MicroZOTL 2.0 Review

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by purr1n, Mar 30, 2016.

  1. purr1n

    purr1n Desire for betterer is endless.

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    MicroZOTL 2.0 Review

    Measurements Here: http://www.superbestaudiofriends.org/index.php?threads/microzotl-2-0-measurements.1724/

    When it comes to audio gear, I’ve been known to be a black or white kind of guy. Thumbs up or thumbs down. The MicroZOTL 2.0 is tough cookie for me to crack. I don’t know if it’s because I’ve reformed and am now gentler kind of reviewer, or if it’s because I have a HUGE amount of respect for a vendor representative to make a showing up here where we tend to pull no punches.

    Those who know me or have followed me throughout the years know that I am extremely demanding of gear and will not hesitate to note even the smallest issues. The primary headphone / speaker amp that I am using now is custom tailored to the sound I want. Please take this into account when reading this review. I would like to think that I am pretty fair though, taking into account cost into consideration when reviewing a product. The MicroZOTL 2.0 costs $1100. Unfortunately this doesn’t make this any easier. $900 to $2100 is a price range that I like to refer to as no-man’s land. This is because the range is more expensive than value products, but within reaching distance of truly amazing high fidelity gear.

    DSC_2227 (Medium).JPG

    I took a few sneak peaks at various reviews and quick impressions from people here on SuperBAF, from Steve Guttenberg, and from Head-Fi. The first thing I wanted to establish was if the MZ2 was warm or bright sounding, since some impressions said bright and others said warm. Well, it’s a little bit of both. Allow me to explain in more qualitative detail: The MZ2 has a glassy, strident treble that I personally found fatiguing over longer listening sessions, particularly with headphones, including the Audeze. I know for a fact that treble sensitive people like Hands, Drfindley, or OJNeg will immediately be turned off by this. The positive side is that the treble sounds clear with clean lines. However, it wasn’t the treble that first struck me as odd, it was the low end. It didn’t matter what piece of music I put on, from the live Eagles Hotel California (XRCD) to Joni’s Mitchell’s Case of You. It was if there was a dark cloud hanging over the bass to the lower midrange. Not dark as in dark tonality (downward sloping frequency response), but more like clouds and haze - a dull monotonic thumpy and thuddy low end which lacked texture.

    In terms of the expectation of a "tube" sound, that is more precisely a correct midrange that tube amps are known for, the MZ2 slightly misses the mark. When people talk about the midrange, it’s really about two things: harmonics and timbre in relation to the midrange, and bass cohesion with the midrange. The glassy timbre and fine lines of the treble were not consistent with the dull thuddy texture-less bass, causing a recessed midrange-like effect. This is in opposition with any well executed tube amps that I have heard where the midrange is the highlight of the show.


    I didn’t have any 12AT7 tubes lying around, but I had many 6SN7s. I intentionally selected some black triangle plate 6SN7s (think 7N7 black triangle plates) for their good sound quality and laid back nature, hoping to smooth out the treble. As it is with all situations where something is changed, I immediately proclaimed to myself “Ah! This is great. This is really really good.” However, reality always hits when one has time to revisit the system and realize that the changes weren’t as huge as you initially believed them to be. Ultimately, the MZ2 was still the same amp. Distortion measurements did show the vintage 6SN7s as having higher order distortion products of slightly lower amplitude.

    Deeper inspection of the MZ2’s more nuanced capabilities revealed a lack of microdynamic gradation, something that well executed tube amps exceed at. For example, in Daft Punk’s Lose Yourself to Dance, Nathan East’s bass guitar work has quality that swings, with tiny rises and falls, little dances in volume, an ebb and flow. The NBM captures this essence reasonable well, whereas the MZ2 sounds stiffer and robotic in comparison, being unable to reproduce the small changes and gradations in volume. Same thing with the aforementioned Eagles track: the intro string work dances like a ballerina on the NBM, but just sort of goes along for the ride on the MZ2. In terms of resolution or retrieval of low level information, which tends to be closely correlated with microdynamics, I found the MZ2 to scale not as well as the NBM, with the differences more striking when moving up to the turntable as a source. The absence of low level information was particularly and immediately noticeable in Joni Mitchell’s voice in the first few seconds of Case of You. Where the MZ2 had the NBM beat was with macrodynamics. The MZ2 had more impact and punch.

    In terms of the MZ2 powering the 93db efficiency Fostex BLHs, to my surprise, the speakers reached decent volume levels with ease. However, the issues with resolution, microdynamics, and bass quality were even more apparent into the speaker loads. The dull characteristic heard with headphones manifested itself across the entire spectrum as a slight haze. Ironically, as a result, the midrange actually sounded more integrated than on headphones. The treble issues were significantly less apparent, but the Fostex drivers are arguably smoother in the treble any of the headphones used here. Soundstage wasn’t impressive with a compressed stage well between the speakers, a lack of depth, and a lack of precise localization. These might not be fair statements given the extreme build and capabilities of my primary amp. But on the other hand, I’ve used these speakers with the Ragnarok, Crest CA2, and even jiggered them to work from a Mjolnir; and from memory, these amps did a better job than the MZ2. I'll leave it at that.

    Despite the little niggles (I'm probably picking on it much harder than most people would), I found the MZ2 able to exhibit a good sense of musicality. The listening experience was pleasant overall. The MZ2 does possess huge elements of the sound of a well-executed tube amp, having that tube richness, but ultimately comes up just short in a few areas. The MZ2 fits nicely in a spot for those who listen to both planar and dynamic headphones on a regular basis who want a bit of that tube sound. (The MZ2 had no problem handling the Audeze LCD2). Currently, there isn’t much choice in terms of amps with a tube that will power both dynamics and planars well. Overall, the MZ2 is nice good-try effort that can be best described as an Asian-Fail. And remember folks, Asian-Fail means you went to Cal Poly or Pepperdine instead of UC Berkeley.

    This is going on the loaner program and we should look forward to other impressions. This and the NBM is going to @zerodeefex. I removed my vintage 6SN7s because I ultimately didn’t think the differences were significant from the stock tubes.


    Usability Notes:

    I did not care for the locking phono jack. The chassis is too light for it. I’d rather pull the phono jack out by accident than drag the entire amp to the ground.

    Too many screws on the top plate makes it a pain in the ass to change tubes. I hate excessive tube rolling, but this is too many screws. When securing the top plate back, make sure you loosely fit all of the screws in part way before tightening them.

    DSC_2229 (Medium).JPG
    DSC_2226 (Medium).JPG


    Others Amps Used

    Laconic Night Blues Mini; Schiit Vali 2 with Telefunken 6DJ8; Custom: two stage SET (5842 driver tubes, x2 parallel 45 tubes cathode biased, amorphous core LL1663AM output and Monolith IT-02am interstage transformers, 50 kHz filament heaters for the 45 tubes, 866a/866/3B28 rectifier based power supply).

    I wanted to use the Laconic NBM because it’s a similar push-pull type of amp except that it is coupled with a real transformer. The NBM is not available outside of Russia. If it were, I'd expect it to be priced between $700 and $1000 depending upon the exchange rate and what how pissed the EU / USA is at with Putin.


    Headphones / Speakers

    Sennheiser HD600 (worn pads)
    Audeze LCD2r2 (Craig’s cherry picked special edition)
    Sony MA900 (with digital EQ)
    Fostex FE168EZ based back loaded horn speaker augmented by a HSU STF series subwoofer


    Sources

    AKM4490 based DAC (undisclosed for now)
    VPI Classic 4, Ortofon 2M Black, Sutherland Ph3D (upgraded with OPA637/627 opamps)
     
    Last edited: Apr 3, 2016
  2. hifi01170

    hifi01170 Acquaintance

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    great review! going to sell mine as the sound signature is not my cup of tea!

    AKM4490 based DAC (undisclosed for now).................. Is a Schiit DAC??
     
  3. chakku

    chakku Friend

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    Preproduction Modi 4490 ;)
     
  4. bazelio

    bazelio Friend

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    Really nice write up, Marv. I have some thoughts, and am curious where you agree/disagree...
    • Someone somewhere (and I forget who and where) said to me that with this amp tube rolling before replacing the stock power supply would be like getting a frontend alignment on your car but not properly mounting and balancing your tires. This is a bit dramatic. But, if I'm being honest, an album like Sara Bareilles Brave Enough Live had me tearing off the headphones and begging for mercy after a few songs at first and now is quite enjoyable with the Sigma-11.
    • Tube rolling. They're both junk tubes, and only swapping the 6SN7s doesn't go far enough. But with that said, I do feel the MZ2 really works hard to resist change to its sonic signature from tubes, like it's got a mind of its own. I haven't found romance yet... not sure if I will.
    • Distortion plots. I would think any $200 SS amp is going to show a cleaner plot than tube amps priced many times higher. THD itself may not be as instructive as its characteristics, which might deserve being touched upon.
    • My main dislikes out of the box were the treble first and foremost and the lack of low end detail. You've noted both. Interestingly Dick Olsher noted the electronic sounding treble, although not when listening through headphones. Strange, because that's precisely what I heard through headphones particularly with stringed instruments. And incidentally, I almost want to restore the stock state of my amp just to refresh my memory, because with the current setup I feel like I've found the missing low end detail.
    • Burnin? Any concern that things might sound a bit more refined a couple hundred hours in ?
     
  5. willsw

    willsw Friend

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    The MicroZOTL bass has been an issue for many since the original iteration (the treble I haven't read about, and until recently hadn't heard about it in reference to the new one), and both the original and the successor were designed by guys who don't really listen to headphones and aren't that into tube-rolling. Interesting choices for manufacturers, but the ZOTL design is unique (and patented) and having it available as a headphone amp is worthwhile. This go-round, at least, we want to address the issues of the original if we can, and make it a better amp. Detailed reviews like this are helpful. The hard part is figuring out how to improve specific elements by working around this fixed board (we would like to design another headphone-friendly ZOTL board with David Berning, but there are many limiting factors and a lot of time involved, so it's in the unknown future). Weight helps, and we'll soon have cases made of thicker metal and thicker, more secure faceplates (with more durable paint also; I believe the black units are now shipping with the new faceplates, though Purrin got one of the last of the original batch). We've tried different things like upgraded caps, which didn't seem to make any difference, and we have other upgraded material choices that we're planning on trying out while remaining within the low end of the "no-man's land", remaining at the same base cost, really - or same base price, rather. The linear power supply is an obvious, nearly necessary upgrade, and I wish ours wasn't $600, but that's out of my hands. We're currently trying to figure out tubes. We don't have any connections who can get us consistent NOS options, and consistency and availability are very important to us, so it's current production. We have several tester tubes in our next tube order to see if the combination with the bright Tung-sol 6SN7s can improve things. Success would be good, as these tubes could be integrated without adding to the price. We've also contacted the higher end of new production and need to discuss possibilities of how to offer these tubes, or if it would be worthwhile to push up the price in order to integrate them.

    So, yeah. If anyone has technical suggestions for things to alter or add in order to improve the limitations of this amp, we like to hear them. Several changes we've made have been the direct result of customer comments, public and private. I guess I just posted this long-ass paragraph to say that. Thank you for the review.
     
  6. Ice-man

    Ice-man Friend

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    Why were you using the hd600 and not the 650? Just curious.

    I'm guessing that you used the stock power supply and not an upgrades LPS, yes? (sorry if this has already been pointed out)

    Did your nit picks with the midrange present itself across all headphones that you tested with?

    thanks...
     
    Last edited: Mar 31, 2016
  7. hifi01170

    hifi01170 Acquaintance

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    @willsw

    I have planned to sell mine. But thumbs up for your feedback and how constructive this whole exhange is based on a level headed review by @purrin
    Having company representatives being this open to improve their product based on customer feedback is great and should be the norm.

    I'm not willling to spend too much on tweaks (like LPS, tube rolling, etc.) as the LPS is still a lot of money.
    Am a total noob with regards to tubes as well so without having any clue just to go through tube rolling doesn't sound like a good idea. What prevented me from heading this way is my amb M3 and how it sounds for a lot less. All these tweaks would have been to get the ZOTL 2 to sound "like" my m3.... for a lot more money... not a very rational approach.

    So I might still hang on to them a bit more just in case, some magic be done to provide some bass slam, take away the treble glare... for that I'm waiting feedbacks from trusted members.

    cheers,
     
  8. zerodeefex

    zerodeefex SBAF's Imelda Marcos

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    Wow. Marv has a mediocre subwoofer.

    Thanks for the review and thanks to you, @willsw for soliciting advice and engaging the community! I might like it better than Marv does, esp if it's a hint romantic.

    I'll do a Vali 2, CTH, NBM, MZ2, MZ2 + LPS comparison a d hand off the lot to @CEE TEE so he can add the used Zana Deux at the top end. I'll parallel the outputs from the LPS4 I have to get enough current for the MZ2. The stock LPS is 12V 3.7A?
     
  9. Ice-man

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    While the upgraded power supply seems to bring some real improvement, it also kicks the cost of ownership to a completely different level and those expectations would go up accordingly.

    I can appreciate that Marv reviewed the amp as is with no upgrades. And I also appreciate the honesty of the review. Well done sir!!
     
  10. willsw

    willsw Friend

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    12V 2.5A. There was a typo (I don't know how it happened, I wasn't involved until more recently) that had the first batch of cases marked 3.7A. There is still currently a typo saying that it's manufactured by Urban HiFi. One guy trying to do everything at once was basically the structure of the company before I came on.
     
  11. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I don't muck around anymore on sites like Head-Fi to see what people are saying about this amp, though I did get direct feedback from another individual that has one. He too was quick to point out the treble issues. Stock unit, stock PSU, as far as I know. He said he did like it a bit more with some tube rolling.

    Anyway, thanks for writing up a quality review!
     
  12. purr1n

    purr1n Desire for betterer is endless.

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    I can try with my shelf of various power supplies, but I don't know if I will have time. I need to find the right connector and I may not have one handy in my parts bin. I also wanted to keep the impressions limited to a unit that cost $1100 so that it stayed on the low-end of no-man's land / high end of value. My tube rolling comments you were referring to probably went more like this: "if you are going to roll tubes excessively, may as well roll transformers or caps too." I doubt I would have told people to replace their power supplies before rolling tubes, because power supplies are just another can of worms and such advice makes absolutely no sense.

    As for measurements, tube amps measure 100 times worse than chip based amps. This is why I put the disclaimer "don't go NWAVGUY" in the first sentence of the measurement post and also why I offered measurements from a similar type push-pull tube amp (except with OPT) as a suitable comparison. Ultimately, the question is what is the hearing threshold of distortion, not why does the distortion plot look bad. This is new territory for us and hopefully we will see more things that correlate to what we hear as more amp distortion measurements come about. I have higher expectations of the readership now and don't want to keep wasting my time reiterating points that should already be known.

    Only 20 hour burn-in. I didn't bother with this because there was no advice from the manufacturer and other owners haven't indicated that burn-in solved these issues. My experience with the effects of burn-in is that it happens faster initially, or at least the majority of the burn-in effect occurs early on with the process slowing down over time.
     
    Last edited: Mar 31, 2016
  13. steve

    steve Rando

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  14. purr1n

    purr1n Desire for betterer is endless.

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    Yup still doing it. Give yourself an avatar too so I can tell that you are not a "rando".
     
  15. bazelio

    bazelio Friend

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  16. steve

    steve Rando

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    Done;)
     
  17. steve

    steve Rando

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    I'm sure it's gonna be lots of fun. YGPM
     
  18. zerodeefex

    zerodeefex SBAF's Imelda Marcos

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    WTF, I didn't realize you guys were so close :).

    It'll be me, then @CEE TEE, then we'll ask Nick and Prashant about getting it into the pipeline for loaners.
     
  19. CEE TEE

    CEE TEE MOT: NITSCH

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    Yes- would like to try...thanks!
     
  20. purr1n

    purr1n Desire for betterer is endless.

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    Mini-meet!
     

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