Linear Tube Audio MicroZOTL MZ 2.0: A second opinion

By mrgoodsound

Editor: This is indeed a Milestone for this Blog! Readers should examine the two distinct views and think philosophically! Perhaps Leave a Comment? Have Fun!

Today's article will be very unique, in some ways a first for the blog, and my most ambitious yet since doctorjohn invited me to start writing a column some months ago.

For context, over two months ago I exited my loudspeaker purgatory by acquiring a pair of 1978 La Scala's. I absolutely love these speakers and mean to provide something of a write-up on them, but several adjustments to my listening room need to be completed first. In the interim, I was searching for a low power (<10 watt) amplifier I could replace my Lance Cochrane 6550 amplifier (50 watts) with to fully exploit the La Scala's efficiency. I was very intrigued by doctorjohn's praise of the microZOTL2 and after some deliberation placed an order for my own unit, with the intention of using it as an integrated amplifier.

I will spoil the conclusion of the article now: the sound did not work for me and I made arrangements to return my unit to the manufacturer. What follows below is hopefully a coherent analysis of why that is and how I reached my conclusion. Please note I do not really consider it a 'review', nor do I consider myself an 'audio reviewer'. The term makes me cringe, as it has been bastardized by the mainstream audio press and their casual relationships with industry manufacturers. However, it will be a unique opportunity to provide a second opinion to my colleague doctorjohn's on the microZOTL, something which we rarely (read: never) see from the 'professional' audio reviewers. And why not? Multiple perspectives are necessary to reach critical consensus, and infinitely more useful than just one. Sadly, you will not see this from the advertiser-relationship driven audio press. It would not make much sense having two writers tell you how great one component from one manufacturer is when they could each be busy telling you how great two different components from two different manufacturers are.

In recent memory, I can think of only one mainstream review which offered a second follow-up opinion, and that was the BorderPatrol DAC in Stereophile. Unfortunately, it was offered for entirely the wrong reasons: disingenuous journalism to push a predefined agenda, at great cost to the integrity of Stereophile's staff. The original review and follow-up are linked above, though you can read more about the context of the situation in this article from Part-Time Audiophile.

My System

I have never really described my playback chain in detail for the reader, as it has been in a state of constant flux for the last 6 months. I will lay it out now for the context. I currently only use a digital source as my 6 (six!) turntables are all in various states of disarray. This front-end consists of a HP laptop running Windows 10, feeding USB to a USB/SPDIF converter, which feeds S/PDIF to my abbasaudio DAC. The DAC is TDA1541 based and has a low-impedance triode output stage capable of a healthy 4.0V RMS. It can drive an integrated amp directly. My pre-amplifier is The Truth which provides volume control and source switching for the Lance Cochrane 6550 amp. I would like to state I am not really dissatisfied with any aspect of the Cochrane amp's performance. In fact, I am surprised time and time again at just how good it is. However, I did want to see what was possible with lower power, fewer active stages, etc. to really bring out everything my source has to offer. Call it the audiophile's curse. The La Scala's are placed in the corner of the room, angled in 45 degrees to the center, in accordance with Paul Klipsch's placement instructions. Once I tried this placement I stopped considering in-room placement, despite having a good amount of space. Belden 9497 speaker wire is used, my interconnects are all random, nothing fancy, only copper or tinned copper wire.

Options Power supply I ordered the Switch Mode PSU. This is because I really wanted to see if the unit worked in my system before investing in upgrades (in hindsight, a very wise choice) and doctorjohn's praise was sans LPS. Besides, I could always upgrade later. Tubes I requested the NOS upgrade tubes. While I agree with doctorjohn that current production tubes have gotten better, I still avoid them any which way. They always sound coarse and lacking in refinement to old production. I also avoid tube rolling, I prefer when the manufacturer can just supply me with 'the good stuff', like they did in the old days! Remote Yes for me. Remote control for volume adjustment is so important for me. I do not want to be enraptured in a performance and glued to my seat only to feel the volume is one tick too quiet or too loud. I do not want to get up between recordings of varying gain levels. Most importantly, I tend to stand up and pace around the room when listening. This is a weird trait of mine, I don't really know anyone else who does this, but I like to have the remote in hand and be able to adjust the levels as I walk around.

Day One

Impressions of build quality, finish, pride of ownership are all very high. It feels like a premium unit and I love the see-through top cover. I had already waited three weeks for the unit to ship, so when it arrived I immediately finished work and set it up, connecting my DAC to its RCA input. I did not listen to my system as it was (generally, this is an evaluation mistake) and fired up the MZ2. There was no background even with my ear against the tweeter, which cannot be said for every other amp I have tried with the La Scala so far. The manufacturer had advised no burn-in required, so I began listening right away with a live recording of Glenn Gould live in Moscow Conservatory (1957), streamed from YouTube. (I think another article detailing my obsession with Gould is soon due).

I was taken with what I heard right away! The benefits of removing active stages and output transformer were evident in increased immediacy and physicality. The notes were sharper, each individually more distinct, lending to an impression of increased intelligibility and drive. I recall cheering internally, that the microZOTL was a success and that this was the best piano playback I had yet heard. I listened enraptured to the rest of the recording, which unfortunately is incomplete and ends abruptly in the middle of Fugue #4. Desiring more Gould, I put on Haydn Sonata no. 3 from Columbia ML 5274 (the YouTube link I provided is unfortunately 'remastered' and neutered compared to the local file I have). This was just as exhilarating as the live Moscow recording and I felt rather confident after just two recordings that the microZOTL was the bee's knees.

Unfortunately this confidence would be short lived. I began to explore pop/rock favorites and grew rather concerned about what I was hearing. First was Joan Baez's cover of Fountain Of Sorrow. This is a very typical mid-70s pop production from A&M on early transistors. Very clear and distinct vocals with some light overdubbing and snappy accompaniment. What stuck out with the microZOTL was not pleasing, the snappy accompaniment became annoying and sharp; Joan's voice was thinner than expected and a bit detached, despite piercing clarity and forwardness. Technically, the sound was impressive, all the stereo pop record tricks were highlighted like fireworks, the bass was 'tight', but the sound had an unnatural insistence to it not unlike servo-controlled direct drive turntables. I was disappointed and put on a few other pop records, wondering if it was a fluke, but unfortunately heard more of the same. I decided the unit needed break-in and left it to run signal overnight.

Day Two

I returned after the unit had 24 hours of play time and ran through the same recordings as yesterday as well as new ones. I cannot say the sound character changed at all, and I heard the same traits. The playback was too damped; similar to what I would expect listening to the raw multi-tracks of a pop record in a studio on an analytical monitoring system. There was a lack of weight or gravitas around the middle frequencies, voices in general seemed shifted a pitch up. I played all sorts of 60s pop/rock such as Hendrix, The Mamas & The Papas, Jefferson Airplane, etc. hoping to hear a baggier or fuller sound, but it did not come. I did not have a strong desire to listen and decided to return after the 100 hour mark had passed.

Day Five

I returned after the unit had 100 hours of play time and ran a loop again through all the same recordings, listening acutely for improvement in my areas of concern. One thing is for sure, the sound character did not change at all with break-in! I had watched the Johnny Cash biopic Walk The Line (2005) the previous night and decided to run through some of his catalog with the microZOTL. This was the final straw, Cash's voice was lacking its smokey Southern chestiness and I found the rockabilly tunes repetitive and fatiguing, despite impeccable 'timing'. This was especially shocking considering I had just been enjoying them on my Vanatoo desktop speakers the night before.

At this point, I shut off the microZOTL and switched back to the Truth + Cochrane combo. After 15 minutes of warm-up I played the same Johnny Cash tunes. Instant relief! The body returned to his voice, the accompaniment was certainly a little more smeared and not as lithe but certainly played with more warmth and communication of musical intent. If anything, the little bit of smearing contributed to a greater sense of 'human' playback. An analogy can be drawn to the 'quantization' of modern pop/rock records which removes all human elements in favor of perfect transients and timing. The effect here is not so drastic but easily felt when switching back and forth.

I went in a complete backwards cycle, playing through every record from the past week and with each felt more relief, less annoyance, more enjoyment and relaxation. I came full circle to the same 1957 Gould recording from day one and realized that I preferred that too on the Truth + Cochrane. The recording was actually transformed, as if I was hearing an entirely different interpretation of the same piece. Gould's playing was less frantic, the individual notes stood out less but their relationships and melodies a hundred times easier to absorb. Intonation especially in the low-end came through clearer. Despite having four cascades (6SN7 input, 12AU7 voltage gain, 6CG7 phase inverter, 6550 output) and an overkill power rating for my speakers, the Lance Cochrane amp scored higher where it mattered.

At this point, my thoughts on the MZ2 must read as very critical and fairly negative. I want to be fair to it as a component and provide a description of its sound, in my system, absent from the feelings experienced or recordings played in the past week. To do so I will use the framework for all aspects of sound provided by Anatoly Likhnitsky's 7 Words About Audio Examination Errors (2001) to dissect the MZ2's sound character.

• Sound proportions (include tonal balance, spatial impression, clarity of sound and dynamics).

Tonal balance is linear, although slightly devoid of euphony or saturation. Spatial impression is distinct with regards to stereo effects as aural objects are thinner, sharper, less stuck together. Clarity of sound as it relates to absence of veil and electronic masking is very high. Dynamics are sharp but the sound is lacking in satisfactory fullness in the LF which in turn affects the dynamics.

• Soundness of sound (includes vividness, saturation, brightness and naturalness of sounding of music tones).

Saturation is lacking. Voices, wood instruments have a slight pallor, lack of rosiness. Many musical tones take on a frantic, insistent characteristic that can be distracting. Brightness and vividness are present in that the sound is forward and un-obscured, but is more like monitoring a direct mic feed than playback of a finished record.

• The emotional content of the “sound” (energy, emotional mobility, emotional diversity of the sound of music).

At first confusing and paradoxical, why the emotional content of sound is absent despite the presence of technical excellence as it relates to timing, rhythm and articulation. Ultimately, the sound is stripped of emotional content for the above reasons. 

• The spiritual content of the “sound” (a sense of the appropriateness of the distribution of musical sounds, the nature of their sound production, intonation, dynamics, rhythm, etc.).

The highest level of perception, which is inaccessible due to the shortcomings listed above. The greater sense of intelligibility from the microZOTL is false, as it is technical and not spiritual or emotional in nature. I really wish this wasn't the case, as for me it is the ultimate damnation of any audio component.

Conclusion

So, you can tell by now the microZOTL is not for me. The technical reasons behind this I can only hypothesize about. You will probably notice that I have not referenced anything from doctorjohn's initial post about the MZ2. This is because I don't actually disagree with anything he said, though obviously our conclusions on it diverge. I could have read his post 100 times and still not have been prepared for what my experience was, but this does not make his review a bad one. Just the same, you may read my impressions and be largely discouraged from trying this amplifier, but you might really like it! When I get curious about something, I try it for myself and form my own conclusion, that's that. Victory or Defeat? I know a lot of people get discouraged when they get a new component and it is not 'the one', and treat the experience as a defeat to recover from. I do not regret at all trying the microZOTL. I have eliminated a curiosity, gained experience, and perspective on where to go next.

Output Impedance The ZOTL amps all have very low output impedance specifications. For the MZ2 it is 2ohms. I have a hunch this is largely to blame for the 'over-damped' character, stripping the sound of its emotional mobility and diversity. I know that when it comes to headphone amplifiers, there is a trend towards a very low OI (<1 ohm) being the most desirable and 'accurate'. This is horseshit, and in my experience these amps sound the worst of them all. Perhaps this issue is only exacerbated by the 16 ohm La Scala's. The Circuit In Sound Practices issue #15, editor Joe Roberts slips in this paraphrased quote: "Sure the Loftin-White was a great amp but if it was that great why isn't everyone listening to Loftin-Whites?". I believe the same can be said of the ZOTL circuit. The transformer is being replaced in the circuit by an impedance matching network of surface-mounted resistors, which will bring its own sound compromises like everything else. For me this was not preferable to transformer coupling. The Evil Output Transformer Actually, the entire basis of ZOTL is that output transformers are a source of distortion which should be eliminated. I will not try to argue with what the scopes say. I will say that there are schools of thought which view the output transformer as a necessary randomizer of sound. The curious and intellectual reader may learn more from Anatoly Likhnitsky's Formula of Sound. With Pre-amp Something that I am not able to try, which doctorjohn did, is use the MZ2 with an active line stage before it that would have a complimentary sound character. I only have The Truth, which does not have much character to speak of, and didn't help the situation when placed before the MZ2. I will say that I never felt the MZ2 was running out of steam or drive with the La Scala's, output power and gain were definitely not concerns.

doctorjohn also asked me to assess the MZ2 as a pre-amp and headphone amplifier. The two components I have for these categories, The Truth line stage and the abbasaudio OTL headamp, I already consider to be 'best in class', and the odds are stacked highly against the little ZOTL amp. I did try it as a pre-amp in front of my Lance Cochrane 6550 and as a headphone amplifier driving my modified HD600s. My conclusions are in-line with what I wrote about it as an integrated amplifier, although its primary shortcomings (lack of euphony, damped sound character) were more apparent listening with headphones as I am particularly sensitive to these aspects there. I will note that the MZ2 performs all three functions and costs the about same as just one of the dedicated units it battled against.

Lastly, a bit of an easter egg in the film Walk The Line (2005). In one scene Johnny Cash (Joaquin Phoenix) is in a radio station ready to debut his first single, when the operator asks him to flip the record. Given that this scene was supposed to take place in the mid-50s, the broadcast equipment is very accurate! You can see a Gray Research 106SP tonearm in action, mounted to what must be a Gates or Rek-O-Kut 16" transcription table. Good attention to detail from the Hollywood set designers!