[adeseaso]

So...

If Chord DACs don't care about input jitter as per the FAQ, where does that leave us with source selection?

Is a low jitter source like the Allo Digione a bad investment? Is a simple USB to optical adapter out of the iMac all you need since it eliminates RF noise?

I'd love to hear some opinions on this before getting a source for my newly acquired Hugo and Mojo that I'll use with HD600s by the computer. I think the Mojo + HD600 in particular is a fantastic combo. No fatigue, just mid range resolution for days with velvety detailed top. It's the first DAC + headphone combo I've tried that reminds my of my old Harbeth P3ESRs that I sadly had to let go of.

 

[miketlse]

So...

If Chord DACs don't care about input jitter as per the FAQ, where does that leave us with source selection?

Is a low jitter source like the Allo Digione a bad investment? Is a simple USB to optical adapter out of the iMac all you need since it eliminates RF noise?

I'd love to hear some opinions on this before getting a source for my newly acquired Hugo and Mojo that I'll use with HD600s by the computer. I think the Mojo + HD600 in particular is a fantastic combo. No fatigue, just mid range resolution for days with velvety detailed top. It's the first DAC + headphone combo I've tried that reminds my of my old Harbeth P3ESRs that I sadly had to let go of.

Yes the Chord dacs are immune to jitter, but source selection is still important. Let me explain.

Like most of the early Mojo owners, I started with a phone as the music source.
Phones do generate RFI, and Apple phones are regarded as among the worst offenders. RFI causes crackles etc, plus the low level electrical noise (this can be RFI and/or electrical noise generated internally by a phone/computer/etc) tends to make music sound 'brighter' - using optical removes the RFI, but the result is that music can sound less bright. Some people prefer that slight brightness using USB - it is all down to personal preferences.

I started with the Samsung Galaxy Note 3, plus UAPP music player, plus a ferrite choke, to remove virtually all the RFI crackles, but the music still felt brighter than when using optical.
I then changed to use a Shanling M1 for the music transport (no phone signal pollution), and that faint brightness to the music had gone. Now USB from the M1 and optical from my computer sound the same, for both the Mojo and Hugo 2. I did not return to using a phone.

For recordings of choral music sung in a church:

• Optical provided the sensation of listening to a very clear recording of the music performance
• USB with the faint brightness, provided the sensation of being present at the actual live music performance.

So yes it is possible to hear subtle differences between the different inputs.
Most of my listening is using optical input, but optical has the downside that one is limited to 192 music.
If one wants to use higher res music, one needs usb or coaxial input - but the choice of a low noise input source becomes important.

For desktop use:

• the Allo Digione can still be a good investment for optical.
• the Allo Usb-bridge has a good reputation as a low noise usb source
• This dap has been getting good writeups as an optical source for the MScaler

For mobile use:

• there is always the Chord Poly

 

[paruchuribros]

Yes the Chord dacs are immune to jitter, but source selection is still important. Let me explain.


Like most of the early Mojo owners, I started with a phone as the music source.

Phones do generate RFI, and Apple phones are regarded as among the worst offenders. RFI causes crackles etc, plus the low level electrical noise (this can be RFI and/or electrical noise generated internally by a phone/computer/etc) tends to make music sound 'brighter' - using optical removes the RFI, but the result is that music can sound less bright. Some people prefer that slight brightness using USB - it is all down to personal preferences.


I started with the Samsung Galaxy Note 3, plus UAPP music player, plus a ferrite choke, to remove virtually all the RFI crackles, but the music still felt brighter than when using optical.

I then changed to use a Shanling M1 for the music transport (no phone signal pollution), and that faint brightness to the music had gone. Now USB from the M1 and optical from my computer sound the same, for both the Mojo and Hugo 2. I did not return to using a phone.


For recordings of choral music sung in a church:

• Optical provided the sensation of listening to a very clear recording of the music performance
• USB with the faint brightness, provided the sensation of being present at the actual live music performance.

So yes it is possible to hear subtle differences between the different inputs.

Most of my listening is using optical input, but optical has the downside that one is limited to 192 music.

If one wants to use higher res music, one needs usb or coaxial input - but the choice of a low noise input source becomes important.


For desktop use:

• the Allo Digione can still be a good investment for optical.
• the Allo Usb-bridge has a good reputation as a low noise usb source
• This dap has been getting good writeups as an optical source for the MScaler

For mobile use:

• there is always the Chord Poly

Poly is too rich for me.


So, I have got Hiby R3 with Shanling L2 Type-C to Micro USB Audio Cable and Chord Mojo. That is a perfect combo. No Jitter or cracking noise with Shanling L2 cable. I highly advice to buy this cable.

 

[Pentagonal]

I own a Mojo and think it's amazing and a marvel. That said, I have found it does sound different with different hardware and software sources over optical. I believe that Mr. Watts is right that his code internally retrieves and recreates the signal perfectly, however in practice the FPGA hardware may be introducing its own noise and timing distortion as it works harder to recover sources with higher levels of jitter. From what I've read by Ted Smith, the PS Audio DirectStream DAC engineer (which has also has FPGA jitter elimination), he believes that the FPGA has to work harder to decode sources with higher jitter which causes power supply modulation and degrades output clock accuracy. (Also to note, he has released firmware updates to make the entire DAC sound better by improving the code. Rob and Ted are apparently on first name basis, too!)

Uptone engineer John Swenson in the quote linked below claims digital phase noise has a "fingerprint" which can pass through optical isolation by being recreated in the buffer and reclocker itself. My Mojo clearly sounds different when A/B switching two internal clock sources for my Mac's single optical out (create an Aggregate device and try switching clock sources for yourself), switching between 16 bit output vs 24 bit output of the same 16/44.1 file, playing the same files using different playback software, using a high-jitter Google Chromecast optical out, and between my three different computer optical interfaces. I believe it's all to do with electrical noise and timing distortion created inside the FPGA as it does different kinds of processing. The Mojo is amazing, but my experience has shown me that it can only sound its best with a clean input.

From: https://audiophilestyle.com/forums/topic/55217-sonore-opticalrendu/page/30/#comments

Clock phase noise


Phase noise is a frequency measurement of "jitter", yes that term that is so completely mis-understood in audio circles that I'm not going to use it. Phase noise is a way to look at the frequency spectrum of jitter, the reason to use it is that there seems to be fairly decent correlation to sound quality. Note this has nothing to do with "pico seconds" or "femto seconds". Forget those terms, they do not directly have meaning in audio, what matters is the phase noise. Ynfortunately phase noise is shown on a graph, not a single number, so it is much harder to directly compare units. This subject is HUGE and I'm not going to go into any more detail here.


Different oscillators (the infamous "clocks" that get talked about) can have radically different phase noise. The level of phase noise that is very good for digital audio is very difficult to achieve and costs money. The corollary is that the cheap clocks used in most computer equipment (including network equipment) produce phase noise that is very bad for digital audio.


The important thing to understand is that ALL digital signals carry the "fingerprint" of the clock used to produce them. When a signal coming from a box with cheap clocks comes into a box (via Ethernet or USB etc) with a much better clock, the higher level of phase noise carried on the data signal can contaminate the phase noise of the "good" clock in the second box. Exactly how this happens is complicated, I've written about this in detail if you want to look it up and see what is going on.


The contamination is not complete, every time the signal gets "reclocked" by a much better clock the resulting signal carries an attenuated version of the first clock layered on top of the fingerprint of the second clock. The word "reclocked" just means the signal is regenerated by a circuit fed a different clock. It may be a better or a worse clock, reclocking doesn't always make things better!


As an example if you start with an Ethernet signal coming out of a cheap switch, the clock fingerprint is going to be pretty bad. If this goes into a circuit with a VERY good clock, the signal coming out contains a reduced fingerprint from the first clock layered on top of the good clock. If you feed THIS signal into another circuit with a very good clock, the fingerprint from the original clock gets reduced even further. But if you feed this signal into a box with a bad clock, you are back to a signal with a bad fingerprint.

...

The summary is that stringing together devices with GOOD clocking can dramatically attenuate the results of an upstream bad clock.


I hope this gives a little clarity to the situation.



John S.

 

[adeseaso]

Thanks guys, i decided to keep the mojo mobile and went for the Xduoo X10T II. Looking forward to trying it out.

 

[miketlse]

Thanks guys, i decided to keep the mojo mobile and went for the Xduoo X10T II. Looking forward to trying it out.

It does look like an interesting piece of kit, so your feedback will be interesting to posters.

 

[Deftone]

I own a Mojo and think it's amazing and a marvel. That said, I have found it does sound different with different hardware and software sources over optical. I believe that Mr. Watts is right that his code internally retrieves and recreates the signal perfectly, however in practice the FPGA hardware may be introducing its own noise and timing distortion as it works harder to recover sources with higher levels of jitter. From what I've read by Ted Smith, the PS Audio DirectStream DAC engineer (which has also has FPGA jitter elimination), he believes that the FPGA has to work harder to decode sources with higher jitter which causes power supply modulation and degrades output clock accuracy. (Also to note, he has released firmware updates to make the entire DAC sound better by improving the code. Rob and Ted are apparently on first name basis, too!)

Uptone engineer John Swenson in the quote linked below claims digital phase noise has a "fingerprint" which can pass through optical isolation by being recreated in the buffer and reclocker itself. My Mojo clearly sounds different when A/B switching two internal clock sources for my Mac's single optical out (create an Aggregate device and try switching clock sources for yourself), switching between 16 bit output vs 24 bit output of the same 16/44.1 file, playing the same files using different playback software, using a high-jitter Google Chromecast optical out, and between my three different computer optical interfaces. I believe it's all to do with electrical noise and timing distortion created inside the FPGA as it does different kinds of processing. The Mojo is amazing, but my experience has shown me that it can only sound its best with a clean input.

Good post but possible internal fpga distortion is getting in to the obsessive zone im not keen on.

 

[musickid]

Nano scale digital signal processing is better.

 

[adeseaso]

It does look like an interesting piece of kit, so your feedback will be interesting to posters.

Agreed, I got a wide delivery window but I'll report back once I've gotten a hang of the device.

 

[Audiotistic]

I recently picked up a Mojo and I'm absolutely in love with it! I've been using it as a desktop dac and while plugged in it gets pretty warm. Now I know this is nothing new to most of you, but I found a neat little trick that works very very well to keep it nice and cool. I'm also into building computers and I just happened to have a Noctua NH D15 sitting around doing nothing. I just set it right on top and now the Mojo is cold to the touch while plugged in and charging.

The NH D15 is a massive double tower heatpipe cpu cooler (one of, if not the, best air coolers for a cpu you can buy) so it's probably overkill, but man does it work wonders. You could probably get away with using a cheap tower cooler, like a Cooler Master 212 Evo, or something along those lines. I really wasn't expecting this to work so well but it does, and now this is how it will live on my desk.

Also for those wondering, the cold plate on the cooler is polished and smooth with no sharp corners, so there is no chance of damaging the finish on the mojo.

 

[surfgeorge]

Poly is too rich for me.


So, I have got Hiby R3 with Shanling L2 Type-C to Micro USB Audio Cable and Chord Mojo. That is a perfect combo. No Jitter or cracking noise with Shanling L2 cable. I highly advice to buy this cable.

...and you can get the HiBy 3,5mm coax cable for a smoother sound if preferred.
I have both and have been using them alternatively.
The FIIO CL06 is a cheaper alternative to the Shanling L2, and I don't remember hearing a difference. The L2 looks much better though

 

[Deftone]

I recently picked up a Mojo and I'm absolutely in love with it! I've been using it as a desktop dac and while plugged in it gets pretty warm. Now I know this is nothing new to most of you, but I found a neat little trick that works very very well to keep it nice and cool. I'm also into building computers and I just happened to have a Noctua NH D15 sitting around doing nothing. I just set it right on top and now the Mojo is cold to the touch while plugged in and charging.

The NH D15 is a massive double tower heatpipe cpu cooler (one of, if not the, best air coolers for a cpu you can buy) so it's probably overkill, but man does it work wonders. You could probably get away with using a cheap tower cooler, like a Cooler Master 212 Evo, or something along those lines. I really wasn't expecting this to work so well but it does, and now this is how it will live on my desk.

Also for those wondering, the cold plate on the cooler is polished and smooth with no sharp corners, so there is no chance of damaging the finish on the mojo.

It gets so hot it keeps shutting off? My mojo gets quite warm occasionally but it's never caused an issue.

 

[Audiotistic]

It gets so hot it keeps shutting off? My mojo gets quite warm occasionally but it's never caused an issue.

No, I never said it shuts off? It just gets a little too warm for my liking.

 

[miketlse]

No, I never said it shuts off? It just gets a little too warm for my liking.

Mojo contains 3 thermal sensors, that switch it off if it gets too hot.
To reduce the temperature, you just need to stand the mojo on its side - that is a lot simpler than fixing a giant cpu cooler to it.

mojo will generate the most heat, if you play music, plus charge the Mojo from a low battery status at the same time.

 

[Deftone]

No, I never said it shuts off? It just gets a little too warm for my liking.

Well I assumed the high temperature was causing problems for you otherwise why would you use such a large heatsink.