Qables iQube V1 Headphone Amp & iQube V2 Headphone Amp/DAC (Playback 38)

Headphone amps and amp/DACs
Qables iCube V1,
Qables iQube V2
Qables iQube V1 Headphone Amp & iQube V2 Headphone Amp/DAC (Playback 38)

The Dutch firm Qables isn’t exactly a household word in the U.S., but based on my recent experiences I would company’s iQube V1 headphone amp ($549) and V2 amp/DAC ($699) should help establish the company’s reputation the U.S. in a positive. Let me provide some basic background information on the V1 and V2 to help you gauge whether either of the products might be of interest to you.

The iQube V1 is a very high-quality, portable class D headphone amplifier whose batteries are designed to be charged via a USB cable. Thus, the working assumption is that you will likely travel with a laptop (or a phone that uses a USB-type charger), and that you would prefer not lug around a separate wall-wart type charger just for the amp. Controls and inputs for the amp are simple but effective. On the front panel you’ll find switches for amplifier gain (high or low), amplifier on/off, a control knob for the very high quality Alps volume control, and two pilot lights (one for power on, one to show when the unit is hooked up to a USB power source for charging). On the rear panel, you’ll find a pair of mini-jacks (one for analog input signals, the other for the headphone outputs).

The entire amp is only a bit larger than a deck of playing cards. What words can’t adequately express is how nicely made the iQube V1 really is, sporting a matte silver finish with soft-feel black trim that, to me, seems highly reminiscent of the overall vibe of an old-school Leica camera from Germany.

The iQube V2, in turn, is a slightly larger portable product that combines the V1’s amp section coupled with an onboard USB DAC. Like the V1, the V2 is designed so that it not only receives digital audio data via a USB cable, but also uses USB as its charging source. The beauty of this arrangement is that the V2 meets the following core requirements:

•USB data interface for those times when you listen to digital audio files from your laptop or PC.
•USB power connections, which are very convenient (at least as compared to a wall-wart type charger/power supply).
•A high-quality onboard DAC with a low-jitter USB interface.
•Battery power to handle those situations where you cannot, or do not want to, connect the amp to a USB power/data source.
•An analog input for those times when you listen to music stored on an iPod/iPhone or other personal digital music player.
•A high-quality, high-efficiency amp to power just about any type of headphone you might care to bring on the road with you.
In this review, I’ll focus primarily on the iQube V2, since my comments on the V2’s amplifier section will also serve to describe the identical amplifier section of the V1. As you’ll see in a moment, both products have much to offer in terms of sound quality.


Consider this headphone amp/DAC if: you want a beautifully made amp/DAC (or amp only, in the V1’s case) that has found a way to tread that oh-so-fine sonic line between sounding open, airy, and revealing, on the one hand, but natural, full-bodied, and downright gutsy on the other. Also choose the V1 or V2 if you like the idea of portable products that use USB ports as their charging sources.

Look elsewhere if: in the case of the V2, you seek a DAC that can accommodate higher-than-CD-resolution data files (the V2 only accepts digital audio files with up to 16-bit/48 kHz resolution levels, but not higher). But note: on CD-resolution material, the V2 actually sounds better than may higher resolution DAC/Amps we have heard. Finally, look further if you are on a tight budget as the iQube units, which use very high-quality but also quite costly internal parts, are relatively expensive).

Ratings (compared to similarly-priced headphone amp/DACs):

•Tonal Balance: 9
•Clarity: 9
•Dynamics: 9.5
•Flexibility: 7 (doesn’t support high-res data files)
•Value: 8.5


While both iQubes may look simple on the outside, Qables has incorporated very high-quality parts in all the right places on the inside. Highlights (as shown on a manufacturer-supplied features list) include:

•Medical-grade double-layer epoxy circuit boards using HOFC (High Oxygen Free Copper).
•Circuit board designs optimized to enhances signal quality.
•Alps potentiometer.
•Vishay series 036 decoupling capacitors throughout.
•Panasonic stack film capacitors.
•Carbon signal resistors.
•Lumberg I/O connectors.
•Fully RoHS compliant design.
•CNC machined aluminum casing, with rubber touch/feel painted covers.
Apart from the construction highlights listed above, the iQube V1/V2 design also incorporates:
•A high efficiency (90-95%) Class D amplifier.
•(V2 only) A built-in USB receiver and separate DAC
•(V2 only) Tentlabs ultra low jitter clock generator.
•A built-in set of 4x AAA rechargeable batteries (non-user replaceable).
•An 8-fold output buffer for a (near to) load independent output behavior.
•A 4th order feedback loop for minimum distortion.
•A fixed, phase-shifted carrier wave oscillator said to decrease inter-channel distortion.
•An ultra low noise front end that accepts any line level source without the need for impedance matching.
Included accessories, iQube V1:
•4 rechargeable batteries, factory installed.
•Rubber elastic strap.
•Standard mini-jack to mini-jack cable/
•Metal box with padded interior (looks something like a Euro-spec “cookie tin”)
Included accessories, iQube V2, are as above, but adds:
•Velcro/elastic strap
•Custom Mini-USB/charging cable.


For this review we did much of our listening through three very revealing custom-fit in-ear monitors: the JH Audio JH16 Pro, the Sensaphonics 2MAX, and the Westone ES5. Other amps and amp/DACs used for comparison included the CEntrance DACport and the ALO Audio Rx MkI and MkII headphone amplifiers.


iQube Amp: as I suggested earlier, the iQube’s class D amplifier section combines, in roughly equal proportions, a good measure of openness and transparency on the one hand, with a robust, hearty, and full-bodied quality on the other. It’s a winning combination that works well for almost all types of music.

Bass is a notable strong point, with good extension and weight, plus excellent pitch definition. Many amps that claim to deliver this level of control do so at the expense of sounding almost over-controlled and thus bit thin and anemic. But not so, the iQube; it gets the balance of low frequency power and control just right.

Next, the midrange of the iQube likewise sounds well balanced, well defined, and extremely articulate. You’ll appreciate these qualities whenever listening to densely layered material where there are multiple musical threads to be delineated at once. There is real synergy between the low end and midrange of this amp, so that two broad frequency bands seem almost to collaborate, giving the amp a sound that is rich and expressive, but never overblown or in any way given to lush, syrupy-sounding colorations.

Finally, the iQube’s highs sound consistently well extended and revealing, though they can also sound just slightly “dry” at times. On one hand, you’ll hear plenty of treble transient speed and detail, with fine overall tonal balance, all of which contributes to the greater good. On the other hand, you may occasionally hear—at least through highly revealing transducers such as the in-ear monitors used for this test—faint traces of a slightly dry or perhaps slightly mechanical-sounding quality way up high. Note, however, that this isn’t a matter of outright brightness (in fact, far from it) but rather is a matter of a very subtle textural quality that some earphones reveal, but others do not.

In many respects, one could argue that the sound of the iQube amp is what really gives this product its appeal (for which reason some might find the less expensive amp-only iQube V1 preferable to the more costly iQube V2 amp/DAC).

iQube DAC: Not surprisingly the voicing of the iQube DAC section is similar to that of the iQube amp, including both acknowledged strengths and occasional weaknesses. Although the DAC accept data streams up to 16/48 (but not higher), I found that on the whole the DAC sounds better, as in clearer and generally better balanced, than some of the higher res DACs that I’ve tried. The point, here, is not to dismiss this DAC out of hand simply because it doesn’t handle 24/96 (or even 24/192) files—unless, of course, you already own or plan to acquire a large collection of high res material.

I do think that the DAC, more so than the iQube amp, bears the lion’s share of the responsibility for those periodic touches of treble dryness I mentioned above. On a positive note, the iQube’s highs sound at least as detailed and well defined as those of most competing DACs, but at the downside expense of sometimes exhibiting that dry quality which tends (albeit in a very subtle way) to make high frequency content sound just slightly artificial. These performance tradeoffs becomes especially apparent if you listen to well-made acoustic recordings made in relatively reverberant spaces, where the iQube will show you most of the high frequency “air” surrounding instruments and voices, but with a presentation that at times makes natural echoes and reverberations sound more like well-done (but ultimately artificial) electronic reverb effects.


To hear the fine, rich, and expressive qualities of which the iQube V2 is capable, try listening to the title track of Chris Jones’ Roadhouses & Automobiles [Stockfisch]. This well-recorded track highlights Chris Jones’ dark, richly textured voice and intricate guitar work, but also supports Jones with the powerful, soaring growl of Hans-Jörg Maucksch’s fretless electric bass, plus a handful of other supporting instruments.

Jones’ guitar sounds terrific through the iQube, so that the filigreed twists and turns of individual notes and arpeggios are given just the right emphasis—with the amp/DAC contributing a sound that is very clear, but never sterile. The iQube also does a great job of balancing the body sounds and higher harmonics of both Jones’ voice and of his guitar, so that you’ll hear a beautiful and appropriately weighted combination of body sounds and higher-pitched transient and harmonic sounds, with plenty of articulation and definition throughout.

Interestingly, the song features Jones supplying overdubbed backing vocals of his own, but with some supplementary contributions from other singers at specific points. The detail and definition levels of the iQube are sufficiently good that you can tell in an instant whether vocal harmonies are supplied by Jones, by the alternate singer, or—in some cases—both.

Similarly, the iQube nails the almost vocal growl and snarl of Maucksch’s fretless bass guitar, whose sound, I have found, is not necessarily easy to reproduce. Many amps have at least some trouble with this recording, because the lower register of Jones' voice overlaps with the range of the fretless bass, which can be a recipe for muddled low-end performance. But not so with the iQube; it makes child’s play of disentangling and delineating the overlapping voices, while convey the deep throb and weighty punch of the lowest bass guitar notes.

But to see what I meant by my comments to the effect that the treble region of the amp/DAC can at times sound slightly dry, put on the excerpt from the Paul Goodwin/Minnesota Orchestra/Minnesota Chorale performance of Tavener’s Icons of Eros as captured on the Reference Recordings 30th Anniversary Sampler. The piece is cleverly constructed so that it presents jaunty, almost dance-time sections as performed by strings and percussion, which alternate with much slower paced choral/string passages offered up with low percussion accents. The challenge, however, is that there are moments of silence between the alternating sections where you can hear the sounds of the previous passage slowly echo and then fade to silence within the highly reverberant recording space.

During these reverberation-filled moments of silence you get the opportunity to experience the iQube amp/DAC’s handling of low-level treble information as heard in isolation from the rest of the music. When this happens, I found that the echoes and reverberations, which can and should sound highly realistic through the best amp/DACs, tended to sound a slightly dry and artificial through the iQube V2—almost as if I were listening to sounds created by a good synthesizer rather the sound of live instruments in a natural recording space. As I noted above, however, some headphones make this quality of treble dryness more apparent than others, while some do not show it at all.


With an eye toward helping readers place the iQube V1 and V2 versus likely competitors I will make two comparisons, one showing the iQube V1 amp vs. the new ALO Audio Rx MkII headphone amp, and the other showing the iQube V2 vs. the CEntrance DAC Port amp/USB DAC.

iQube V1 vs. ALO Audio Rx MkII headphone amp ($399-$449)

•The iQube V1 costs between $100 and $150 more than the ALO Rx MkII.
•The iQube uses class D amplifier technology whereas the ALO is a conventional linear amplifier.
•Both amps uses very high quality parts, though the iQube arguably pushes the “parts quality envelope” even harder than the ALO does.
•The iQube uses USB ports as its charging source, whereas the ALO uses a conventional wall-wart type power supply. That said, however, the ALO sports a stout Lithium-ion battery pack that gives excellent playing time per charge, plus a cleverly conceived charging circuit that is said to promote long battery life.
•Both amps offer simply and comparably effective controls, though the ALO’s controls are generally more clearly labeled (the iQube uses symbols rather than words for switch and I/O jack labels, which look cool but may not offer the last word in clarity).
•Amp sections compared: the ALO offers levels of heartiness and richness comparable to those offered by the iQube, but with a greater emphasis on what might be called a smooth, “liquid sound.” The ALO’s highs sound lovely and are never mechanical sounding, though they are arguably not the last word in definition, articulation, or extension. By comparison, the iQube shows greater definition overall, a somewhat greater ability to delineate (or separate) individual musical lines, and more extended highs. But, as noted before, the prices of these positive qualities can be a subtle tendency toward treble dryness (though one that is much less obvious when using the iQube V1 or V2’s analog audio inputs rather than using the V2’s USB DAC input).

iQube V2 amp/DAC vs. CEntrance DAC Port ($399.95)

•The iQube V2 sells for a whopping $300 more than the CEntrance DAC Port.
•The iQube V2 amp section uses class D technology, whereas the CEntrance DAC Port provides a USB-powered pure class A amplifier.
•Very significantly, the iQube V2 is a portable device whose onboard batteries can be charged via a USB port. By comparison, the CEntrance DAC Port is not battery-powered and therefore is not designed for standalone use. In short, the DAC Port must be plugged into a USB port whenever it is powered up. Also significantly, the iQube V2 provides both analog audio and USB DAC inputs, where the DAC Port provides USB DAC inputs only. Together, these two factors make the iQube V2 usable in a number of contexts (for example, as a standalone amp for use with an iPod) where the DAC Port is unable to play.
•The iQube V2 DAC supports digital audio data streams at resolutions up to 16/48, while the DAC Port can handle data streams at up to 24/96 resolutions through both USB 1.0 and 2.0 ports.
•Both DAC sections feature solid jitter reduction technologies.
•Amp sections compared: the iQube amp offers a somewhat richer and more full-bodied sound than the DAC Port, but with touches of treble dryness. In contrast, the DAC Port amp is equally well controlled but more lightly balanced down low, but exhibits almost crystalline purity and sheer realism up high. The iQube sounds more comfortable driving a broader range of headphones than the DAC Port does, and is therefore the more capable and versatile amp.
•DAC sections compared: both DAC sections are good, but on the whole the DAC Port would get the nod, in part because its sound is so refined and well-defined, with nary a trace of the somewhat dry-sounding highs that the iQube sometimes exhibits. Add to this the fact that the DAC Port can handle high res files, which the iQube V2 cannot, and it becomes apparent that the CEntrance DAC section is the more capable performer overall.


Qables’ iQube V1 and V2 share a terrific-sounding amplifier design that offers a very desirable sonic combination of openness, delicacy and detail, on the one hand, coupled with a rich, hearty and full-bodied quality on the other. While the amp can exhibit a touch of treble dryness at times (or at least does so when used with some headphones), this is a small price to pay for the many other things the amp does well.

The DAC section of the iQube V2 offers voicing and overall performance similar to, but definitely not identical to, that of the iQube amplifier section. Specifically, occasional hints of treble dryness are audibly more pronounced through the DAC than through the amp—an issue that may bother some listeners, but that will seem small if not inconsequential to others. Finally, the DAC can handle digital audio data files with resolution up to 16-bit/48 kHz (but not higher) meaning that for obvious reasons this not the right DAC for those looking to download and explore high res digital audio files.

On the whole, then, I see the iQube V1 is a very compelling (and exceedingly well-built) headphone amp that should enjoy broad appeal. Though the V1 is certainly not cheap, its very high build quality certainly helps justify its price.

The iQube V2 can also be an appealing product, especially if your preferred headphones tend not to expose the minor though potentially audible sonic drawbacks of the V2’s DAC section. Given the iQube V2’s significantly higher price and the good but not great performance characteristics of its DAC, I would say the V2 is much less a “slam dunk” choice than the V1 is.


Qables iQube V2 Portable Headphone Amplifier/DAC
Frequency Response: 5Hz -50 kHz, - 1dB
THD+Noise: 0.03% maximum, 0.01% typical
Analog Inputs: 3.5mm mini-jack
Digital Input: mini USB jack
USB DAC: 16-bit, 32/44.1/48 kHz resolution
Analog Outputs: 3.5mm mini-jack
Input Impedance: 10 kOhm
Headphone Output Impedance: <0.5 Ohm @ f<5 kHz, <1.5 Ohm @ 20 kHz
Headphone power output: 20Hz – 20 kHz
• 160mW @ 16 Ohm
• 80mW @ 32 Ohm
• 12mW @ 200 Ohm
Power Supply: mini USB jack, 5V ± 5%, 0.4A power consumption
Dimensions (H x W x D): 6” x 1” x 4.5 d x 1”
Weight (with batteries): 200 grams
Price: $699

Qables iQube V1 Portable Headphone Amplifier
Frequency Response: 5Hz -50 kHz, - 1dB
THD+Noise: 0.03% maximum, 0.01% typical
Analog Inputs: 3.5mm mini-jack
Analog Outputs: 3.5mm mini-jack
Input Impedance: 10 kOhm
Headphone Output Impedance: <0.5 Ohm @ f<5 kHz, <1.5 Ohm @ 20 kHz
Headphone power output: 20Hz – 20 kHz,
• 160mW @ 16 Ohm
• 80mW @ 32 Ohm
• 12mW @ 200 Ohm
Power Supply: mini USB jack, 5V ± 5%, 0.4A power consumption
Dimensions (H x W x D): 6” x 1” x 4.5 d x 1”
Weight (with batteries): 200 grams
Price: $549


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