Linear Tube Audio MicroZOTL2.0 Tube Headphone Amp Review

The MicroZOTL2.0 headphone amplifier and preamp is one of Mark Schneider’s latest reconfigurations in the world of audio sources. Featuring quality components, the amp also incorporates the ZOTL (Zero hysteresis Output Transformer-Less) technology which has earned numerous awards and been heralded a success in recent decades. The first implementation of this was, of course, in David Berning’s original MicroZOTL whose architecture came into fruition in the late ‘90s.

Schneider’s modern take, however, aims to deliver sonics that match and even surpass its predecessor with the vision of delivering “stunning sound quality” in the home setting. Having had an extensive background in engineering, manufacturing and product design, Mark was attracted to the opportunity of working with Berning’s complex and desirable creations. It was with this passion that 2015 saw the founding of Linear Tube Audio, an audio company which strives to continue and build upon the successes of the original ZOTL technology. As if this were not enough, Mr. Berning personally oversees the initial run of the microZOTL2.0s to ensure the amps meet his strict criteria.

The $1,100 amp operates under a push-pull design with stock 6SN7 Russian tubes that can put out 1 Watt per channel as a stand-alone amplifier. As with the original, the microZOTL2.0 uses a “highly refined” no-feedback Class A triode design which in addition to the power supply and impedance conversion circuit make this amp a low-current one. The obvious advantage to this is that less stress is applied onto the tubes extending their life expectancy. An upgradeable power supply, touted the Linear Tube Audio ‘Linear Power Supply’ can also be bought for an extra $595.

Box and design

The MicroZOTL2.0 comes well-packaged in a large sized cardboard box with thick heavy foam inserts. Though more utilitarian than thrill-ridden, the packaging served its purpose of arriving in one piece across the trans-Atlantic.

The MicroZOTL2.0 offers a strikingly unique design which makes use of a clear glass acrylic top where the circuit components can be seen without dismantling. Some may consider the internals to be visually unappealing but I for one am happy with the insight into the tube amp’s workmanship. The front plate is made from aluminum and comes in a choice of black or midnight blue.

Build & Features

Front

The MicroZOTL2.0 has a very clean front interface compared to that of the Violectric V281s. Although this has the benefit of a more aesthetically pleasing and minimalist design there is the obvious drawback of less utility options for the end-consumer. Nevertheless, the lack of a balanced input can be overlooked on the basis of appearance and convenience. On the far left hand side of the amp, there is a power button with a bright red LED display. Next to this is an input switch which toggles between two separate inputs. At the center, there is an ALPS potentiometer which feels smooth to the touch with good tactile resistance; it could however, have benefited from dialed markings and more clearly defined volume markers like those used in the V281 amp. On the far right of the device is a 6.35mm jack which can be secured with the red locking plastic mechanism. To release, the red tab needs to be pushed while simultaneously pulling out the cable.

Rear

On the rear of the ZOTL2.0, there are a plethora of inputs and selections. For example, the far left side hosts speaker and preamp outputs while the far right hosts the two RCA inputs. The power port, which is located on the bottom right of the device, can be connected to the 12V power supply attached.

Internals

The MicroZOTL2.0 adopts much of the same internal circuity as that of its predecessor. However, what has improved is that the power supply has been externalized, the volume pot has been made with higher grade material, preamp outputs have been included and there is now the option to select between two inputs. The stock tubes have also been rethought and now include the Russian Tung-Sol 6SN7 variant.  

Sound impressions (w/ Linear Power Supply & Stock Tubes)

The MicroZOTL2.0 offers a unique tonality which is unlike many of the amps that I currently have to test it against. It brings to the table a liquid and immersive sound that does well in making music  engaging and lively. Often, neutral amps do very little to appease a musical and forthright sonic image and so when one does so, it is certainly refreshing to hear.

Starting from the bass, there is good amount of impact and slam. While not the tightest of low frequencies I’ve ever heard, there is generally a good sense of speed and articulacy. The Schiit Ragnarok, in comparison, presents more bottom-end heft and tightness but the MicroZOTL2.0 does good to convey some of the former’s speed and articulation. Paired with the Schiit Yggdrasil, the MicroZOTL2.0 is adept at the portrayal of micro-details and nuances at the lower end of the frequency range. The Violectric V281, on the other hand, has a faster bass decay than the MicroZOTL2.0 with its more analytical ‘solid-state’ signature. Overall, though, the bass of the MicroZOTL2.0 is respectable; it is able to dig deep and offer a pleasurable tonality that captures the essence of the solid-state’s speed whilst maintaining the charm and liquidity of tubes.

This tonality carries on through to the midrange where vocals carry a good sense of clarity coupled with some sweetness. Where the MicroZOTL2.0 differs in its timbre with other tube-based set-ups though, is that less emphasis is placed on an otherwise euphonic midrange. Instead, the mids sound ever so slightly recessed with a soothingly agile character which captures the best of the tube and solid-state world. A good comparison sees that ALO Audio’s Continental Dual Mono tube-hybrid amp sounds warmer in the midsection next to the perceptively clearer midrange of the MicroZOTL amp. Both amps however possess a good level of engagement albeit in different ways of achieving the same goal. With regards to imaging, the MicroZOTL2.0 has a relatively large soundstage eclipsing that of the Schiit Ragnarok and Mjolnir 2 amp.

In Andy James’ “The wind that shakes the heart”, the high frequencies are beautifully presented with this addictively sweet and extensive character which the MicroZOTL2.0 seemingly excels at. Despite not being the most realistic presentation of treble notes, the signature is nothing short of being clear and rich at the same time. Yes, the Ragnarok is more transparent and shows up higher levels of detail across the auditory spectrum but the MicroZOTL2.0 really does well to evoke an engaging and yet non-fatiguing sonic experience.

Part of the reason that the MicroZOTL2.0 is able to offer a different flavor of the tube-based sound is that it uses no output transformers. This allows micro-details to shine through without the unnecessary distortions and artifacts which plague other tube-implemented devices. The MicroZOTL2.0 is also unusual in that it generates very little heat and owing to the low-stress design enjoys a 10,000 hour tube life. It must also be noted that with tube rolling, the sound characteristics of the MicroZOTL2.0 are susceptible to change with various accounts claiming for the better. Having not tested any of the NOS tubes myself, though, it is difficult to recommend any.

Matching

The headphones used in this portion of the listening evaluation were HiFiMAN’s HE-400S, Edition X, Sennheiser’s HD800/S and the Fostex TH500RP. All of which were easily able to be driven with plenty of headroom to spare. The MicroZOTL2.0 was also able to handle IEMs such as Ultimate Ear’s Reference Monitors and Rock-it Sounds R-50s. Although the MicroZOTL2.0 can drive efficient speakers to moderate volumes, I did not test them in this aspect. According to Linear Tube Audio’s website they can be driven to volume levels starting from 89dB (for non-critical listening) and 97+ dB for critical levels of listening. An admirable trait that the MicroZOTL2.0 showcases is that no audible background noise can be heard even with the highest volume settings implemented.

Conclusion

Overall, the MicroZOTL2.0 is a great tube amplifier which capitalizes on certain traits not often associated with tube set-ups including its slightly lean and agile midrange as well as its extensive treble. The build quality is magnificent and together with its peer-in display makes for a really classy looking device. It must be noted that the linear power supply is a highly recommended accessory for this type of system to truly get the best out of the MicroZOTL2.0. While $1,699 is a considerable amount of money, I have achieved some outstanding synergy with top-end transducers. Yes, there could be a balanced out option and the additional power supply is not the cheapest but the MicroZOTL2.0 does well in reigning home a relaxed and yet involving sonic experience. Together with the ability to tube-roll and its pleasurable character, this amp is deserving of at least an audition. Stay tuned for more.

Unless otherwise indicated, this is a preview article for the featured product. A formal review may or may not follow in the future.