Marley MkII headphones amplifier

Named after the reggae legend, the Marley MkII headphone amplifier is a paid-up member of the latest Rockstar series from M2Tech and designed by innovative Italian duo Marco Manunta and Fabio Elia. Rockstar compartmentalises the functions of a hi-fi system into a number of smaller boxes to provide a higher level of performance and more generous feature set, and allows listeners to grow their systems at their own pace by buying only the components they need when they need them. With matching aesthetics and dimensions, each half-width unit measures just 5cm high and can be stacked to alleviate the recurring need to conjure rack space.

When Jason Kennedy visited M2Tech in Pisa last September the six-strong supergroup was neatly organised in a two-by-three formation atop a standard-width Pioneer DVD Player, occupying a total space just 40cm wide in the demo room. Wrapped in aluminium, these latest boxes have a strikingly minimalist, architectural form that’s the antithesis of the intricate, CNC designs found elsewhere. The thick, curved metal plates serve as heatsinks and RF shields, inspiring clean lines that are easy on the eye and contrast nicely against the black plexiglass front panels.

Marley’s front panel houses two headphone outputs (one 6.35mm single-ended and one 4XLR balanced), a high-contrast OLED display, an ‘encoder’ dial that adjusts volume and other settings, and a power/mute button. Protruding just a little more than the overhang of the casing, the dial is on the shallow side and may present a challenge for fatter fingers. This headphone amp’s many features are, however, all accessible using the supplied remote which can control the entire Rockstar line. There is also an iMarley app for Android and iOS that I highly recommend as it makes controlling the amp a breeze.

The rear of the unit is bursting with connectivity. There are three sets of inputs (two single-ended RCA and one balanced XLR) and two sets of outputs (both single-ended RCA – one fixed-level record output and one variable-level preamp output). XLR outputs are absent, this would necessitate a taller enclosure spoiling Marley’s uniformity with the other Rockstar boxes. The small ‘widget’ adjacent to the XLR inputs is the Bluetooth antenna that allows the iMarley app to communicate with the amp. In addition to the DC input for the bundled 15V power supply there is a 4-pin socket reserved for M2Tech’s optional low-noise Van Der Graaf MkII power supply. 3.5mm trigger inputs and outputs allow Marley to power on or be powered on by a connected device.

10 watts per channel
Manunta’s “literally all you need for a first-class headphones listening experience” claim is tough to dispute, this little box boasts a suite of specs and features that arguably satisfies more needs and desires than any other earspeaker amp I’ve reviewed. It employs a discrete design with FET input and balanced Class-A power amp circuit that runs surprisingly cool to the touch. An ultra low-noise dual regulator is said to be responsible for its silent background with even the most sensitive of ‘phones, the single-ended and balanced outputs deliver impressive signal-to-noise ratios of 115dB and 118dB, respectively. I don’t use IEMs so cannot plumb the full depths of Marley’s noise floor, but when I plug my most sensitive over-ear model into the 6.35mm output I hear zero hiss from this unit.

The generous 10Vrms delivered by the single-ended headphone output is on a par with the superb Sparkos Labs Aries I reviewed last year that consumes substantially more desk space. What’s more impressive, however, is its claimed ability to sustain 9Vrms into an 8 Ohm load, that’s 10 watts per channel, with only 0.0008% THD. Maximum output from the balanced 4XLR socket doubles to a brain-melting 20Vrms (18Vrms into 8 Ohms), placing it amongst the most powerful headphone amps on the market. The fixed gain means these voltages are achieved with a 1.1Vrms input when Marley’s volume is set to max.

An email exchange with the designer reveals that Marley’s circuitry is not actually balanced from input to output as you might expect. The power amp is balanced but is driven in single-ended mode. Manunta explains, “one side is driven with the input signal while the other is grounded, the coupling between the two sides is done by the feedback network”. The XLR input is converted to single-ended but, unlike typical summing circuits, M2Tech’s “unbalancing circuit” preserves the level of the input signal instead of cutting it by half and therefore improves the signal-to-noise ratio. I can’t claim that I fully understood the pros and cons of this approach but the proof is in the listening and, in my system, the M2Tech’s XLR input wins out despite the additional conversion. The sonic differences between the two input stages are, however, subtler than those in other headphone amps I’ve reviewed and I expect the preference for one over the other will depend on the source.

The extent of Manunta’s attention to detail is evident throughout this amp’s operation. The analogue volume is controlled in the digital domain; it spans 85dB, can be adjusted in either 0.5dB or 1dB increments, maintains perfect channel matching across its entire operating range and can be set to default to zero or to the last used setting at power-on. A -20dB muting button evokes memories of indulgent hi-fi from the past, a now much overlooked provision that’s handy for quickly lowering the volume without interrupting playback. The +/-6dB balance compensator allows listeners to dial-out in 0.5dB steps their less than perfectly matched hearing sensitivities, extremely useful if you perceive the centre image pulling slightly to one side when listening through cans. There’s even the option to activate a momentary level fade-out and fade-in to avoid the potentially abrupt changes in level when switching between inputs.

Crossfeed in one
The pampering doesn’t stop there. A crossfeed circuit can be engaged to make the headphone experience more akin to loudspeakers by mixing a time-delayed signal from the left channel into the right and vice versa. The designer points out that this is particularly useful with older recordings in which instruments suffer from extreme left-right placement and helps reduce listening fatigue. Marley’s crossfeed is a simple on/off affair so there is no opportunity to fine tune. This isn’t a bad thing in my book, when I auditioned the SPL Phonitor 2 I caught myself incessantly tweaking its three-pronged crossfeed matrix instead of enjoying my music. Chord Electronics has arguably achieved the best compromise with its ‘mild’, ‘medium’ and ‘strong’ presets, but I did find Simaudio’s Moon 430HA implementation to be well-judged which proves that a single, fixed setting can be effective if the designer gets it right. Marley’s crossfeed is one of the bolder implementations I’ve heard and its effect is easily noticed. It works wonders and is a must, in my view, when listening to the stereo Beatles catalogue as it gets rid of that rather crude left-centre-right split that sounds especially disjointed over headphones. Contemporary studio and venue recordings escape this problem by and large and there’s usually little benefit in applying crossfeed to these, I often find it does more harm than good by needlessly narrowing the stereo image and removing musical information in the process.

Another interesting aspect to this amp is the ability to change headphone output impedance (aka ‘Z’), the idea being that low- and high-impedance ‘phones are designed to be and/or sound better driven with low- and high-Z’s, respectively. While there’s certainly some truth in this, it isn’t only the nominal impedance but also the shape of the headphone’s impedance curve that affects this. The latter determines which frequencies will be attenuated by the amplifier’s Z while the former indicates how pronounced the effect will be. Z also affects damping and transient response, that is how quickly the earspeaker responds to dynamics in the music. It can therefore also be used as a means of tuning the perceived speed of the presentation, higher Z’s tend to encourage more bloom with longer decay times.

Rules of thumb are useful but the best way to discover the optimal Z is through listening and the M2Tech gives us three choices to explore, Low-Z, 10 Ohm and 47 Ohm. My preferred setting depended not only on the headphone but also the genre of music. With electronica, jazz and rock I mostly favoured Low-Z for the fastest dynamics, but for classical and easy listening I gravitated to the higher settings for a more relaxed experience. 10 Ohm was an especially good match for the Focal Utopia (80 Ohm), it moved me a row further back from the stage and offered a slightly warmer presentation without sacrificing this earspeaker’s breathtaking clarity. A similar result was achieved with the Sennheiser HD600 (300 Ohm) on 47 Ohm. The effect of increasing Z on this amp is less exaggerated than on the Audio-Technica AT-HA5050H tube-hybrid I reviewed in 2019 and, if nothing else, demonstrates that numerical comparisons between amplifiers are of limited value. On more than one occasion I enjoyed Utopia with Marley set to 47 Ohm which, according to Ohm’s Law, yields a woefully low damping factor that should not work, yet it sounded sumptuous. That’s the beauty of this amp, the listener gets to decide what works and what doesn’t.

Marley’s most controversial feature, perhaps, is the refreshing inclusion of tone controls, embracing the reality that staying true to the original signal isn’t always the route to audio nirvana when faced with imperfect recordings, headphones, hearing, or the unashamed desire for a more colourful sound. The three-band EQ permits up to +/-12dB adjustment of bass, mid and treble in 1dB steps, the fixed centre frequencies and slopes provide broad and gentle contouring (listeners requiring more targeted frequency correction will, I expect, continue to use DSP-equipped sources). It’s worth noting that, like the crossfeed circuit, the tone controls aren’t in the signal path unless activated, which should put purists’ minds at ease. Marley’s EQ encouraged me to explore areas of my library I’d previously designated no-go zones with certain headphones and, after a while, my entrenched audiophile habit of letting the ‘phones pick the music began to wane.

Sound quality
R.E.M.’s Automatic For The People (1992) is surprisingly high-fidelity for an alternative rock album, it’s mastered on the bright side but there’s plenty of separation in the mix and a transparent system should present it with a vibrancy and openness that’s refreshing but not fatiguing. Marley resolves the layering of the mandolin, guitars and piano, the attack and decay of the percussion, especially the claves, and the placement of the lead vocals and background ‘oohs’ in Man On The Moon with pinpoint precision. Transparency is as good as I’ve heard from a solid-state offering in this price bracket, it’s not only faithful to the recording but also to the partnering headphone and on Low-Z delivers transients at a velocity that easily matches my fastest open-back.

Each ‘phone puts its own spin on this alt. rock classic, but they all do justice to its enigmatic soundscape and show that Marley has a neutral tuning that favours neither warm- nor cool-tilted cans. Separation is impressive and tone is impeccable on the Sennheiser HD600, each instrument has the perfect blend of body and bite. The more forgiving HD650, by comparison, offers a slower and lusher presentation with a warmer bottom and softer top that smooths over some of the finer textural details and spatial cues, but the track’s energy is still articulated extremely well. Audio-Technica’s ATH-ADX5000 delivers the widest and deepest soundstage with the crispest transients and airiest overtones and picks out every instrument in the mix with a surgical exactness. On the end of a lesser amp this 420 Ohm flagship open-back from A-T can be fatiguing in the upper registers, which is perhaps why many partner it with tubes but, like Sparkos Labs’ Aries, Marley shows that the ADX can be trusted with solid-state if it’s up to snuff. Increasing Z to 47 Ohms does, however, take the enjoyment factor with this headphone up a notch by enriching instruments’ lower fundamentals and tempering its breakneck speed so that those ultra-clean notes can be savoured for a smidgen longer.

Whenever I’ve reviewed headphone amps that offer both single-ended and balanced outputs I’ve invariably preferred the latter, often by a wide margin. Greater headroom and eliminating the common ground plane, in my experience, almost always delivers a more thrilling and immersive listen with stronger grip, harder hitting dynamics and more space around instruments. Comparing Marley’s quarter inch jack and 4XLR outputs leaves my preference for the latter intact but in this instance I’m pleasantly surprised by how subtle the differences are, a lot of effort has evidently gone into minimising the performance gap between the two. The Bee Gees’ Size Isn’t Everything (1993) is abundant in synth-generated low frequency information and it’s with tracks such as Heart Like Mine you notice the 4XLR output’s superior bottom end solidity and extension. The difference isn’t huge but if low frequencies are a priority it’s definitely worth driving your headphones from Marley’s balanced output if circumstances allow.

At the end of my audition I couldn’t resist entering the M2Tech into a mini bake-off against the Sparkos. Aries made such an impression on me when I reviewed it last year I actually bought one and it has since become my reference headphone amplifier. I was amazed by how similar these two amps sound, not only in tone and texture but also timing and imaging. Both are transparent to the extent that you’re effectively listening to the strengths and limitations of your source. If I swap out my reference DAC (the Schiit Audio Yggdrasil) for the Chord Hugo 2, for example. the resulting change in presentation is far more audible than the differences between the headphone amps. If I was pushed I’d say the Aries edges it on musicality, but I wouldn’t want to put money on this in a blind A/B test.

Verdict
M2Tech’s Marley MkII is probably the most bonafide one-stop-shop for headphone listening I’ve ever used. Apart from XLR preamp outputs, I cannot think of anything else that would make this transparent, powerful, highly feature-packed headphone amplifier more appealing than it already is at this price point. No matter where you are on your headphone journey, Marley delivers a level of performance and adaptability that won’t be easily outgrown. I dare say this little Rockstar has the attributes to become a legend like its namesake.