CHORD Mojo 2 Review (Portable DAC & HP Amp)

[bitonio]

Thanks @amirm, I am not sure I'll be brave enough to take that route Your instructions are clear, yet my hands are not steady and tend to break stuff.
The L30 II is arriving Monday, if this turn out to be the Jot v1 the culprit 1/ I'll know the fix if I need it 2/ My trust in Schiit will take a hit.

@Jimster480 definitely more news sometime next week.

 

[Ken Tajalli]

There is a manufacturing/design issue with Jot that induces hum. See my fix here: https://www.audiosciencereview.com/...otunheim-headphone-amplifier.3733/#post-89406

well spotted!
the device is living up to its name then!
Just joking.

 

[bitonio]

I finally was able to get time to pair the Mojo2 with the L30 II and spend some time with the combo.

• The L30 II output is much cleaner that the Jot v1
• The details retrieved by the Mojo find their place in "space" much better than with the Mojo alone, very good surprise
• Overall, the combo adds some smoothness, laid back that makes the music less forward, I like it
• When pushing the volume on a fairly dark background (track Nameless from Dominique Fils-Aimé) a very faint static noise can be heard
  • It appears around 2 O'clock on L gain with Mojo on high volume + blue-purple-ish color
  • Bear in mind using a fairly easy to drive dynamic headphones (Focal Elegia)
  • The noise is way, WAY lower than with the Jot v1, I find it acceptable

I tried the very same combo running the Mojo purely on its battery, the same faint background noise was still there.
I'll share more feedback on the little amp on its dedicated thread. It is a fine little amp for its price, getting a volume knob (even cheap like this) is a big plus for me since I also use the same headphone for video call and the audio can get from very low to very high so need to quickly crank up or down.

 

[Jimster480]

I finally was able to get time to pair the Mojo2 with the L30 II and spend some time with the combo.

• The L30 II output is much cleaner that the Jot v1
• The details retrieved by the Mojo find their place in "space" much better than with the Mojo alone, very good surprise
• Overall, the combo adds some smoothness, laid back that makes the music less forward, I like it
• When pushing the volume on a fairly dark background (track Nameless from Dominique Fils-Aimé) a very faint static noise can be heard
  • It appears around 2 O'clock on L gain with Mojo on high volume + blue-purple-ish color
  • Bear in mind using a fairly easy to drive dynamic headphones (Focal Elegia)
  • The noise is way, WAY lower than with the Jot v1, I find it acceptable

View attachment 227658

I tried the very same combo running the Mojo purely on its battery, the same faint background noise was still there.
I'll share more feedback on the little amp on its dedicated thread. It is a fine little amp for its price, getting a volume knob (even cheap like this) is a big plus for me since I also use the same headphone for video call and the audio can get from very low to very high so need to quickly crank up or down.

is it possible that the noise comes from the song itself or is it always present? It might be an issue with the mojo itself. Not sure if you have warranty and can get that checked out or not. Glad you are liking the L30 though; I figured you would enjoy it!

 

[bitonio]

is it possible that the noise comes from the song itself or is it always present? It might be an issue with the mojo itself. Not sure if you have warranty and can get that checked out or not. Glad you are liking the L30 though; I figured you would enjoy it!

I don't think it comes from the tracks, I picked some I know particularly well and the background is totally silent on the Mojo alone, or my Jot v1. Only the combo Mojo+amp is showing some faint noise. It is really hard to pick, at volume I'd never use even on a low volume source. Maybe it is the Mojo and I don't feel venturing a return/exchange [got it abroad, which mean international shipping, custom forms, etc...].

 

[Jimster480]

I don't think it comes from the tracks, I picked some I know particularly well and the background is totally silent on the Mojo alone, or my Jot v1. Only the combo Mojo+amp is showing some faint noise. It is really hard to pick, at volume I'd never use even on a low volume source. Maybe it is the Mojo and I don't feel venturing a return/exchange [got it abroad, which mean international shipping, custom forms, etc...].

Ah, Yea I guess the background noise comes from the MOJO itself then.

 

[bitonio]

New experimentation, your point of noise coming from the track got me thinking.
I found a discussion in this forum and someone generated a WAV file with very little noise, almost silent:
https://www.audiosciencereview.com/...se-to-test-for-system-hiss.17816/#post-578717

I picked it up and tested it with my setup, and guess what the combo Mojo+L30II is dead silent.
I am not sure what to conclude other than there's nothing wrong with the Mojo or the combo Mojo + Amp.
I still think my copy of the Jot v1 has a grounding issue as Amir pointed it out
I also think the Jot v1 Multi-bit removes the recorded noise or, not able to extract it as well as the mojo does.

 

[Jimster480]

New experimentation, your point of noise coming from the track got me thinking.
I found a discussion in this forum and someone generated a WAV file with very little noise, almost silent:
https://www.audiosciencereview.com/...se-to-test-for-system-hiss.17816/#post-578717

I picked it up and tested it with my setup, and guess what the combo Mojo+L30II is dead silent.
I am not sure what to conclude other than there's nothing wrong with the Mojo or the combo Mojo + Amp.
I still think my copy of the Jot v1 has a grounding issue as Amir pointed it out
I also think the Jot v1 Multi-bit removes the recorded noise or, not able to extract it as well as the mojo does.

Well the multi-bit unit has terrible linearity so it always loses details. It's just due to the multi-bit DAC that they actually use in the device. It's not meant for audio.
Maybe the hiss comes from your player? What software are you using?

 

[bitonio]

Using Audirvana (exclusive mode on the DAC) and Roon. I really doubt the hiss comes from the player as the demo file from the other thread comes dead silent on L30II+Mojo2. I will do the same test with the Jot v1 + Mojo2 and I expect the hiss to be there, likely because of the grounding issue.

That's all good, thanks for the help of many of you, I have been able to confirm my Mojo2 is just fine, the L30II is a nice little toy and my home/old setup while still giving me satisfaction is not perfect

 

[formantzero]

Question for you guys. I’d like to use my Mojo 2 in a desktop setting as well, which has the added benefit of adding tone controls and crossfeed with my headphones (Lyric and Stellia which need EQ).

Idea:

MOTU 624 audio interface (connected to laptop via low latency Thunderbolt 2)
—> connect to the optical input of the Mojo 2 via TOSLINK
—> connect one of the Mojo 2 outputs via 3.5mm to RCA cable to the SE inputs of the THX AAA 789
—> connect via balanced 4-pin XLR to the headphones (SE input selected on the 789)

Question is this — Mojo 2 removed line out mode for usability reasons but they say you can achieve the former line out level by pressing up volume 41 times in high gain mode, which should output 3V. But that’s actually a really high volume on the Mojo 2. Already a bit too loud if I was driving the Liric directly, and certainly too loud for the Stellia. So, how is that line out? Why would I require amplification? Wouldn’t the 789 basically just be attenuating if set to a comfortable volume?

The reason I’d want to use the 789 instead of the Mojo 2 directly is because I’m really happy with it as a headphone amp (low noise floor etc) and because I can use my 4-pin xlr custom braided cable which is very comfortable, not at all microphonic, and works for both the Liric and Stellia.

I guess I just assumed that line out levels required amplification, so they were pretty low. Not something that could drive the headphone directly. Which is why I was surprised at Chord’s notes on the matter of removing the line out mode.

 

[staticV3]

Modern line out levels are 2V SE, 4V Bal. Most headphones will be very loud when driven at those levels.
However, you can't plug most headphones into the line out jack of DACs, because those are not buffered and so can't drive an actual load like a headphone.
The Mojo 2 has only buffered headphone outputs and so line level out of those is plenty loud with headphones.

 

[formantzero]

So wouldn’t my 789 be essentially doing nothing if taking in a 2V or 3V input signal? I’m not sure I remember enough electrical engineering to comprehend what a buffered output is. My understanding is that all amps take an incoming electrical signal and amplify the, so that max and min voltage are much higher than they were in the input. And having an input that is”full scale” is better because the resulting amplified signal comes from an amp that has to do less work and therefore has fewer noise artifacts etc.

Line level is much much lower than what hifi amps put out to speakers, I know that much at least. But I still understood that headphone amps put out a signal much stronger than line level to headphones, esp planars.

 

[staticV3]

So wouldn’t my 789 be essentially doing nothing if taking in a 2V or 3V input signal?

The setup would be DAC(Mojo)->Headphone Amp(Mojo)->Headphone Amp(789).
In this constellation, the Mojo's Amp would be idling basically, barely outputting any current due to the 789's high input impedance.
The 789 would do the hard work of outputting the signal into a headphone load.

My understanding is that all amps take an incoming electrical signal and amplify the, so that max and min voltage are much higher than they were in the input.

An Amp has two jobs: Amplify or attenuate the incoming signal and keep it stable at high loads.
Depending on the input signal amplitude and the impedance and sensitivity of your headphones, your Amp might be doing one or the other or both to deliver a satisfying listening experience.

And having an input that is”full scale” is better because the resulting amplified signal comes from an amp that has to do less work and therefore has fewer noise artifacts etc.

Generally a high level line out and low gain from your Amp is best.

But I still understood that headphone amps put out a signal much stronger than line level to headphones, esp planars.

Depending on how you define signal strength, this may or may not be categorically true.
If you define signal strength as power ergo Watts, then yes. The signal from your Amp to your headphones will always carry more power than the signal from your DAC to your Amp.
If you define signal strength as amplitude ergo Vrms, then depending on your input signal amplitude and headphone sensitivity your Amp will either amplify or attenuate the signal before sending it to your headphones.

 

[formantzero]

Ok, you just explained something very complex in language so simple and illustrative that I think I’ve completely understood now. Thank you!

Question now is, do I set it to output 2V, or higher. Rob Watts posted on another forum how to set this to 2V, but the former Mojo 1 line level was 3V. Should I just crank this thing as high as it can go without clipping (apparently 4.3V is the threshold on the mojo 2), or do I use 2V and get the 789 to work with that? It seems like amplification is gonna happen on the Mojo 2 regardless, ,so maybe take the max it can give? And have the 789 attenuate that and deal with delivering the load into the headphone drivers?

Then again the 789 was probably designed expecting a 2V input on the SE inputs.

Also, this is Vrms, or Vmax?

 

[Jimbob54]

Ok, you just explained something very complex in language so simple and illustrative that I think I’ve completely understood now. Thank you!

Question now is, do I set it to output 2V, or higher. Rob Watts posted on another forum how to set this to 2V, but the former Mojo 1 line level was 3V. Should I just crank this thing as high as it can go without clipping (apparently 4.3V is the threshold on the mojo 2), or do I use 2V and get the 789 to work with that? It seems like amplification is gonna happen on the Mojo 2 regardless, ,so maybe take the max it can give? And have the 789 attenuate that and deal with delivering the load into the headphone drivers?

Then again the 789 was probably designed expecting a 2V input on the SE inputs.

Also, this is Vrms, or Vmax?

Per a Drop rep on the 789 discussion page :

"INPUT Maximums:
The 789 can tolerate the following rms input voltage from your DAC without clipping:
-10dB Mode: 7 V
0 dB Mode: 7 V
+10 dB Mode: 2.1 V

On the 789, the RCA unbal and XLR-3 bal have same input voltage tolerance. "

So unless you are using high gain, which I doubt you will be, get the Mojo2 set to 3v if that has the best SINAD/ SNR

As an aside, if you wanted to cut the 789 from the chain but still use your fancy XLR cable you will be able to find myriad XLR to 3.5mm adapters on ebay/ aliexpress. Around $25 should cover it.

 

[formantzero]

Per a Drop rep on the 789 discussion page :

"INPUT Maximums:
The 789 can tolerate the following rms input voltage from your DAC without clipping:
-10dB Mode: 7 V
0 dB Mode: 7 V
+10 dB Mode: 2.1 V

On the 789, the RCA unbal and XLR-3 bal have same input voltage tolerance. "

So unless you are using high gain, which I doubt you will be, get the Mojo2 set to 3v if that has the best SINAD/ SNR

As an aside, if you wanted to cut the 789 from the chain but still use your fancy XLR cable you will be able to find myriad XLR to 3.5mm adapters on ebay/ aliexpress. Around $25 should cover it.

Thanks. Yes, I had seen that post, but was still unclear on which option would have the best SINAD. The Mojo 2 set to 3V, or Mojo 2 set to 2V with the 789 doing some amplifying?

I did think about converters from 3.5 to XLR but that seemed janky, and I really love the fact that the 789 has an actual volume knob. Much better for studio use than fiddling with the Mojo 2 going directly out through 3.5mm->4-pin XLR.

I think I read in the Mojo 2 review that it has really good SINAD, so maybe cranking it even higher than 3V is a good idea, if the 789 can actually take an incoming 7V even on the RCA unbal?

 

[formantzero]

That's a fault in USB bridges made by Cmedia. A brief interruption in the USB data connection will result in full-scale white noise being sent to the DAC.
Can be caused by dust/dirt in the USB jack, strain on the USB connectors, high levels of EMI, etc.

E1DA's early products were affected by this bug as well, but since Cmedia refused to provide a fix, all current E1DA products have switched to Comtrue bridges instead.

Hopefully, Watts has made the same decision with the Mojo 2
(anyone willing to check? )

I went back and forth with Chord on this and they were less than perfectly helpful, but their basic take was: on an iPhone, only use the official Apple accessories (the Camera Connector Kit and the other one that goes lightning to USB-A female). Any other third party cables and devices like the Cayin lightning to USB-C cable (LS2-C?) have caused many a problem in their lab testing. When I told them I was getting the problem OFTEN while using an iPad with USB-C to USB-C directly, they asked me to test on a Mac.

I did, but I also switched the cable to a Thunderbolt 3 cable. Can't get higher quality than that. No problems on Mac, so I tried again with the iPad, and ended up playing 72hrs or something with no white noise bursts. So I can confirm that good cables can fix the problem.

I had previously tried 3 or 4 "high quality" USB-C cables capable of 10Gbps data transfer and even 100W Power Delivery. But they all had this issue where after an hour or two, especially playing high res audio in Tidal, I would get the white noise burst that would only go away when I interrupted the audio stream by either reconnecting the cable at either end, or pressing the siri shortcut button (seems the siri prompt sort of takes over audio and then when you cancel out of it, you can resume playback which restarts the stream).

Really strange that these cables that perform flawlessly for me in all other applications, manifested this problem with the Mojo 2, and my Thunderbolt 3 cable was eventually my saviour.

Chord didn't really say anything about that. I wonder if they care.

 

[Jimbob54]

Thanks. Yes, I had seen that post, but was still unclear on which option would have the best SINAD. The Mojo 2 set to 3V, or Mojo 2 set to 2V with the 789 doing some amplifying?

From an audibility perspective it wont matter

I think I read in the Mojo 2 review that it has really good SINAD, so maybe cranking it even higher than 3V is a good idea, if the 789 can actually take an incoming 7V even on the RCA unbal?

It can- 7v max on XLR and RCA ins for the 2 lower gain settings. I suspect at either 2v or 3v in you will be attenuating on the amp down from max in mid gain.

 

[bitonio]

I went back and forth with Chord on this and they were less than perfectly helpful, but their basic take was: on an iPhone, only use the official Apple accessories (the Camera Connector Kit and the other one that goes lightning to USB-A female). Any other third party cables and devices like the Cayin lightning to USB-C cable (LS2-C?) have caused many a problem in their lab testing. When I told them I was getting the problem OFTEN while using an iPad with USB-C to USB-C directly, they asked me to test on a Mac.

I did, but I also switched the cable to a Thunderbolt 3 cable. Can't get higher quality than that. No problems on Mac, so I tried again with the iPad, and ended up playing 72hrs or something with no white noise bursts. So I can confirm that good cables can fix the problem.

I had previously tried 3 or 4 "high quality" USB-C cables capable of 10Gbps data transfer and even 100W Power Delivery. But they all had this issue where after an hour or two, especially playing high res audio in Tidal, I would get the white noise burst that would only go away when I interrupted the audio stream by either reconnecting the cable at either end, or pressing the siri shortcut button (seems the siri prompt sort of takes over audio and then when you cancel out of it, you can resume playback which restarts the stream).

Really strange that these cables that perform flawlessly for me in all other applications, manifested this problem with the Mojo 2, and my Thunderbolt 3 cable was eventually my saviour.

Chord didn't really say anything about that. I wonder if they care.

I use the fiio LT-LT3 with my iphone no prob. I have (unfortunately) a variety of cable and usb-c hub from anker and so far never had a problem.

Thunderbolt cable as usb cable probably work better because better built.

 

[bitonio]

(…)
I think I read in the Mojo 2 review that it has really good SINAD, so maybe cranking it even higher than 3V is a good idea, if the 789 can actually take an incoming 7V even on the RCA unbal?

You can play with it, adjust the Mojo volume. I found 3V works best with my amp, not really because of SQ (to me), rather because I have a good usable range of volume on my amp volume knob in low gain.