We hate to have to say it, but the headphone output circuitry fitted to a great many otherwise excellent hi-fi components often leaves a lot to be desired, so you should not necessarily rely on it to give you great sound. In some cases this is simply because of low output levels, in other situations because of a high output impedance. The obvious solution is a device that’s been specifically designed to drive headphones — a purpose-designed headphone amplifier.
The problem with this obvious solution is that high-quality headphone amplifiers are expensive — at least most are. A few, like the iFi Zen Can, are very reasonably priced. So reasonably priced, in fact, that they’re almost in impulse-purchase territory, particularly if there’s a sale on of some kind.
But can a reasonably-priced dedicated headphone amplifier deliver the goods that are required? Let’s see.
The iFi Zen Can is not only weirdly named, it’s also weirdly shaped, as you can see from the photograph above. But it’s a chassis shape iFi has used previously, and continues to use in other models, so it’s cost-effective. It’s also relatively compact, so you won’t need much space for it. (It occupies a space of around 16 x 3.5 x 12cm.)
Despite its compact dimensions, there’s a surprising amount of connectivity and control on this unit. On the front panel, starting from the left, there’s a power/standby button. Then there’s a button that cycles through the three rear inputs. We’ll look at them shortly. Next is a ‘Gain’ button. There are four levels of gain: OdB, 6dB, 12dB and 24dB. You can choose from those to allow you to set the next control, the knob which controls the traditional level setting, near to the 12-o’clock position, where potentiometers tend to be most accurate.
As you can see from the photograph, there are the two main output connections — a 6.35mm ‘phone socket for full-sized headphone plug designed to drive unbalanced headphones, and a 4.4mm Pentaconn TRRRS (Tip, Ring, Ring, Ring, Sleeve) socket for driving balanced headphones.
Around the back of the iFi Zen Can are three sets of inputs and one additional output. The inputs are stereo audio via RCA sockets, stereo audio via a 3.5mm socket, and balanced stereo audio via another 4.4mm Pentaconn socket. The output is also a balanced 4.4mm Pentaconn pass-through.
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But what is a ‘balanced’ headphone, and how is a balanced headphone design different from an unbalanced one?
In an ‘unbalanced’ headphone design, you have a ‘positive’ line for each channel and a single ‘negative’ line which is also ‘ground’ and which is shared between both stereo channels. In a balanced headphone design, the only thing that is shared between the two stereo channels is the ‘ground’ reference. Each channel has its own separate ‘positive’ and ‘negative’ connections.
Balanced headphones have been around for some few years, but when they were first introduced there was no standard connector for them, so manufacturers mostly re-purposed existing connectors, such as conventional phone plugs and sockets (either the standard 6.35mm stereo or the mini 2.5mm stereo types) or standard three-pin XLR plugs and sockets. The problem with using these connectors was that they didn’t provide sufficient discrete electrical connections, so two were required in order to connect a single set of headphones.
To complicate things even further, when it first introduced its true differential balanced headphone amplifiers, iFi actually recommended using 3.5mm TRRS connectors, which are the types used for gaming headsets with microphones built-in.
This was simply a mess, because two connectors were required when only one would have sufficed, and different manufacturers used different connector types, so various different adaptor cables were required depending on what type of headphones you wanted to plug into what type of component. So you needed multiple adaptors if you used the same pair of headphones with different components (say a home headphone amp and a portable one) or the same component with different types of balanced headphone.
This is where the so-called ‘Pentaconn’ plug (and socket) come in. It’s a relatively new (2015) connector type developed by a Japanese company called NDICS (Nippon Digital Information Communication Service). The name itself is derived from combining the Latin word ‘penta’ (from ‘pente’, the Greek word for ‘five’) with an abbreviation of the word ‘connector’, which is appropriate because there are, indeed, five connections made by a Pentaconn connector — Left Positive, Left Negative, Right Positive, Right Negative and Ground (usually abbreviated to L+, L-, R+, R-, G). It’s because all these connections are made using a single tubular connector with separate sections that are insulated from each other (see the pictured plug overleaf) that a Pentaconn plug is sometimes called a TRRRS connector. But another reason it’s often called a TRRRS connector is that we suspect that NDICS has trade-marked the word ‘Pentaconn’ in many markets, so that although it’s perfectly legal to manufacture and use TRRRS connectors, it would be illegal to refer to them by the name ‘Pentaconn.’ And, just in case you were wondering, we have absolutely no idea why the industry doesn’t refer to them as T3RS connectors, less clumsy than TRRRS in print, and far easier to pronounce.
But the T3RS/Pentaconn story doesn’t end here, because of course it’s possible to make the same type of connector in various different diameters, just as conventional ’phone plugs come in multiple diameters. Personally, we would like the 4.4mm diameter T3RS design to prevail (as used on the iFi Zen Can), because the plug size is sufficient to provide a contact surface area that’s adequate to provide a fail-safe high-quality electrical connection, while the plug and socket are sufficiently compact to be practical on portable players.
Obviously until things work themselves out (which may be never), adaptor cables will be required but over the past few months adaptor cables for 4.4mm TRRRS connections have transitioned from being obscure and unobtainable to being only kind-of obscure and somewhat available (with a bit of searching).
You might be wondering now whether balanced headphones are intrinsically different from unbalanced headphones. In fact, there’s no difference at all between balanced and unbalanced headphones other than the way the leads are connected to the driving elements (be they dynamic, planar, electrostatic or any other type). In theory, any headphones which use left and right plugs into the ear cups can be run balanced.
But back to the iFi Zen Can. iFi says that not all headphone amplifiers that have balanced headphone outputs are balanced all the way through, and that many “operate single-ended internally” (i.e. unbalanced). We don’t know how widespread this might be, but iFi says that its Zen Can employs a “fully-discrete and balanced amplifier audio circuit” in a “full symmetric dual-mono” configuration. Furthermore, it calls the design “Class-A Discrete” which, it says, “has come straight out of the iFi flagship headphone amplifier, the Pro iCan, which… is 11 times the price of the Zen Can.”
As for output voltage, the iFi Zen Can is rated at 15.1V into 600-ohm loads (385mW) and 11V into 64 ohms (1890mW) from the balanced output. Those are monstrously huge output levels… as are those from the 6.35mm headphone output: 7.6V (196mW) into 300 ohms, and 7.2V (1600mW) into 32 ohms.
iFi says the signal-to-noise ratio (SNR) is better than 120dBA balanced, and 118dBA single-ended, but it does reference the signal level to maximum outputs (15.2V and 7.6V), which in turn maximises the ratio. THD+N is stated at 0.0007% (balanced) and 0.006% (unbalanced) under output conditions which have no relation to each other.
All well-equipped hi-fi equipment reviewers (and audiophiles) will own multiple headphones including regular single-ended (that is, ordinary unbalanced) headphones and in-ear monitors (IEMs), several of which (Audiofly AF-180 Mk II, Focal Blear, Oppo PM3, Sennheiser HD 5608 and Sennheiser IE 300) were used in preparing this review.
For balanced headphone use, we used Sennheiser’s HD 6608 headphones. These come
There’s no difference at all between balanced and unbalanced headphones other than the way the leads are connected to the driving elements…
with a 3-metre cable with a regular single- ended 6.35mm plug on the end (a 6.35mm to 3.5mm adaptor is provided), plus another 3-metre cable with a 4.4mm TRRS plug on the end for balanced operation. At the headphone end, the left and right cables are terminated in what seems to be a proprietary two-pin Sennheiser connection. This meant that we could use the HD 6608 cable on a nearly quarter-century-old pair of Sennheiser HD 535 headphones, so we did try this out as well.
In operation, the iFi Zen Can runs pretty hot, but we guess that’s Class-A for you, exacerbated by the fact that there are no ventilation holes or slots in the casing, so the design appears to rely entirely on the casing itself radiating the heat. However, although we do think that it runs ‘pretty hot’ as we said in the previous sentence, it doesn’t run so hot that you will feel any discomfort if you place your palm on its top. (Unless, we guess, you have an abnormally sensitive palm!)
Your first consideration regarding the performance of any headphone amplifier should always be impedance matching. We were recently using a pair of Audiofly AF180 Mk2 in-ears with a high-ish end ($5k+) stereo amplifier with a headphone output with a rated output impedance of 40 ohms and judged their sound quality with this set-up as being rather poor. But we thought this poor sound quality may have been because these Audioflys are three-way balanced armature earphones with a low nominal impedance (16 ohms) that varies considerably across the audible frequencies.
So in order to check that the result was a result of an impedance mismatch, we plugged the Audioflys into the iFi Zen Can and played exactly the same tracks over again. Wow! They came to life and were now accurate, balanced, detailed and with everything sounding just right. When we plugged them back into the expensive amplifier, again the sound quality went south. Sure, headphones with a higher average impedance will be less subject to such an extreme effect but we would prefer that our headphone amplifier be a device that will work well with all headphones, not just a select few — or, indeed a specific pair.
We have been using the iFi Zen Can for a couple of months now, and with all the headphones and earphones we’ve tried with it, it has been a delight. It has been a delight in the sense that it does the audio version of becoming invisible in the reproduction chain. We simply didn’t hear it. What we heard was the individual characters of all the headphones and earphones we used — and they’re all different! — as they did their best to deliver music according to their various designers’ conceptions of high fidelity.
That was uniformly extremely revealing. For example, we have been puzzling for a while about why the 2013 remastered stereo version of Nina Simone’s debut album, ‘Little Girl Blue’, originally released back in 1958, sounds so damned good. One reason is obvious: they didn’t — couldn’t — do much in the way of dynamic compression back then. So there’s a very pleasing liveliness to the music that, in modern recordings, tends to be available only on audiophile jazz.
But there should be easily audible tape hiss. This is years before Ray Dolby invented his noise reduction system. So where’s the hiss? Clearly some digital signal processing has been applied to eliminate it. Yet even with very high resolution speakers, we had heard no evidence of such.
But as we are sitting here, streaming this album from Tidal (Mac Mini to Pro-Ject DAC, which is showing an MQA indicator, to the iFi Zen Can, to Focal Flear headphones), we can now hear, occasionally a slight confusion around the edges of notes as they fade to zero. And a tiny amount of hash around Simone’s voice where, presumably the algorithm had trouble distinguishing the tape hiss it was attempting to eliminate from the sound of her rich tones. These are the remnants of the noise reduction. It has been done very, very well and, as we said, it was a puzzle until this system revealed it to us.
Some more impressions: Jacob’s Ladder on Rush’s 1980 album ‘Permanent Waves’. The sound was very open. Yes, the instruments were arrayed through our head, rather than out in front. But the sense of air made that seem entirely unobjectionable.
We played with the buttons at the far right of the unit during this track. The effect of both buttons was surprisingly subtle.
The ‘3D’ button’s effect seemed to narrow the stereo image very slightly. It wasn’t objectionable, but we couldn’t see the point of iFi fitting it, or of us using it: it basically failed to justify its existence — at least in our opinion. You’re welcome to use it and draw your own conclusions.
That ‘XBass’ button, however, had us on the horns of a dilemma. It really does boost the bass noticeably but this doesn’t result in any lumpiness or any sense of artificiality. Instead, it just seemed to compensate for the bass roll-off of the various opened-backed headphones we used yet at the same time was not objectionable even when we were listening to a pair of Oppo headphones, which are essentially flat in their low-frequency output to an octave below 20Hz. And we found this to be true even when playing albums that had plentiful deep and extended bass, one excellent example of which is Billie Eilish’s When We All Fall Asleep, Where Do We Go’.
Our dilemma was that the audiophile’s mantra is: “Don’t mess with music.” In other words, ‘leave it pure!”. But the sound of that XBass circuit was so compelling we just had to use it to mess with the music, because it just sounded so good! So we left the XBass circuit on and played Max Reger’s delightful Maries
Wiegenlied from the analogue 1976 Swedish recording capture on the ‘Cantate Domino’ album. The soprano Marianne Melinas is accompanied only by pipe organ. Switching on the XBass circuit did just one thing: it enhanced the organ pedal notes noticeably, but left every other aspect of the sound quite untouched.
OK, so the XBass did draw attention to itself in Right Hand Man from the soundtrack of ‘Hamilton’, but that was the only time in our extensive listening sessions that it did, and even then, we thought that the extremely deep bass that was being enhanced ended up sounding more involving with the circuit than without it.
So to answer the question we posed at the start of this review: “Can a reasonably-priced dedicated headphone amplifier deliver the goods?”, this review proves that with the iFi Zen Can, it can.
IFI ZEN CAN HEA PHONE AMPLIFIER
Extraordinary value for money
High output, low output impedance
Useful bass-boost function
Frequency response: 20Hz- 20 kHz (-3dB) Max output (balanced) 6000: >15.1V/385mW
Max output (balanced) 320: >6.0V/1150mW
Max output (unbalanced) 6000: >7.6 V/98 mW
Max output (unbalanced) 320: >7.2 V/1600 mW
S/N ratio: >120dBA
Gain: OdB, 6dB, 12dB, 18dB Dimensions(whd): 158 x 117 x 35mm Weight: 515g