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CHORD MOJO PORTABLE DAC / HEADPHONE AMPLIFIER REVIEW
 

CHORD MOJO

 

 

Chord's Mojo DAC / headphone amplifier, reviewed by Noel Keywood.


Announced at a Chord press conference in London, 14th October, 2015, Mojo is a new portable digital-to-analogue convertor (DAC) with volume control and headphone outputs, intended as an audio upgrade for mobile phones.
    After unexpected success with Hugo, a small £1000 portable DAC for use in the home, Chord told us that Mojo is even smaller and aimed at those on the move. The surprising news is Mojo costs just £399 – way below any other Chord DAC. And yet it uses their own, unique Watts Transient Aligned DAC technology that offers results few companies – globally – can match. 
    Mojo isn't simply Hugo crammed into a smaller case however. It uses a 26000-tap digital filter to reduce quantisation noise to negligible levels, where commercial DAC chips use 20 taps or so, designer Rob Watts told me. Mojo also has fully automatic input sensing and switching, making it digitally agnostic. Whatever you put in, it sees it, understands it and converts it to analogue automatically.
    Mojo can process conventional digital (PCM) up to 32bit resolution and 786kHz sample rate, way above current digital music file specifications. It can also sense and read DSD (Direct Stream Digital) running up to 4x the original data rate used on SACD – quad DSD as it is termed. This means it has massive processing power; most DACs only just manage the data rate needed to process  double rate DSD and 384kHz sample rate PCM, so Mojo is twice as fast as its hottest rivals.



    Yet Mojo is small, pocketable and battery powered. A light, soft-shell Li-polymer battery provides 8-10 hours use, from a 4 hour charge (if completely discharged) USB phone charger. With a depth of 21mm, Mojo is a bit large for a shirt pocket, but height and width dimensions of 61mm and 83mm make it an easy fit in a trouser pocket. Surprisingly, Chord do not use a light, durable moulded plastic case, but a bullet-proof machined alloy case like that of their other products. It has a sombre dark brown/grey finish that is scratch proof, they claim.  Mojo weighed 173gms on our scales – anything over 150gms is relatively heavy for portable use and Mojo feels 'solid'.
    Controls are few: just three hemispherical illuminated buttons. There's an on/off switch that changes colour to show digital sample rate, plus up and down volume buttons that change colour to show volume level. Just as well because Mojo produces a massive 4.3V output our measurements showed, enough to sound shatteringly loud. This figure is comfortably above most hi-fi portable Digital Audio Players (DAPs), that top out at 3V. On occasion it did accidentally blast my Oppo PM1 Planar Magnetic headphones as a result, so the colours of the volume buttons are worth watching. Chord use green to indicate comfortable listening level, and light blue as loud, whilst very loud is dark blue and there are various other blue-purple spectrum hues to warn of shattering – if your ears don't do so first.


There are USB and S/PDIF (Coax, Opt) digital inputs. The former uses a microUSB socket and would typically connect to a Samsung phone through a microUSB-to-microUSB cable, that fits their curious dual-socket. An iPhone needs a Lightning-to-microUSB adaptor (£15, $20) with a microUSB cable, or a Lightning-to-microUSB cable. Under test I ran Mojo mostly from my Astell&Kern AK120 digital audio player acting as a transport, connected via Mojo's OPTical S/PDIF input. There's an electrical S/PDIF input too (COAX), through a small 3.5mm jack socket.
    Importantly, Chord do not use the signal-transfer USB for charging. Instead they fit another microUSB solely as a charger input, allowing Mojo to be run and/or charged from an external USB charger/power supply. That can take the form of a phone charger, but I used a smoothed 5V USB power supply unit (£20 from Maplins) for reduced noise.
    There is no analogue audio input, nor Bluetooth for a cord-free link to a phone, or hi-fi as Astell&Kern use. Whilst Bluetooth limits quality to CD standard, it is convenient for mobile use. Instead Mojo must be connected to both phone and headphones through cables, so taking a call is difficult. It's common to use a stout rubber band to hold a DAC to a phone; Chord have machined in narrow grooves at each end of the case for this.
    Under test, the optical input worked to 192kHz from our spectrum analyser, only occasionally becoming intermittent, but 192kHz music files did not play at all from my Astell&Kern AK120 over Chord's own short optical cable. This behaviour is common via optical S/PDIF because the cables and TOSLINK connectors cannot reliably support the data rate 192k imposes. It isn't a Mojo problem.

   Mojo can be used in a hi-fi system as a CD player upgrade, or as a digital preamp; I tried both. As a CD player upgrade it should be turned on with both volume buttons pressed, then instead of remembering the last volume setting, Mojo sets output to CD level of 2V, both buttons lighting blue. The digital output of a CD player is connected to either Coax or Optical S/PDIF input, and a headphone output taken to the hi-fi through a 3.5mm-to-phono adaptor lead. This worked well and offered interesting sonic result – see Sound Quality.
    Another way to use Mojo is to drive power amplifiers direct. It drove a pair of Quad Elite QMP monoblock power amplifiers perfectly. With 4V output Mojo has plenty of headroom. There were no crashes or bangs at switch on or off.
    Chord claim you can run loudspeakers with Mojo (in theory at least it delivers 4W) so we hooked up a pair of massive Tannoy Westminster Royal GRs and it did indeed drive them to a respectable level! Best not to take loudspeaker drive seriously however; trying to drive heavy transient currents into 4 Ohms is not realistic from an internal  battery supply, nor with a charger connected since the output devices would likely overheat and/or current limit/shut down. It's a party trick  – no more.
    And of course Mojo can act as a high quality external DAC/headphone amp for a computer, connected via its USB output, or with Macs via optical for those having an output in the headphone socket. All this highlights the flexibility of Mojo and how it can be used in a hi-fi system, or computer system.
   Mojo's  'Watts Transient Aligned' (WTA)  DAC is unique to Chord and has been under steady development by Rob Watts over decades.   Mojo gets its latest iteration – full strength, not in cut-down form.
    At the press reception Rob told me its digital architecture, and especially the use of a 26000-tap digital filter, allow almost compete elimination of digital noise, which has a repetitive pattern upsetting to the ear. Our measurements show it just managed 125dB as claimed. But what does this figure mean?
    Top quality hi-fi DACs manage around 120dB within a consumer product, our measurements show, with a few exceptions like the Resonessence Invicta Mirus and Wadia di122 both of which exceed 130dB – and cost thousands. So for £399 Mojo is amongst the best, performance wise. When you add to this the fact that it doesn't need a mains supply, its advantages come into focus.


SOUND QUALITY
I ran Mojo from battery and a mains power supply – and there was little difference in its sound between the two. But then intermediary circuitry and internal charge-pumps would likely negate the influence of an external power supply.
    Headphones used were Oppo PM1 Planar Magnetics, and Philips Fidelio X1s – and immediately I noticed the Oppos sounded brighter and more vivid than usual; they commonly sound a little dull up top and lacklustre with small portable players, if not with mains powered headphone amps. like the Audiolab M-DAC I often use to drive them. Mojo cranked the PM1s up to the livelier nature of Philips X1s, yet at the same time it suppressed the slightly boomy bass of the X1s, pulling them into line too. Mojo had a calming and civilising influence on my headphones!
    With representative Rock tracks from Fleetwood Mac's Rumours album (24/96), Mojo had a fuller, more fleshed out sound stage than all players I have heard to date. Musicians were placed in a big and open space that seemingly extended beyond the ear pieces of my Philips Fidelio X1s. There was air and space around instruments and, after a short acclimatisation period, I began to realise that Mojo has extraordinarily powerful bass, that also runs very deep. It came over as altogether larger than my Astell&Kern AK120 portable player that in itself is punchy and fast in its sound, if with a more mechanical delivery.
    Mojo's treble was both strong and obvious, yet very sweet in Go Your Own Way, whilst rendition of detail was utterly superb – quite beyond that from all players I've used to date. Cymbals on Mick Fleetwood's drum kit rang sonorously and I could hear the quality of the skins on his drums. Strummed guitar sounded fine and delicate in the gentle yet vivacious way its strings were delineated, one from another. A synth line floated away on its own, whilst Stevie Nick's vocals hovered in front of me. Sudden drum strikes and cymbal crashes had great dynamic impact but perfect timing too; there was no slur – or seen the other way around Mojo gets time domain definition from digital right whilst all others sound hazy by way of contrast – as Rob Watts claims. I felt I was getting an education here.
    The complex guitar picking in Never Going Back I had never latched onto before, but with Mojo I was gripped, as I was by Lindsey Buckingham's gently implied vocals that sprang out of a dark background. And especially intriguing was the end guitar sequence that came over with a sweet clarity, yet amazing grip on timing that – again – I've never heard from any other source.
    Mick Fleetwood's kick drum put shuddering bass through my Oppo PM1 headphones on Go Your Own Way, imposing a grip at low frequencies that was extraordinary. Mojo has massive bass power (working from battery alone) that re-defines what a portable can do. This is down to the headphone amps, that Chord have engineered to conspicuous perfection it seems. The PM1s occasionally went subterranean with Pink Floyd's Time.
    Playing Radio GaGa from Queen (24/88.2) and more of their hi-def transcriptions again showed Mojo is different. I have played these recordings often through a large number of digital audio players in for review and mentally catalogued the tracks as sonically un-engaging, even though Queen's performances were exciting in real life. Mojo changed my view immediately; Queen tracks suddenly came alive through Mojo. Radio GaGa was powerful and punchy, and as gripping as you'd ever want. I had fun listening to the way Freddie Mercury managed to deliver this little ditty with strength and conviction. Mojo engaged me with the song and the performance.

 

 


Slotted into a hi-fi as a hi-res digital source, fed by an Astell&Kern AK100 portable and feeding Quad Elite QMP monoblock power amplifiers and various loudspeakers under review, Mojo had some treble prominence. If anything it sounded lean, but analytically detailed. It is balanced for headphones, especially those with strong bass like my Oppo PM-1s. Against our mains powered Oppo BDP-105D universal hi-res player, however, treble was more obvious. Brightly balanced loudspeakers or headphones may not suit Mojo; I'm afraid you'll need Dave and deeper pockets!

 

CONCLUSION
    Technologically, Mojo is all but untouchable. Whilst there are other DACs with better figures, they are all mains powered and cost around ten times more. Most portable audio DACs fall well below Mojo: they are a whole step down in quality. That positions Mojo in the current market. It's quite a place to be.
    With fabulous sound quality – big, open and powerful – plus the ability to control and drive even the most difficult Planar Magnetic headphones, Mojo is a DAC that sweeps the floor with all else. And you can use it in your hi-fi system too, or even drive Tannoy Westminster Royal GR loudspeakers with it – as we did!
    This isn't a DAC you can miss.NK

 

(see full review in forthcoming January 2016 edition of Hi-Fi World, out 1st December 2015)


CHORD ELECTRONICS MOJO    £399

 

Fabulous sound, great build quality and big illuminated buttons that change colour make Mojo unmissable – as does its low price of £399. A wonderful portable DAC and headphone amplifier.


FOR
- sound quality
- portability
- fully automatic
- quad-DSD replay
- up to 32/786kHz PCM digital
- works from mains power supply

AGAINST
- no Bluetooth
- sombre appearance
- no means of attachment to phone

- 192k via optical input not assured


Chord Electronics Ltd
 +44 (0)1622 721444
www.chordelectronics.co.uk


Rohde&Schwarz UPV audio analyser, used for all measurements.

 

MEASURED PERFORMANCE
    With volume set to give full output, whilst avoiding overload from a full level digital signal (0dB), Dynamic Range (EIAJ) measured a high 124dB, and with one small step up in volume of 1dB it hit Chord's claimed 125dB, as shown in our analysis. So Chord's figure is achievable without overload being obvious. Interestingly, turning volume up to maximum with the low level -60dB test signal gave 143dB Dynamic Range and this shows the potential of Chord's DAC. These are impressive figures: most hi-fi DACs achieve 120dB, a few expensive ones costing thousands 130dB. Portable DACs and DAPs usually measure around 115dB.
    Distortion was minimal, measuring a very low 0.014% as shown in our analysis. Again, this was with volume set to avoid output overload with a full level (0dB) digital signal. No distortion components are visible in our analysis, so 'distortion' here is noise, even though a narrow band harmonic-only analysis was used. Turning volume up to maximum to lift DAC output above subsequent amplifier noise returned 0.0017%, showing the potential of Mojo in this area.
    Frequency response measured flat to 31kHz (-1dB) via the analogue headphone output, output falling away steadily above this frequency to the upper theoretical limit of 96kHz from the 192kHz sample rate test signal.
    Mojo produced a massive 4.3V from its headphone outputs at full volume – more than enough to drive insensitive headphones, or power amplifiers direct. It can even drive loudspeakers. Chord quote 4 Ohm - 800 Ohm loads as being compatible, and output impedance 0.045 Ohms.
    Mojo delivered better performance figures under test than mains powered hi-fi DACs costing considerably more. It possesses outstanding measured performance. NK


Frequency response (-1dB)    4Hz-31kHz
Distortion (%)    24bit
0dB                                                  0.003
-60dB                                               0.014
Separation (1kHz)                           110dB
Noise (IEC A)                                -124dB
Dynamic range  (EIAJ)                   125dB
Output                                               4.3V

 

FREQUENCY RESPONSE, 192kHz sample rate.

 

DISTORTION, -60dB, 24bit.

 

DYNAMIC RANGE  125dB  (64.654+60).

 

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