This is a review and detailed measurements of Chord Mojo portable DAC and headphone amplifier. It is on a kind loan from a member. Retail price is USD $599 but I see Amazon showing it for $532 including prime shipping.
The Mojo is a small but chunky and heavy as portable headphone amplifiers go:
The case feels like it is filled with lead and you could run a car on top of it and have it escape unscathed.
Let me get out of the way that I am not a fan of its whimsical look. But much worse is forcing a human to decode hues and color intensity of lights to detect what mode the unit is in. Why oh why? For $600, I expect something more informative than what is offered here. I will for example happily take a rotary volume control over those two blue buttons for volume level.
The Chord products are popularized by its designer, Rob Watts who is quite active online, and in audio shows/conferences. Having technical designers mingle with social media community has been proven to be a successful formula and this is no exception. In one of the talks Rob mentioned they had sold something like 70,000 Chord Mojos!
Rob's approach to building DACs is rather unique and involves his own custom DAC implemented in an ASIC (custom integrated circuit) [EDIT: it uses and FPGA which is like an ASIC but programmable over and over again]. The reason for shunning off-the-shelf DACs is that Rob believes in very high precision filters for upsampling and reconstruction. Convinced by his own experiments (sighted and unscientific unfortunately), he believes the more precision he puts in these filters, the better the sound gets. He has taken this to incredible extremes in his higher-end DACs but that formula also exists in this little unit.
The drawback to his approach is power consumption and heat. The Mojo sitting there doing nothing runs warm. With use it gets even warmer making me concerned for lifetime of any battery in there. Batteries don't like to be charged when warm and here, that will be the rule, not the exception. All that heat could also go to producing sound instead of wasting battery life.
Are the compromises worth it? Let's measure the unit and see. Note that all tests are done with USB input.
Measurements
This review will be much more detailed than my usual ones since Chord DACs are sold on basis of technical claims. As I typically do, I start with testing the DAC portion of the unit and then the headphone amplifier. Since there is no separate line out, I resort to setting the output to 2 volts. There is a mode to put the unit in "line-out" mode but it produces too high a voltage of 3 volts which degrades the performance. I don't know where the notion of 3 volt comes from other than wanting to make sure the unit sounds louder than others. Due to steppingstones of the volume control, I could not get to exact 2 volt output but that shouldn't matter. Let's get our dashboard view and see the state of union:
Chord specifies Mojo distortion at 0.00017%. We are missing that by a fair bit at 0.00086%. Sadly Chord spec shows no measurement conditions (e.g. weighted or not) so no way of knowing how to try to match their numbers.
A bit worrying was highly variable response. I was getting SINAD numbers jumping from 99 to 105. The above snapshot randomly captured 101. I usually see some variations but not 6 dB. Regardless, using a 102 dB SINAD puts the Mojo solidly at the bottom of our tier 2 DAC performance:
That puts it in the same category of portable units like Topping NX4 DSD (retail $150). Rather disappointing.
Let's look at intermodulation distortion versus level:
I happen to have the Topping DX3Pro ($250) in my template so I left it there as a reference. We see that Chord Mojo has uniformly higher noise level (and hence worse THD+N/SINAD). But also has a kink in the curve where intermodulation distortion overtakes noise at around -25 dB. Some kind of non-linearity is setting in. Not sure if this is in the DAC portion or amplification. Either way, there should be better performance here.
The Chord Mojo redeems itself with very good jitter spectrum:
This is my new high resolution test so we are liable to see spikes but they are all well below audibility by any stretch.
Linearity is very good (and beats DX3Pro) but it is not textbook perfect:
Many DACs achieve less than 0.5 dB of error at -120 dB but the Mojo DAC misses that mark.
Dynamic range is 9 dB shy of the spec:
Since there is so much talk about the filter component of Chord DACs, I ran a few tests to characterize that. Here is the response to square wave:
We get a "free" multitone response out of that in frequency domain since a square wave is a tone with infinite odd harmonics:
An ideal system would have a response at 1, 3, 5, 7, etc. kHz. We see those spikes but also get fair amount of "grass" growing at their feet with spurious spikes.
There is also an odd rise in low frequencies. Not sure what this is about. Fortunately we are pretty deaf in that region so not an audible concern.
Running white noise through a DAC shows the response of the reconstruction filter since such a noise has infinite bandwidth:
An ideal DAC would have infinite attenuation outside of the our required band (22.05 kHz at 44.1 kHz). No DAC is perfect though and here we see an attenuation of 80 dB.
Zooming into the transition band (from full bandwidth to filtered) we see the bandwidth of the filter:
So the transition region is about 370 Hz. I will try to measure this on other DACs from time to time so we have more frame of reference. Personally though, I am as interested in such things as watching paint dry.
But I know some of you like to see them so I will provide them as time allows.
I think we are done with the DAC portion. Let's see how how much power we can get out of this unit with headphone loads started with 300 ohm:
Here again I had the Topping DX3Pro results already in the template. As we see, the Chord graph is rather choppy and as indicated by the letter "T," is frustrating the analyzer by not providing a stable output -- same issue we saw in the dashboard. I actually relaxed the criteria (hence the choppiness of the graph) to get any results.
We see decent amount of power here although once again, less than DX3Pro. Same was true at 33 ohm:
The output was more stable here, producing 410 milliwatts of power prior to clipping. This is pretty good amount of power for a small battery operated unit.
Output impedance is satisfyingly low at just 0.7 ohm:
So it should be able to drive any headphone and not impact its frequency response.
Finally, let's look at channel balance versus volume control level:
We have perfect result of 0 dB deviation due to use of digital controls. The up/down buttons change level by 1 dB linearity forever as shown in the graph. That is perceptually not correct but it does the job.
Listening Tests
As usual I start my listening tests with 300 ohm Sennheiser HD-650 headphone. Using my usual test clips, the Chord Mojo got quite loud but as the saying goes, "it got scared before I did." Namely, I could get it loud enough to start to get distorted/buzz/crackle some with bass getting distorted. This was at very high volumes though so not a problem for just about anyone.
There was more power (as there usually is) with my HiFiMan HE-400i generating a very satisfying experience.
No, I did not detect any magical qualities due to the filter or DAC design.
Conclusions
There is really nothing broken in Chord Mojo. It performs well in a variety of tests. The issue with it is so much technical hype about its superiority that one is left empty after seeing performance that is well below state-of-the-art. We have DACs at less than half the price easily outperforming it on many tests. I cannot see any technical benefit to its design approach. On the contrary, that approach brings with it much higher cost, and power consumption. Combine that with the poor user interface and the Chord Mojo is simply not my cup of tea.
Again, the Mojo is a competent product unlike some other boutique DACs that compete with each other to see who can produce worse performance. It goes a different route but leaves the road well paved. So if you are attracted to it, I am not going to sit here and tell you that you should not buy it.
A rant: Rob Watts owns an audio precision analyzer which he uses for the design of his DACs. Why on earth then are his specs are shorter than markings on a car tire? Why not post full measurement report? This review is going to garner some amount of angst among people. To short circuit that, I am going to remind you that the only answer to my review is manufacture posting similar measurements showing different results. That they don't do that, is a more serious problem than any conflict between the data I have and what is claimed.
-------------
As always, questions, comments, recommendations, etc. are welcome.
If you like this review, please consider donating funds using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
The Mojo is a small but chunky and heavy as portable headphone amplifiers go:
The case feels like it is filled with lead and you could run a car on top of it and have it escape unscathed.
Let me get out of the way that I am not a fan of its whimsical look. But much worse is forcing a human to decode hues and color intensity of lights to detect what mode the unit is in. Why oh why? For $600, I expect something more informative than what is offered here. I will for example happily take a rotary volume control over those two blue buttons for volume level.
The Chord products are popularized by its designer, Rob Watts who is quite active online, and in audio shows/conferences. Having technical designers mingle with social media community has been proven to be a successful formula and this is no exception. In one of the talks Rob mentioned they had sold something like 70,000 Chord Mojos!
Rob's approach to building DACs is rather unique and involves his own custom DAC implemented in an ASIC (custom integrated circuit) [EDIT: it uses and FPGA which is like an ASIC but programmable over and over again]. The reason for shunning off-the-shelf DACs is that Rob believes in very high precision filters for upsampling and reconstruction. Convinced by his own experiments (sighted and unscientific unfortunately), he believes the more precision he puts in these filters, the better the sound gets. He has taken this to incredible extremes in his higher-end DACs but that formula also exists in this little unit.
The drawback to his approach is power consumption and heat. The Mojo sitting there doing nothing runs warm. With use it gets even warmer making me concerned for lifetime of any battery in there. Batteries don't like to be charged when warm and here, that will be the rule, not the exception. All that heat could also go to producing sound instead of wasting battery life.
Are the compromises worth it? Let's measure the unit and see. Note that all tests are done with USB input.
Measurements
This review will be much more detailed than my usual ones since Chord DACs are sold on basis of technical claims. As I typically do, I start with testing the DAC portion of the unit and then the headphone amplifier. Since there is no separate line out, I resort to setting the output to 2 volts. There is a mode to put the unit in "line-out" mode but it produces too high a voltage of 3 volts which degrades the performance. I don't know where the notion of 3 volt comes from other than wanting to make sure the unit sounds louder than others. Due to steppingstones of the volume control, I could not get to exact 2 volt output but that shouldn't matter. Let's get our dashboard view and see the state of union:
Chord specifies Mojo distortion at 0.00017%. We are missing that by a fair bit at 0.00086%. Sadly Chord spec shows no measurement conditions (e.g. weighted or not) so no way of knowing how to try to match their numbers.
A bit worrying was highly variable response. I was getting SINAD numbers jumping from 99 to 105. The above snapshot randomly captured 101. I usually see some variations but not 6 dB. Regardless, using a 102 dB SINAD puts the Mojo solidly at the bottom of our tier 2 DAC performance:
That puts it in the same category of portable units like Topping NX4 DSD (retail $150). Rather disappointing.
Let's look at intermodulation distortion versus level:
I happen to have the Topping DX3Pro ($250) in my template so I left it there as a reference. We see that Chord Mojo has uniformly higher noise level (and hence worse THD+N/SINAD). But also has a kink in the curve where intermodulation distortion overtakes noise at around -25 dB. Some kind of non-linearity is setting in. Not sure if this is in the DAC portion or amplification. Either way, there should be better performance here.
The Chord Mojo redeems itself with very good jitter spectrum:
This is my new high resolution test so we are liable to see spikes but they are all well below audibility by any stretch.
Linearity is very good (and beats DX3Pro) but it is not textbook perfect:
Many DACs achieve less than 0.5 dB of error at -120 dB but the Mojo DAC misses that mark.
Dynamic range is 9 dB shy of the spec:
Since there is so much talk about the filter component of Chord DACs, I ran a few tests to characterize that. Here is the response to square wave:
We get a "free" multitone response out of that in frequency domain since a square wave is a tone with infinite odd harmonics:
An ideal system would have a response at 1, 3, 5, 7, etc. kHz. We see those spikes but also get fair amount of "grass" growing at their feet with spurious spikes.
There is also an odd rise in low frequencies. Not sure what this is about. Fortunately we are pretty deaf in that region so not an audible concern.
Running white noise through a DAC shows the response of the reconstruction filter since such a noise has infinite bandwidth:
An ideal DAC would have infinite attenuation outside of the our required band (22.05 kHz at 44.1 kHz). No DAC is perfect though and here we see an attenuation of 80 dB.
Zooming into the transition band (from full bandwidth to filtered) we see the bandwidth of the filter:
So the transition region is about 370 Hz. I will try to measure this on other DACs from time to time so we have more frame of reference. Personally though, I am as interested in such things as watching paint dry.
But I know some of you like to see them so I will provide them as time allows.I think we are done with the DAC portion. Let's see how how much power we can get out of this unit with headphone loads started with 300 ohm:
Here again I had the Topping DX3Pro results already in the template. As we see, the Chord graph is rather choppy and as indicated by the letter "T," is frustrating the analyzer by not providing a stable output -- same issue we saw in the dashboard. I actually relaxed the criteria (hence the choppiness of the graph) to get any results.
We see decent amount of power here although once again, less than DX3Pro. Same was true at 33 ohm:
The output was more stable here, producing 410 milliwatts of power prior to clipping. This is pretty good amount of power for a small battery operated unit.
Output impedance is satisfyingly low at just 0.7 ohm:
So it should be able to drive any headphone and not impact its frequency response.
Finally, let's look at channel balance versus volume control level:
We have perfect result of 0 dB deviation due to use of digital controls. The up/down buttons change level by 1 dB linearity forever as shown in the graph. That is perceptually not correct but it does the job.
Listening Tests
As usual I start my listening tests with 300 ohm Sennheiser HD-650 headphone. Using my usual test clips, the Chord Mojo got quite loud but as the saying goes, "it got scared before I did."
Namely, I could get it loud enough to start to get distorted/buzz/crackle some with bass getting distorted. This was at very high volumes though so not a problem for just about anyone.There was more power (as there usually is) with my HiFiMan HE-400i generating a very satisfying experience.
No, I did not detect any magical qualities due to the filter or DAC design.
Conclusions
There is really nothing broken in Chord Mojo. It performs well in a variety of tests. The issue with it is so much technical hype about its superiority that one is left empty after seeing performance that is well below state-of-the-art. We have DACs at less than half the price easily outperforming it on many tests. I cannot see any technical benefit to its design approach. On the contrary, that approach brings with it much higher cost, and power consumption. Combine that with the poor user interface and the Chord Mojo is simply not my cup of tea.
Again, the Mojo is a competent product unlike some other boutique DACs that compete with each other to see who can produce worse performance. It goes a different route but leaves the road well paved. So if you are attracted to it, I am not going to sit here and tell you that you should not buy it.
A rant: Rob Watts owns an audio precision analyzer which he uses for the design of his DACs. Why on earth then are his specs are shorter than markings on a car tire? Why not post full measurement report? This review is going to garner some amount of angst among people. To short circuit that, I am going to remind you that the only answer to my review is manufacture posting similar measurements showing different results. That they don't do that, is a more serious problem than any conflict between the data I have and what is claimed.
-------------
As always, questions, comments, recommendations, etc. are welcome.
If you like this review, please consider donating funds using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
Last edited:
