Chord Mojo

[pl_svn]

bought a Chord Mojo about one month ago and loving it

purchased for using it as portable dac/amp for my iPhone

 

tried, a few days ago, using it in my main system: Mac mini (running Roon) > Auralic Aries (in RoonReady mode) > USB Regen > Mojo

sounds great indeed and I really enjoyed it the whole afternoon. also tried a couple of DSD, which my DAC doesn't do.

 

then, at the end of the session, I reconnected my DAC (Metrum Hex, fed by an Audiophilleo) and tried playing a couple of good redbook tracks. well... there's no story! but obviously the comparison wasn't fair at all

 

so I ordered a RaspBerry Pi and an HiFiBerry Digi+ (again a RoonReady solution) and will use the Mojo with headphones when I'm too lazy to warm up the tubes

[skyline]

I have a Mojo with Regen, Curious link, and Curious USB micro.

 

It's sensitive to USB cables as I've gone from Audioquest Coffee, Oyaide d+, to Curious USB.

 

It's jumped in performance with every USB cable upgrade.

[skyline]

Best Mojo setup so far:

 

Regen plus Curious link and USB cable.

 

Bakoon BPS-2 powering the Regen.

 

This is big step up from listening to the Mojo straight out of an iPhone 6s.

[christopher3393]

I use the Mojo with a Regen and Curious link. Bakoon BPS-2 powers the Regen.

 

Adding the Curious link and Bakoon was a bigger leap than the Regen itself.

 

Wondering what headphones you use?

[skyline]

Wondering what headphones you use?

 

Aurisonics 2.5

[muski]

For me the best-sounding Mojo setup is HD-Plex powered µRendu->Curious Link->Mojo feeding Fostex TH-900Mk2 (Lawton modded). So detailed and with so much power, but so 'analog' and not fatiguing.

 

But it's far from portable! Using a Regen with an iPhone/iPad seems like a great idea. I'll have to try it...

[franz159]

I also think many underestimate Mojo or Hugo's capabilities because of the presence or need for pre-amplification. I think the main reason why you found Hugo TT to be close to Ayre QB9-DSD is because of the need for a pre-amplifier in-between. Using Chord's internal digital volume control and bypassing a pre-amplifier really adds much more transparency and allows you to hear more into the DAC's unique qualities. I certainly found this to be true with Chord Mojo.

 

Hi, I noticed you mentioned multiple times using Chord MoJo bypassing the pre-amplification stage.

Does this mean that - according to your experience - the loss in bit depth and resolution which is usually taking place with digital volume attenuation is less noticeable and it is therefore "acceptable"? Could you please elaborate?

Thanks!

[ecwl]

Hi, I noticed you mentioned multiple times using Chord MoJo bypassing the pre-amplification stage.

Does this mean that - according to your experience - the loss in bit depth and resolution which is usually taking place with digital volume attenuation is less noticeable and it is therefore "acceptable"? Could you please elaborate?

So I don't recall the designer Rob Watts ever specifying the actual bit depth of Mojo. I presume it's at least 32-bit because he sometimes displays 1kHz spectrum of Mojo with the noise floor measured at -180dB and higher order harmonic distortions at < -120dB. So for playing 16-bit files, you have -96dB room for attenuation and for playing 24-bit files, you still have -48dB room for digital volume attenuation without losing bit depth. Rob Watts also recommends using Mojo's volume control, not the PC's digital volume attenuation because he said his digital volume attenuation is done at a high sample rate and he uses more sophisticated noise shaping algorithms internally than we would be able to with our PCs. The resolution/noise floor/dynamic range perspective is more complicated. The real issue is that whether you use digital volume attenuation within the DAC, or whether you actually feed a 2V/3V signal out of the Mojo into a passive or active preamplifier, you're still losing resolution, raising noise floor, reducing dynamic range and adding distortions. In the case of the Mojo, it would be exceedingly rare to find an active or even a passive preamplifier that is not causing a more significant loss in resolution, a higher level of noise floor, a greater reduction in dynamic range and the addition of more harmonic and non-harmonic distortion to the signal, compared to bypassing the external preamplifier and simply using the Mojo's digital volume control. This is probably also true for most SDM-based chip DACs, e.g. Sabre DACs, but may not be true for DSD/R2R DACs depending on their degree of low-level linearity. Of course, the output stage of the DAC also matters because if that has a lot of distortions with low-level signals, you're obviously better off putting out a 2V/3V signal and letting a passive preamplifier attenuate that signal, instead of digitally sending the signal out. Bottom line as I said on the other forum thread is that you should really try listening to Mojo without a preamplifier for at least a few hours just to see if you enjoy the sound or not. The removal of distortions sometimes sound less dynamic or softer or even drier. Harmonic distortions can also artifically warm up the sound and expand soundstage to poorly recorded music. Unfortunately, we are used to the sonic presentation of our music through our old DACs and preamplifiers. Hence, it takes a bit of time for the ears to adjust to the extra details, resolution, soundstage and timbral quality of the instruments of our different recordings. Great recordings will sound better but mediocre ones may have a smaller soundstage and a drier sound as a result but the extra detail, resolution and a more accurate timbral quality from these inferior recordings should still shine through. It comes down to what you're looking for in a DAC. The more transparent a DAC, even though it should always be euphonic, the more likely a DAC should show the difference between a superbly recorded recording vs a mediocre recording. But if the purpose of the DAC/preamplifier combo is to make the sound of all recordings more pleasing, we are essentially sacrificing some degree of transparency for additional euphonic noise/distortions.

[mansr]

So I don't recall the designer Rob Watts ever specifying the actual bit depth of Mojo. I presume it's at least 32-bit because he sometimes displays 1kHz spectrum of Mojo with the noise floor measured at -180dB and higher order harmonic distortions at < -120dB. So for playing 16-bit files, you have -96dB room for attenuation and for playing 24-bit files, you still have -48dB room for digital volume attenuation without losing bit depth.

 

You can't compare numbers like that. A spectrum plot shows power per Hz. A noise floor of -180 dB corresponds to about 21 bits of actual resolution (there's also a dependency on sample rate), which is very good indeed. It is physically impossible to exceed about 22 bits of effective resolution at room temperature due to thermal noise.

[ecwl]

You can't compare numbers like that. A spectrum plot shows power per Hz. A noise floor of -180 dB corresponds to about 21 bits of actual resolution (there's also a dependency on sample rate), which is very good indeed. It is physically impossible to exceed about 22 bits of effective resolution at room temperature due to thermal noise.

You're absolutely right. My comment was specifically referring to the fact that I do not know to what degree of bit depth Chord's volume attenuation is performed under. And so I'm suspecting that it is at least to 32-bit accuracy based on Rob Watt's APX555 measurements. The comment is in no way referring to the Chord Mojo performance in actual use. As you know, some companies like Resonessence would say their digital volume control is 32-bit accurate, or NAD would say their DAC runs at 35-bit or Naim would say their DSP is 40-bit (even though it doesn't do volume control). Since Rob Watts never comments on it, it leaves one to speculate. But accurate digital computation without loss of digital resolution as you pointed out has no bearing on actual analog performance.

[mansr]

You're absolutely right. My comment was specifically referring to the fact that I do not know to what degree of bit depth Chord's volume attenuation is performed under. And so I'm suspecting that it is at least to 32-bit accuracy based on Rob Watt's APX555 measurements. The comment is in no way referring to the Chord Mojo performance in actual use. As you know, some companies like Resonessence would say their digital volume control is 32-bit accurate, or NAD would say their DAC runs at 35-bit or Naim would say their DSP is 40-bit (even though it doesn't do volume control). Since Rob Watts never comments on it, it leaves one to speculate. But accurate digital computation without loss of digital resolution as you pointed out has no bearing on actual analog performance.

The normal thing is to perform calculations in 32-bit or better precision, then dither to the resolution of the DAC chip, typically 24 bits. If this is done correctly, the amount of attenuation possible without losing significant information depends only on the input signal and the analogue performance of the DAC. If the input is already barely above the noise level of the DAC, no attenuation is possible without loss no matter how many bits you use.

 

Without noise shaping, 16-bit data has a dynamic range of roughly 100 dB. The best DACs achieve around 130 dB, giving you 30 dB of headroom for attenuation. 24-bit input can already contain signal elements below the capability of the DAC to reproduce, so no attenuation is perfectly safe there. Of course, most music is recorded at much higher levels, meaning in practice there is usually some headroom anyway. How much depends on the recording.

 

I guess what you're trying to say is that the digital volume control on the Mojo is no worse than these constraints. I'd be quite surprised if it were since doing it right isn't especially difficult. This is not the same as having 96 dB headroom with 16-bit input. That's impossible.

[Miska]

Without noise shaping, 16-bit data has a dynamic range of roughly 100 dB. The best DACs achieve around 130 dB, giving you 30 dB of headroom for attenuation. 24-bit input can already contain signal elements below the capability of the DAC to reproduce, so no attenuation is perfectly safe there. Of course, most music is recorded at much higher levels, meaning in practice there is usually some headroom anyway. How much depends on the recording.

 

I guess what you're trying to say is that the digital volume control on the Mojo is no worse than these constraints. I'd be quite surprised if it were since doing it right isn't especially difficult. This is not the same as having 96 dB headroom with 16-bit input. That's impossible.

 

Of course depending on what you compare against. In most cases, digital volume controls are much better quality than analog implementations. Analog volume controls usually introduce resistance to the signal path and thus increasing noise levels due to thermal noise.

 

For example ESS Sabre has equivalent resistance of about 600 ohm resistor. Many analog preamplifiers end up having much higher resistances on the path and thus increased noise. Digital volume control of course doesn't introduce any electrical changes to the signal path.

 

When looked end-to-end, to power amp output, digital volume control usually doesn't have any difference in terms of noise floor, be it power amp input shorted or DAC sending signal there.

 

OTOH, DACs usually have lowest THD+N point at about -10 dBFS level.

[ismewor]

I own a Mojo as well exceptional sounding and long hours, money well spent plus the dual headphone jacks is a plus.

 

 

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[Emcee]

If I'm understanding correctly to control volume without a pre your source needs to have a volume control.

For line out you need to set it at full 3V by depressing all buttons at power up. You'll be feeding full volume into your amp. I'm a bit wary of doing that for fear of accidentally blowing up my speakers.

[ecwl]

If I'm understanding correctly to control volume without a pre your source needs to have a volume control.

For line out you need to set it at full 3V by depressing all buttons at power up. You'll be feeding full volume into your amp. I'm a bit wary of doing that for fear of accidentally blowing up my speakers.

 

That's not true. Mojo has digital attenuation volume control so the best sound (assuming we are not talking about HQPlayer) is to have the computer send bit-perfect full volume audio to the Mojo and then use Mojo's digital volume attenuation and not set it to line out if you're directly hooking it up to your amp. Since Mojo remembers your last volume setting, you can make sure you lower the volume of the Mojo so you won't blow the amp. The mistake I sometimes make is that I accidentally didn't set the computer source to full volume so I'm not playing bitperfect audio into the Mojo and that can and usually does affect the sound depending on the source. In fact, I was using Airplay to send music from my iPad to my Airport Express via Toslink into Mojo last night and I had to remember to turn up the volume of the iPad and turn down the volume of the Mojo to get the best sound.

 

 

Sent from my iPad using Computer Audiophile

[Emcee]

That's not true. Mojo has digital attenuation volume control so the best sound (assuming we are not talking about HQPlayer) is to have the computer send bit-perfect full volume audio to the Mojo and then use Mojo's digital volume attenuation and not set it to line out if you're directly hooking it up to your amp. Since Mojo remembers your last volume setting, you can make sure you lower the volume of the Mojo so you won't blow the amp. The mistake I sometimes make is that I accidentally didn't set the computer source to full volume so I'm not playing bitperfect audio into the Mojo and that can and usually does affect the sound depending on the source. In fact, I was using Airplay to send music from my iPad to my Airport Express via Toslink into Mojo last night and I had to remember to turn up the volume of the iPad and turn down the volume of the Mojo to get the best sound.

 

 

Sent from my iPad using Computer Audiophile

 

OK I was under the impression that was only for driving headphones. So in that case full volume should be equivalent to the 3V of the line out.

[Miska]

In fact, I was using Airplay to send music from my iPad to my Airport Express via Toslink into Mojo last night and I had to remember to turn up the volume of the iPad and turn down the volume of the Mojo to get the best sound.

 

Especially because Airplay through Airport Express is limited to 44.1/16, so the 16-bit output resolution can become limiting factor...

[TAV]

I've owned the Mojo for about 5 months, long time music lover and gear head. Etymotic ER-4PT, Mojo, iPhone/Ipad equals complete and total musical bliss. Best audio expenditure I've ever made and I've been around the block a bit.

[johnnyj]

I am using an idsd dac - any thoughts re comparisons between that and the mojo? Considering the mojo if it would be a step up in sound quality. Also, I would be using a Y adapter (not Y cable) in conjunction with my current interconnect. Thanks

[TAV]

I am using an idsd dac - any thoughts re comparisons between that and the mojo? Considering the mojo if it would be a step up in sound quality. Also, I would be using a Y adapter (not Y cable) in conjunction with my current interconnect. Thanks

 

Haven't heard the dac you mention but I can say the overall performance of the Mojo is simply stunning. My previous portable DAC was the Ibasso Mamba D4 and the Mojo is orders of magnitude better to my ears. Also, just for fun I temporarily placed the Mojo in my main sound rig, swapping out the Ayre QB9-DSD Dac and didn't feel I was giving up much .......

 

Hope that gives some perspective.

[ecwl]

For TAV, I wonder if the Mojo can even beat the Ayre if setup differently. First, Ayre would block Mac Mini's USB noise much better but if you use your iPhone in airplane mode, into the Mojo, you should get similar noise levels, thereby no disadvantaging your Mojo with the noisier Mac Mini USB output. Second, the Classe preamp may minimize the difference between Ayre and Mojo so if you plug the Mojo directly into the Classe amp and use Mojo's internal volume control... so Mac Mini + Ayre + Classe preamp + amp vs iPhone/iPad + Mojo + Classe amp. That's more of a fair fight.

 

 

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[TAV]

For TAV, I wonder if the Mojo can even beat the Ayre if setup differently. First, Ayre would block Mac Mini's USB noise much better but if you use your iPhone in airplane mode, into the Mojo, you should get similar noise levels, thereby no disadvantaging your Mojo with the noisier Mac Mini USB output. Second, the Classe preamp may minimize the difference between Ayre and Mojo so if you plug the Mojo directly into the Classe amp and use Mojo's internal volume control... so Mac Mini + Ayre + Classe preamp + amp vs iPhone/iPad + Mojo + Classe amp. That's more of a fair fight.

 

 

Sent from my iPad using Computer Audiophile

 

 

Interesting idea but I'll admit I'm not that much of a tweaker. I'll leave it by saying that I'm very happy with Mojo as my portable solution and the Aryre in the main rig.

[kennyb123]

A Mojo has been the DAC in my main system. I had been enjoying the heck out of it. The time has finally come though to move on.

 

A Hugo TT arrived yesterday. The TT is like the Mojo, but better in every way. Improved clarity, lower noise and reduced grain, greater refinement and resolution, faster, weightier and more impactful. I'm thrilled.

 

Soon I will finally get to see how the Mojo does as a portable DAC.

[mozes]

A Mojo has been the DAC in my main system. I had been enjoying the heck out of it. The time has finally come though to move on.

 

A Hugo TT arrived yesterday. The TT is like the Mojo, but better in every way. Improved clarity, lower noise and reduced grain, greater refinement and resolution, faster, weightier and more impactful. I'm thrilled.

 

Soon I will finally get to see how the Mojo does as a portable DAC.

 

Congrats on your Hugo TT! Question, did you consider the 2qute when you were evaluating DACs?

 

 

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[kennyb123]

Congrats on your Hugo TT! Question, did you consider the 2qute when you were evaluating DACs?

 

Yes.

 

The decision came down mostly to power. Recent moves have considerably dropped the noise floor in my system. I wanted to continue down that path.

 

The TT is isolated from AC thanks to the battery and ultracapacitors. My microRendu is isolated as well thanks to ultracapacitors in the LPS-1. As the Mojo was battery powered, there was definitely a huge appeal to sticking with the same (or better) isolation from AC.

 

Another plus with the TT (and Mojo) is that there is no need for a good aftermarket power cord. Every AC-powered DAC that I've owned has benefitted much from one of these.

 

There are some reports that suggest the 2Qute benefits from a really good linear supply. That factored into my decision as well in terms of the cost - as did the appropriate Shunyata power cord to power the linear supply. Adding these of course brought the price much closer. Without actually trying these with the 2Qute, I can't know for sure that these would have been something I would have wanted to pursue. But since I was able to get a good deal on a TT, it became a moot issue.