Chord Mojo 2 Measurements

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This unit was purchased for review and my own personal use with my own funds.

ChitChat:

The Chord Mojo 2 is a very interesting device, offering Chord’s pulse array DAC design, high performance oversampling, as well as some additional features like built in DSP for EQ and Crossfeed, in a very compact package.

Subjectively, I wasn’t much of a fan of the original Mojo, but after trying the Mojo 2 at a meet I was very impressed.
Originally Chord was going to send me a review unit but I’d not been able to get ahold of them for a while so I bought one instead.

The mojo 2 sits in a bit of a unique form factor. You can’t really call it a ‘dongle’, but it isn’t a standalone DAP and does require a phone or other source device.
It also has some upgrades for use at the desk, such as an improved ‘Intelligent desktop mode’ that allows you to keep it plugged in 24/7 without degrading the battery.

Design:

Mojo 2 Internal (Battery sits on top of this PCB)

The inside of the mojo 2 shows an impressive amount of compute power for such a small device, with an ATSAM3U1C microcontroller and an ARTIX-7 FPGA.
The microcontroller is likely acting as the USB receiver, with the ARTIX-7 FPGA handling the oversampling and DSP functionality, as well as controlling the pulse array converter itself, which can be seen just to the right of the FPGA. This is what is outputting the analog signal, not the FPGA itself.
This pulse array then feeds the output stage nested between the two 3.5mm jacks. It’s a common misconception that Chord DACs don’t have an output stage, this is not the case.
Rob Watts tried to keep as few components in the signal path as possible, but they do have an output stage.

The Mojo 2 is controlled using the four RGB illuminated buttons on the front. The aesthetic of this is going to be polarising, but it fits with the rest of Chord’s line-up.
I personally found it quite tricky to remember how to configure things for the first couple days and had to have the manual constantly to hand, but after a while you do get used to it. It would have been nice to have a slightly more intuitive control scheme especially given the multitude of options to configure on the Mojo 2.

The Mojo 2 features four configurable EQ options which are adjustable upto +/- 9dB in 1dB increments.
Additionally there is a crossfeed option which many will no doubt appreciate.

The I/O is a bit on the polarising side too.
The Mojo 2 does thankfully include both a USB-C and Micro-USB port for data, so you should have no issue connecting this to any device with whatever cable you have to hand. However, you can only charge the Mojo 2 using the secondary micro-USB port.
There is also no charger in the box, so you need to ensure you have a micro-USB 5V charger with at least 2A capability before you will be able to charge the device.

The layout has been kept similar to the original Mojo so that the Chord Poly can be used with it.

Measurements:

Test Setup:

– Audio Precision APx555 B-Series Analyzer
– USB Source: Intel PC via intona 7055-C isolator
– Measurement setup and device under test are running on an AudioQuest Niagara 5000 power supply
– Audioquest Mackenzie RCA interconnects
– Mojo 2 was warmed up for 3 hours prior to testing
– Mojo 2 was in ‘intelligent desktop mode’ during testing
– Exact analyzer/filter configurations for each measurement are detailed in the full reports

A few important points to note before moving onto the measurements themselves:

1) I had the device in intelligent desktop mode as I didn’t want it to run out of battery during the testing. I did double check after and saw no performance differences at all, other than a very very slight (below -140dB) 50hz & 150hz spur in some tests. So if you see that, please disregard it as it is not there when in battery powered operation. All other tests were exactly the same. It’s great that Chord has managed to ensure the performance is effectively identical in both battery powered and desktop mode though!

2) The device was connected using an Intona 7055-C galvanic isolator. When the Mojo 2 is not isolated, it seems to show some additional noise content from about 7khz upwards. Given as the Mojo 2 is most likely to be used on the go with a phone, I think it’s most appropriate to show the performance with a low noise (and ungrounded) source anyway.

3) As I’m sure I’ll no doubt be asked about it, Amir at Audiosciencereview’s measurements show some distortion/errors that are not present in my measurements. I do not know what caused these and was not able to replicate them. But I’ve actually tested two Mojo 2 units and both performed the same, so I can only assume Amir’s unit had a fault, or there was something in the setup that caused it. His measurements did show the ultrasonic noise present when connected directly to the PC so it’s possible his PC was causing some form of issue with the Mojo 2. Portable devices such as this can often have degraded performance when using a noisier source such as a desktop PC.
https://www.audiosciencereview.com/forum/index.php?threads/chord-mojo-2-review-portable-dac-hp-amp.34160/

4) The Mojo 2 was set to 4.3V output for these tests. This is because the Mojo 2 begins clipping above this, so it is effectively the max output, and also because the volume control is entirely DSP. Therefore reducing the vol to 2V RCA line level or to a headphone listening level for the tests would just be sacrificing 6dB+ of dynamic range for no benefit.
If you’d like to see performance at 2V you can look at the -6dB or 2V point on the graphs.

Full Measurement Reports:

Reports available here:

Dynamic Range (AES17): 117.3dB (wow!)

SNR: 118.5dB

IMD SMPTE: -95.7dB

Noise Level RMS (20-20khz): 5.124uVrms

Noise Level RMS (20-90khz): 17.03uVrms

DC Offset: 247uV active, 791uV idle

Latency: 26.75ms

Susceptible to intersample overs: No (as long as you are more than 3dB below 4.3V, which you pretty much always will be)

1khz 0dBFS Sine, 4.3V output (max level without clipping):

1khz 0dBFS Sine, 2V output (RCA Line Level):

1khz 0dBFS Sine, 700mV output (Headphone Level):

1khz 0dBFS Sine, 50mV output (IEM Level):

-90.31dBFS 1khz sine (96khz capture bandwidth):

Filter Ultrasonic Attenuation:

Chord’s oversampling filter is something that they do better than any other manufacturer currently. In the case of the Mojo 2, offering a 40,960 tap filter. Leagues ahead of the usually 128-1024 tap filters in most modern DAC chips.

Idle Noise FFT:

THD+N vs Frequency:

20khz bandwidth filter
90khz bandwidth filter

The mojo 2 does have some rising THD into the higher frequencies. This persists regardless of level.
Whilst from an objective standpoint, lower THD is better, from a subjective standpoint, this can often contribute to a ‘sweeter’ or ‘warmer’ presentation which many people like.

IMD:

Linearity:

With Bandpass filter
Without Bandpass filter

Crosstalk:

Crosstalk remained constant regardless of output level

Jitter:

44.1khz USB
48khz USB

The Mojo 2 has practically perfect jitter performance. This is another thing that Chord DACs do REALLY well and is seemingly an inherent benefit of the pulse array design.
They are not ‘immune’ to jitter, but are insanely resistant to it.
Even when putting it on optical and deliberately adding 25nS of 1khz sine jitter to simulate a truly awful source device, the Mojo 2 still had very good jitter performance.

Optical, with 25nS 1khz sine jitter deliberately added

Multitone:

Wideband:

Idle Noise
1khz Sine Wideband

7 thoughts on “Chord Mojo 2 Measurements”

    • Yes, I’ve seen it before, but if you check it doesn’t exactly give setting for 4.3V. There’s a gap. So any help with my original question, as I would not trust my own measurements?

      Reply
  1. Why are you showing measurements up to 1 000 000 Hz, what do you think this will show or achieve? I guess you’re still learning how to use the AP.

    Reply
    • Only the final two measurements are taken with 1Mhz bandwidth, not the rest. And are done because showing a much wider bandwidth can often reveal useful information about noise shaping, imaging, or reveal problematic switching behaviour in some devices.
      If you have constructive criticism please provide it in a civil manner, rather than just repeating insults thrown by Amir when you perhaps don’t understand the mechanisms yourself.

      Reply
      • Good point and I like your reviews. Another suggestion: how about showing frequency response in high precision like 10Hz to 25kHz with a range of +/-3dB in this and your future reviews? The filter plots with white noise and 100+dB of range cannot show things clearly.

        Reply

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