporting drop outs with DSD from El Capitan.

Thanks!
 
It seems the drop outs being reported there are with the Chord DAVE ... and the Nagra HD DAC is working fine.  So there may be more to it than just OS X being a git.

 

[x RELIC x]

Thanks!

It seems the drop outs being reported there are with the Chord DAVE ... and the Nagra HD DAC is working fine.  So there may be more to it than just OS X being a git.

Yes, sorry, the DAVE mentioned in the Nagra thread. Curious though as I've also read around the web about El Capitan causing issues with other DACs as well. It's a wider issue than just your Mojo unit. I'm simply not a big fan of DSD so I really can't help much further than that. :redface:

 

[Torq]

Yes, sorry, the DAVE mentioned in the Nagra thread. Curious though as I've also read around the web about El Capitan causing issues with other DACs as well. It's a wider issue than just your Mojo unit. I'm simply not a big fan of DSD so I really can't help much further than that.

I greatly appreciate the pointer all the same!
 
It is curious that it's two Chord units ... wonder how similar the interface code is for those.
 
DoP is a hack at best, so it doesn't surprise me that it is a bit iffy.
 
All this started as I wanted to take a more serious look at DSD before deciding what DAC to buy for my 2nd "main" headphone system (i.e. another high-end one).  To date I've not heard anything that suggests it's anything but "different" to PCM (when I can tell a difference at all).  For sure, I've not heard everything.  Even comparing plain old Redbook to quad-rate DSD is not moving the needle in DSD's favor so far.  Not exactly the experience I expected given all the hype.

 

[x RELIC x]

I greatly appreciate the pointer all the same!

It is curious that it's two Chord units ... wonder how similar the interface code is for those.

DoP is a hack at best, so it doesn't surprise me that it is a bit iffy.

All this started as I wanted to take a more serious look at DSD before deciding what DAC to buy for my 2nd "main" headphone system (i.e. another high-end one).  To date I've not heard anything that suggests it's anything but "different" to PCM (when I can tell a difference at all).  For sure, I've not heard everything.  Even comparing plain old Redbook to quad-rate DSD is not moving the needle in DSD's favor so far.  Not exactly the experience I expected given all the hype.

I know a lot of DSD fans will disagree with this but I also don't find anything special about DSD. Actually DSD sounds more flat and wide to me, which sounds more fake (to me). The code in the Mojo is similar to DAVE, just nowhere near as robust. You simply can't fit that much code in to the Mojo's smaller FPGA. Mojo's WTA filter tap length is not disclosed but I would say it's not more than the Hugo at 26,000 taps. The WTA filter in DAVE is 164,000 taps running in parallel on 166 DSP cores in the FPGA. That's a lot of complex filtering going on!

 

[Torq]

I know a lot of DSD fans will disagree with this but I also don't find anything special about DSD. Actually DSD sounds more flat and wide to me, which sounds more fake (to me). The code in the Mojo is similar to DAVE, just nowhere near as robust. You simply can't fit that much code in to the Mojo's smaller FPGA. Mojo's WTA filter tap length is not disclosed but I would say it's not more than the Hugo at 26,000 taps. The WTA filter in DAVE is 164,000 taps running in parallel on 166 DSP cores in the FPGA. That's a lot of complex filtering going on!

I'd imagine there are large differences in many areas between the Mojo (or Hugo) and DAVE ... but it's the USB interface and the DoP unpacking that I'd be interested in relation to this DSD drop-out issue.  If that "code" is the same, then it would explain why both seem to be affected.  I could certainly see the implementations of those two elements of the solution being different also, just wondering if they actually are - or if the differences are limited to what comes after the data stream has been fully recovered.

 

[x RELIC x]

I'd imagine there are large differences in many areas between the Mojo (or Hugo) and DAVE ... but it's the USB interface and the DoP unpacking that I'd be interested in relation to this DSD drop-out issue.  If that "code" is the same, then it would explain why both seem to be affected.  I could certainly see the implementations of those two elements of the solution being different also, just wondering if they actually are - or if the differences are limited to what comes after the data stream has been fully recovered.

DAVE has a DSD+ mode that you can manually select when playing DSD. It has a more robust treatment of DSD, but I imagine the approach is largely similar.

 

[Torq]

For a laugh ... now up sampling to 32/768 KHz and feeding that to the Mojo ... absolutely rock solid ... even on my little Retina MacBook.  Nothing I do on the machine seems to give the audio any issues at all.  So whatever is causing my dropout issue is limited to DoP transfers (both for the Mojo and the ALO Audio International+ Optical Edition).