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Chord Electronics Mojo portable DAC/headphone amp

Chord Electronics Mojo portable DAC/headphone amp

While attending the first ever CanJam London event last fall at London’s Hotel Russell, I chanced to meet up with Chord Electronics Managing Director John Franks and with the firm’s consulting engineer and resident digital audio guru Rob Watts.

“Will you be able to attend the product roll out event we will be holding at the Shard in London this October,” asked Franks. I indicated I would try to attend, but that if I was unable to come over from the ‘States, then at least one of the members of the Hi-Fi+ UK team would be on hand.

Sensing that something good might be afoot, I asked, “Can you give me any hints as to what you’ll be announcing?”

“I can’t really say much at this time,” said Franks with practiced nonchalance, “except that it might be Chord Electronics’ most important new product announcement to date.” Given the characteristic penchant for British reserve, I took Franks’ meaning—if translated into American-speak—to be, “You don’t want to miss this one, because it’s going to be huge!”

I glanced over at Mr Watts, who had a certain glint in his eye and a subtle, Cheshire-cat-like grin on his face. “I can’t give any details away, but I promise you this one’s going to be a bit special,” which for a gentleman of Watts’ inherent English modesty is really saying something.

With curiosity piqued, I left the two men to finish their breakfast in peace, but as I walked away I remember thinking something of serious audiophile significance would likely be arriving from Chord headquarters at The Old Pump House in Maidstone. And Chord did not disappoint, since the then secret and now fully released product in question was none other than the firm’s remarkable new Mojo portable headphone amplifier/DAC, priced at £399 (US$599), and built in the UK.

To grasp the significance of the Mojo, it is necessary to turn back the calendar a few years to consider the impact of another breakthrough product from Chord: namely, the Hugo portable headphone amp/DAC, priced at £1,400 (or about US$2,495). Upon its inception, the Hugo won critical acclaim as perhaps the finest and most versatile portable headphone amp/DAC the audiophile world had ever seen or heard. For those serious about high-end headphones and top-flight sound quality, the Hugo became the device to have—the product that served (and still serves) as the standard against which other devices of its type would be compared. What is more, astute listeners soon discovered that not only was the Hugo a best-of-breed product, but that it also stood as one of the most sophisticated and accomplished high-end audio DACs then on the market, regardless of price or physical format.

 

But praiseworthy though the Hugo was and is, the device posed certain drawbacks and challenges. First, although portable, the Hugo was by no means pocket-sized (the Hugo is roughly the size of paperback book), meaning that it was not really an on-the-go device. Second, the Hugo was undeniably (and for some, prohibitively) expensive; the best is never cheap, but for obvious reasons, even the most ardent of headphonistas likely will think twice before dropping four-figure sums of money on a portable device. Third, the Hugo featured user controls that, although cleverly and attractively implemented, were sufficiently unorthodox so as to prove confusing, at least for some listeners.

What was needed, Chord reasoned, was a product that in virtually every way offered Hugo-like performance, but in a smaller and more ergonomically satisfying package, and at a dramatically lower price. That, in a nutshell, is precisely what the Mojo aims to be.

The Mojo is roughly the size of (or perhaps a bit smaller than) a deck of playing cards, so that when viewed alongside the original Hugo, the little Mojo seems positively Lilliputian (it’s about a third the size of its illustrious big brother). Its finely sculpted, black anodised aluminium chassis features subtle curves and gently scalloped recesses for three pleasingly dome-shaped control buttons: an on/off switch and a side-by-side pair of up/down volume controls. Adding an almost whimsical touch of colour, the three buttons illuminate from within; the hue of the power button indicates the sampling rate of the files in play, while the vibrant colours of the volume buttons give visual confirmation of the output level settings chosen. Most of all, though, the Mojo simply feels pleasing in the hand—much like a favourite talisman. This is very much by design. In fact, according to John Franks, the Mojo’s general shape and surface textures were inspired in part by the look and feel of the smooth beach pebbles his daughter likes to collect.

Before talking about the Mojo’s sound, let me first provide a summary of the unit’s basic features and functions, and also spend a bit of time discussing the sophisticated design philosophy that guided the Mojo’s development.

The Mojo provides four basic inputs: an optical digital input, a coaxial digital input, and two USB inputs (one for playback and the other for power charging). In turn, Mojo offers two variable level headphone outputs implemented via 3.5mm mini-jacks—the train of thought being that friends can thus share the Mojo listening experience if they so desire. Interestingly, the headphone outputs can, by following a Chord-specified start-up sequence, be configured as line-level outputs for those wishing to use the Mojo as a standalone DAC. Even so, my sense is that Chord expects most Mojos will be used primarily to drive headphones or earphones.

The DAC section of the Mojo supports PCM files from 32kHz to 768kHz and DSD files ranging from DSD64 to DSD256—capabilities that handily exceed those of the original Hugo, which supported PCM files at up to 384kHz and DSD files up to DSD128. As with the Hugo, the Mojo DAC’s interpolation filter is implemented via a Rob Watts-designed WTA filtering algorithm running on a computationally potent, but low power consumption FPGA (field programmable gate array) device—in this case, a Xilinx Artix 15T chip. According to designer Rob Watts, this powerful FPGA actually handles a number of functions for the Mojo including, “S/PDIF decoding, USB time, DPLL, WTA filtering, DSD decoding and filtering, volume control, thermal protection, battery status, noise shaping and DAC (functions).” The Mojo is compatible with iPhone, Android, or Windows smartphones and with Mac, PC, or Linux computers (though a Chord-supplied device driver will be needed for use in Windows environments).

Chord says that the, “Mojo shares Hugo platform FPGA code but with half the power consumption.” Indeed, the Xilinx Artix 15T device used in the Mojo is in principle more computationally powerful than the earlier-generation Xilinx FPGA used in the Hugo, but to accomplish Chord’s low power-consumption objective, the Mojo’s FGPA is deliberately run with its clock speed turned down (lower clock speed = lower power draw = lower operating temperature).

One critically important point is that the design of Chord’s Hugo and Mojo DAC sections are radically different to most other desktop or portable DACs on the market. The theories involved can get a bit complex (and frankly exceed the limits of my own technical knowledge base) so I will try to provide a simplified—but hopefully accurate—layman’s explanation. According to designer Rob Watts, certain fundamental aspects of digital audio sampling theory are either misunderstood or simply overlooked by most designers. Chief among these overlooked elements is the notion that—and please stick with me here—with digital audio files of CD resolution or better, it is always possible to fully and perfectly recreate the original analogue waveform provided you have digital filters of infinite (or virtually infinite) tap lengths. Ah, but there’s the rub.

Most off-the-shelf DAC chips provide perhaps a couple of hundred digital filter taps, which Watts says is not nearly enough to properly recreate certain crucial timing aspects of music. For this reason, Watts uses FPGA-based filters and his own WTA filter algorithm, which support tens of thousands of digital filter taps, leading to markedly better resolution of timing (that is, says Watts, “the starting and stopping of notes”). Chord does not directly specify the number of filter taps supported by the Mojo, though from conversations with Franks and Watts I suspect that the Mojo may actually offer more filter taps than the Hugo, but with the proviso that its FPGA clock speed is turned down to reduce power consumption. One difference between the Mojo and Hugo, however, is that the Mojo uses very subtly different filter parameters to achieve a sound thought to be friendlier to mid-priced headphones or earphones. In any event, the Mojo stands as one of the most sophisticated DACs that money can buy, despite its diminutive size.

 

Like the Hugo, the Mojo is designed with the thought that its sophisticated digital functions should be implemented through circuitry and firmware that consumes as little power as possible, while creating as little noise as possible. This approach leaves the lion’s share of the unit’s battery power available to drive Mojo’s very efficient, low noise, discrete analogue audio section. Chord specifies the Mojo’s maximum power output as 720mW @ 8 Ohms with THD of 0.00017%, which is more than adequate to drive today’s more demanding full-size headphones. The result is a tiny little portable amp/DAC that in every way sounds like a truly sophisticated, full-size desktop unit (or perhaps even better than that). Chord claims the Mojo provides, “state of the are 3μV output noise with 5V output voltage, (yielding) 125dB dynamic range.”

Unlike some competing portable headphone amp/DACs, neither the Hugo nor the Mojo provides (or requires) master gain adjustment switches so as to accommodate sensitivity differences between power-hungry full size headphones and ultra easy-to-drive CIEMs. Chord’s staunch position is that, when DAC and analogue circuitry are appropriately low in noise, gain switches not only are not necessary, but also are potentially detrimental to sound quality. To put that claim to the test, I listened to the Mojo through my HiFiMAN HE 1000 and Edition X full-size headphones and through my Noble Audio 4S and Westone ES60 custom-fit in-ear monitors. I also did regular comparisons between the Mojo and the Chord Hugo that I use as my portable amp/DAC reference. In every instance, the Mojo had more than ample power for the full-size headphones, yet was so quiet that it proved absolutely enchanting when used with my CIEMs.

Now we’ve come to the point where we can focus on the aspect of the Mojo we care about most: namely, its sound. If I had to summarise the Mojo’s sound with just three descriptors, the three I would choose are these: natural, organic, and authoritative. Let’s talk about each in turn.

When I say the Mojo sounds natural, I mean that it renders musical timbres, textures, and transient sounds in a wonderfully believable and unforced way. As you listen, there is less a sense of being in the presence of bowls-you-over grade ‘great hi-fi’ and more a sense of effortless connection with the real-world sounds of human and instrumental voices. In short, the Mojo invites listeners to focus less on the constituent elements of sounds and more on the overarching whole. Note that this does not imply any sort of lack of transient or harmonic information, since the Mojo does a terrific job on both counts. Rather, it is more a matter of proportion and balance; instruments and voices simply sound like themselves, without any artificial spotlighting or underscoring of their sounds merely for ‘dramatic effect’. It’s the sort of quality you might not notice in the first 30 seconds of listening, but after enjoying a track (or album) or two one gradually becomes aware that virtually every piece of musical material the Mojo touches seems to come out sounding spot on.

This quality became most apparent to me in listening to pianist Alfred Brendel’s performance of Mozart’s Fantasia in C minor [Mozart: Favourite Works for Piano, Philips]. One of Brendel’s great gifts—especially for this music—is that his performances typically are less about pianistic flash and pyrotechnics, and more about subtlety, fluidity, and masterful touch. The Mojo played right into this schema as it, too, is capable of revealing (but never overplaying) almost infinitesimal shifts in phrasing, dynamics, and—here’s that word again—touch. When you listen through a Mojo, you can’t help but sense that you and your music are in good hands.

The Mojo’s organic quality focuses specifically on the timbres and distinctive attack and decay characteristics that are the defining ‘signatures’ of the instruments we enjoy hearing. To borrow a term from contemporary architectural discussions, I found the Mojo handily reveals the ‘materiality’ of the instruments in play. Thus, acoustic basses sound realistically large and ‘woody’, trumpets sound incisively articulate and ‘brassy’, tubular bells sound, well, believably tubular and ‘metallic’, and so forth. These might seem like perfectly ordinary things that all DACs and amps should do, but in my experience they are not as simple or ordinary as you might think. The difference I mean to point out involves the quality of authenticity; many DAC/amps can give you a fair simulacrum of the real thing, but the Mojo (like the Hugo before it) steps things up several notches in terms of realism, believability, and timbral accuracy.

One track that brought this organic quality home for me was the title song “Gaucho” from Steely Dan’s album of the same name [Gaucho, Geffen 24/192]. The track at one point features a stunningly beautiful sax solo, and through the Mojo I found I could fairly sense the shimmer of the horn, the touch of the performer’s fingers on its pads, and the distinctive and expressive rasp of its reed. I wasn’t hearing a simulation of a horn, but rather something much more like a real horn in play.

Finally, the Mojo sounds authoritative, by which I mean that it figuratively grasps music (any kind of music) by the scruff of the neck, gives it a good shake, and then breathes life into the performances at hand. This holds true even on powerful and at times raucous rock material played at considerable volume. A perfect example would be the track “We Are Finding Who We Are” from King’s X’s Faith Hope Love [Metal Blade]. Bassist/vocalist Doug Pinnick’s thunderous yet articulate bass lines and penetrating lyrics have been known to overwhelm lesser portable amp/DACs but the Mojo took them in stride with casual, confident ease. That last quality—the ability to handle potentially difficult passages with palpable ease—is what the Mojo’s authoritative sound is all about.

 

How does the Mojo compare to the Hugo? My answer is that the family resemblance between the two is unmistakable, but that the products do not by any means sound ‘identical’ or interchangeable. Stated simply, the Mojo offers a very slightly warmer and ever so slightly less forward-sounding presentation, with almost—but not quite—the same high levels of resolution as the Hugo. For a great many headphones and earphones, this is terrific combination of virtues. With that said, when listening though highly revealing top-tier transducers (for example, the HiFiMAN HE 1000 or the Noble Audio 4S CIEMs), there is no denying that the Hugo offers greater resolution and, arguably, more perfectly neutral voicing overall (the perceived voicing differences are, as noted above, likely attributable to the slightly different filter parameters used in the Mojo). For all-day/everyday listening, the Mojo makes a very fine choice, but when you are in the mood to push performance limits the Hugo will be the device of choice. Of course, the ideal solution would be to own both.

Are there any drawbacks to the Mojo? Personally, I can’t think of any, though I am aware that some journalists have commented about the Mojo ‘running hot’. Candidly, I find this much ado about nothing. I’ve used my Mojo review sample with all kinds of headphones for hours on end (and at a wide range of volume levels) without it ever becoming more than mildly warm. I suppose if you wrapped the Mojo up in insulation, ran it under the noonday sun in Phoenix, AZ, and tried playing music while simultaneously trying to charge the unit, you could conceivably get it to overheat and shut down. But for the most part, Chord has done its power dissipation homework, keeping the Mojo’s operating temperatures well within sensible bounds.

In summary, the Chord Mojo is a marvel both of sound-quality-first design and cost-effective engineering. It is one of the finest and most capable portable amp/DACs I have yet heard regardless of price, and one whose value for money quotient is clear off the charts. If you have always craved a top-tier product of this type, but thought you could never afford one, the Mojo is now officially your ticket to ride.

Technical Specifications

Type: High-resolution portable headphone amplifier/DAC

Digital inputs: One TOSLink optical input (1compatible with 192kHz PCM and DSD64 via DoP), One coaxial S/PDIF input (compatible with 384kHz PCM – 768kHz PCM (special option) and DSD64/128 via DoP), and One USB input (compatible with 768kHz PCM and DSD64/128/256 via DoP; requires a Chord-supplied device driver for Windows environments)

Analogue outputs: Two 3.5mm headphone jacks (can be reconfigured as fixed, line-level outputs)

Device drivers: Mac OS/iOS/Android – No driver required. Windows: Chord-supplied device driver required

Digital Filters: Very long tap-length digital filters implemented via Xilinx Artic 15T FPGA running a proprietary Rob Watts-designed WTA filter algorithm

Controls: Power on/off, Up/Down volume control; switches also can be used to control intensity of display lights and to configure Mojo for use as a standalone DAC with fixed line-level outputs

Battery: Sufficient power at full charge for approximately 10 hours of operation

Power Output @ 1kHz: 600 Ohms, 35mW, 8 Ohms, 720mW

Distortion – 1kHz 3V output: 0.00017% THD

Dynamic Range: 125dB

Output Impedance: 0.075 Ohms

Accessories: USB-A-to-USB-Mini-A digital and/or charging cable

Dimensions (H × W × D): 22 × 62 × 82mm

Weight: Not specified

Price: £399

Manufactured by: Chord Electronics Ltd

URL: www.chordelectronics.co.uk

Tel: +44 (0) 1622 721444

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