Review: Linear Tube Audio (LTA) "Ultralinear" Amplifier

     The other day I was reading a review of Cecile McLorin Salvant’s new LP “Dreams and Daggers”. In it, the reviewer quotes America’s jazz statesman, Wynton Marsalis, who has remarked that Salvant is the kind of singer that only comes around “once in a generation or two”. A week or so earlier, I had spent some time listening to Salvant’s first major release entitled “Woman Child” and this session left me agreeing wholeheartedly. I’ve owned “Woman Child” for quite some time and played it often. But I never would have placed Salvant in the same company as Billie, Ella or Sassy. But as I sat there listening to her unique vocal style and talented backing band fill the room this comparison seemed quite compelling--even obvious. So what was different? This time Slavant was being presented by a pre-production version of Linear Tube Audio’s new ZOTL “Ultralinear” amplifier and what I was hearing reminded me of nothing that I had ever heard before in all my 30+ years of audiophile madness. Put simply, the ZOTL Ultralinear is by a wide margin the most transformative piece of audio equipment I have ever had the pleasure to use in my system. This amp is completely addictive--once you hear music through it you simply have to own it. Common audiophile wisdom suggests that you build your system around carefully selected loudspeakers. The ZOTL Ultralinear demands that you build your system around IT, which in this case means finding a pair of reasonably high sensitivity/efficient speakers that you greatly admire, pairing it with the ZOTL Ultralinear, and living happily ever after.
     For those who haven’t heard of Linear Tube Audio (LTA), they are a relatively new outfit located just outside our nation’s capital in Takoma Park, Maryland. Headed by Mark Schneider, who recently concluded a long and successful career as an engineer and product designer, LTA works in collaborative partnership with David Berning, who for decades has designed some of the most widely respected amplifiers and electronics known to music loving man. Mark’s mission is to bring David’s designs to life in the service of music, with the goal of reaching a broader audience of audiophiles and music lovers while providing first class product support.
  About a year ago, I visited Mark in Takoma Park, just as he was getting his retail shop (Urban HiFi) ready for business. I was there to hear the recently released ZOTL 10 and ZOTL 40, and though the listening space was chaotic and the rest of the gear unfamiliar, what I heard was very intriguing. Mark and I stayed in touch and I’ve been happy to get to know him as a warm, honest and straightforward person with a passion for music, product design and manufacturing. When I learned that LTA was working on a new “Ultralinear” design that utilized TV sweep tubes similar to those found in the legendary Berning ZH-230, I asked Mark if he would allow me an opportunity to “test drive” a pre-production unit in my home. That’s how I ended up falling more deeply in love with Salvant--and with Joni, and Mozart, and Adderley, and… get the point.
     I won’t say too much about the LTA Ultralinear design--I’m not really qualified to speak to such matters. I will say that it is, like all Berning designs, a Zero-Hysteresis Output Transformerless stereo amplifier that puts out nearly 20 watts per channel. It uses the aforementioned TV sweep tubes (of which there are many varieties which can be had for less than five dollars apiece) in the output stage, and smaller, more conventional tubes such as 12at7 or 12au7 in the input stage. Like the ZH-230, different input tube combinations can be utilized to adjust the gain and “critical damping” of the amplifier. I have no idea what input tubes were in the pre-production unit I used, but what I heard suggests they were the “right” ones indeed. The Ultralinear also features an advanced switching power supply that Berning has deployed successfully in some of his most cherished designs. Between the absence of an output transformer and the lightweight switching supply, the Ultralinear is an amp you can throw under your arm and carry like a football. Like the ZOTL 10 and ZOTL 40, the ZOTL Ultralinear can be configured in monoblock pairs with the flip of a switch, thereby increasing the output by roughly 70%, so approximately 35wpc. Production models, which should be available very early in 2018, will feature casework by Virginia artisans Fern & Roby. LTA has set the retail price for a single stereo amp at approximately $6500.
     I am compelled to say a little bit more than a little about the sound of this amplifier. The first thing I noticed about the Ultralinear, and I “heard” this quite clearly with the ZOTL 10 and ZOTL 40 in Takoma Park, is the ridiculously low noise floor. This amplifier is completely silent. In fact, I had no idea just how “noisy” my previous amplifier was until I heard the LTA in my system. It was then that I realized just how much noise matters--and not just during quiet passages or small scale performances. The pitch black background of the Ultralinear represents the foundation of its superlative performance. It is, in part, what makes this amp so unique and explains, to some degree, the other intoxicating characteristics of this amplifier. Emerging from this total blackness is the sound of real music, played by real people, on real instruments--not a facsimile or close approximation--the real thing, in your room, in a way (I’ll bet) you have never heard it before. I, for one, have never, ever heard it sound so right and so real. Not in any system that normal, crazy audiophiles with kids and a mortgage could actually afford.
     The other thing I instantly noticed is how the pace, timing and rhythmic flow of musical performances are scrupulously rendered. During my time with the Ultralinear I listened to Mozart's Divertimento K.563 for string trio (Meridian, The Cummings String Trio). I’ve heard this disc a thousand times--always a joy but on this occasion the instruments of each performer were so thoroughly intertwined that I was transfixed. Through the Ultralinear it was much easier to appreciate the collaborative energy of the trio, with each musical line, phrasing and emphasis vividly portrayed. For the first time I could hear how each member listened and responded to the others, giving the piece a more spontaneous and natural feel. The piece ended and I had no idea where I was or how much time had passed. The experience was totally immersive and my mind laser focused throughout on the interplay between cello, violin and viola.
    This preservation of subtle timing cues and dynamic shadings got me thinking about a review I had read years ago by Art Dudley on the virtues of Naim electronics. In his review, Art spoke about the way the Naim equipment tracked Joni Mitchell’s vocal gyrations on the cut “California” off the album “Blue”. So out came my copy (the recent Warner/Asylum reissue--excellent!) so I could give it a spin with the Ultralinear in control of my loudspeakers. Wow! On the strength of Art’s review I purchased a complete Naim setup back in the early 1990s (140/62/HiCap) and enjoyed the “PRaT” factor provided by this gear for half a decade. But that Naim setup has nothing on the LTA Ultralinear. Not only was Joni present in the room--bathed in a warm, three dimensional glory--but her singing style and vocal prowess was communicated in breathtaking fashion with all her subtle dynamic shifts and trademark stylistic touches brilliantly revealed.
     With the LTA in my system I also came to appreciate the importance of transient fidelity, something that Michael Fremer has long gone on about but which I’ve never fully appreciated. For example, I played the recent reissue of Nick Drake’s “Pink Moon” and found his guitar work exceptionally fluid and alive. Transient energy, particularly the leading edge of acoustic guitar strings, are so lifelike it is spooky. Small shifts in dynamic intensity are suddenly revealed as clear artistic choices that are essential characteristics of the performance. So are timing and syncopation, which reveal a sophistication that is utterly mind boggling. Leading edges are so faithfully portrayed they can startle, such as with Aaron Diehl’s piano on “Jitterbug Waltz” from “Woman Child”. On the opposite end, the decay of well recorded piano fades as slowly as a midsummer sunset into the inky blackness of the Ultralinear. This combination of correct timing, dynamic agility, and transient reproduction were revelatory, transforming albums that I thought I knew like the back of my hand into wild rides, serene journeys or sorrowful interludes.
     Finally, and I am saving perhaps the best for last here, I was completely blown away by the spacious soundstage this amp produced. It transformed the soundscape, adding multiple layers of depth and copious cushions of air around the performers. Everything became completely three dimensional in a way I have only heard in rooms that allowed for a much better setup than mine. It is this type of spatial realism, when combined with such vivid, realistic tonal color and transient fidelity, that makes the Ultralinear so intoxicating--so NECESSARY.
     Those of you still reading may be wondering about the tonal qualities of the LTA. Does it sound like tubes or solid state? Is it warm and fuzzy or lean and clean? The best answer is….neither. In my system the Ultralinear conveys the natural warmth of acoustic instruments and voices without editorializing. It is exceptionally clean, quick and dynamic yet completely uncolored and free of sonic artifacts. When you listen through this amp your focus will be squarely upon the music, not the means (transistors or tubes) by which it is being reproduced. Thus, in deciding whether to choose this amp, you can set aside system matching concerns that relate to warmth and color--the typical ying and yang considerations--and focus instead on the simple question of whether the amp has sufficient power to drive your speakers. And on that score I would encourage you not to let the relatively low power rating scare you off--the unique ZOTL design topology suggests a very robust 20wpc, and my listening experience (albeit with quite efficient speakers) bears this out.
    Like many audiophiles, I’ve been at this a while--nearly 30 years now. During that time I’ve seen lots of products come and go, many lauded by reviewers as “groundbreaking” or “SOTA” designs that fade from view rather quickly. However, there are a select few that have, for good reason, captured the imagination and commanded the respect of music lovers throughout the world and, as a result, have stood the test of time. I’m here to tell you that the LTA Ultralinear will likely join this selective group. Like Cecile McLorin Salvant, the LTA Ultralinear is the kind of amp that only comes around “once in a generation or two”. Paired with speakers of moderate to high sensitivity/efficiency and partnered with capable source components, the Ultralinear is simply a revelation in home audio reproduction. I’m on the list for two and these will be the last amplifiers I will likely ever own.

Room: 13 X 17 X 8 with openings in the corners behind the speakers. No room treatment or equalization.

Associated Equipment:
Speakers: Daedalus DA-1.1 AP/V2 with Soundocity Outriggers and Trim Rings
Amplification: Herron VTSP-3A RO3 Linestage
Phono Stage: Herron VTPH-2
CD/SACD: Esoteric X-O3SE
Turntable/Arm/Cartridge: VPI Scout “Supreme”/3D-10 Gimbal/Soundsmith MIMC Star
Power Cables and Interconnects: Empirical Design
Speaker Cables: Dynamic Design Lotus Series

@morganc Hey there. Either the ZOTL10 or the Ultralinear will have plenty of power for both of those speakers.

@dodgealum is right, we've shown with the Spatial M3 Sapphires at CAF and FLAX, and we had those speakers in our shop for many months.

Paired with the Z10 Integrated (same audio circuit as in the ZOTL10 power amp), this combo received "best sound at show" and many other plaudits from reviewers and consumers alike. I'm sure others on Audiogon were there and can tell their first-hand accounts of the sound. The ZOTL10 is based on EL84 tubes and has a neutral and maybe slightly sweet (due to the tubes) sound. I had a reviewer tell me the sound was hard to describe, but it was so uncolored. I consider that a great compliment, as we're trying to present the music as naturally as possible.

Likewise, the pairing of LTA and Tektons is also well known and well regarded.

The Ultralinear has a shorter feedback loop than our other amps, and this (among other things) makes it our most detailed amp. I was listening to a Cannonball Adderley track with a customer a couple days ago, and it was almost like you could hear the individual tines of the drummer's brushes on the snare. It is a very refined sound, less forward than the ZOTL40, and very pleasing to listen to over long periods. It's often compared to SET amps in it's representation of detail.
The Z40/ZOTL40 Reference is an EL34-based amp has a much more forward presentation, wonderful midrange, but offers less detail than the Ultralinear.

We consider both the Ultralinear and the ZOTL40 Reference "flagship" amps. That's why they are the same price. One is not objectively better than the other, it's just a matter of what sound you're going for, or in some cases, how much power you need. I took both to customer's home yesterday, and he preferred the ZOTL40. The previous day, a customer (the one mentioned above listening to the Cannonball Adderley track) in the shop preferred the Ultralinear. That's how it goes - it's about 50/50.

Per conversation with Mark I upgraded the tubes in the MZ3 and UL. Brent Jessee gave me recommendations labeled as "good" and "best". Based upon my desired sound preferences, the sound coming from my Tekton Double Impacts with the "good" tubes is tonal neutral. I so appreciate the not so forward sound of the UL because I listen to music four to six hours per day. For sure kudos to the LTA staff who are always very responsive, informative, and not "sales pushy".
After probably a year of reading review after review about the UL, I finally took a chance to audition it in my house on my speakers (Spatial M3 Triode Master).  Seeing all that was said about it's comparison with other amps, LTA or otherwise, I was simply too curious to not hear it at some point.

In short, I'm glad I did but I also sometimes wish I could leave well enough alone.  I feel like that's a common symptom of our shared disorder.  

Even on a frozen cold amp, music came out swinging and was immediately very distinctive compared to the LTA Z10.  I let it play all day while I worked to get up to temperature and break in a little.  When I got my Z10, I had to cover the rear facing side of the open back tweeter because of a little too much treble energy which eventually smoothed out enough to remove the cover about 3 months later.  I expect to have to do the same with the UL since it's a little much early on.  After about 6 hours of warming up, I sat down to run it through some old standards and was taken aback by how much more was coming through compared to the Z10.

The Z10 has a lot of great things going on.  Super smooth, dynamic, clear, and spacious with a decent bass, palpable midrange imaging, and open extended treble.  The UL takes these a considerable step further.  Bass lines that were impressive to be handled with 12 watts are incredible on the UL.  So much stronger control and dexterity around transitions between bass notes, the attack and decay on them, and the depth to which they go without getting flabby or loose.  I typically don't listen to classical on the stereo since it's not been incredibly engaging.  Not so with the UL.  The bass drum pounds were startlingly real (scared my dogs) on O Fortuna and individual singers could be picked out among the choir.  Classical now sounds VERY engaging and captures the ebb and flow of a symphony way more like a live performance than the Z10 could do.  Illustrating the bass was instrumental to that effect and the UL does it extremely well.  I had hooked up the speaker level outputs to my sub on the Z10 to get a bit more bass heft....not needed with the UL at all.

The midrange gains even more space and texture, with an effect I can only describe as almost wrapping around your head slightly rather than being projected at it.  Imaging is still spot on, but the width and depth expanded by a sizeable degree.  Ethereal effects and background instruments envelop and surround you like being on the front row.  So much of what I (and most folks it seems) enjoy exists in how well midrange is reproduced.  Voices, guitars, etc. get more real and show more of what the artist intended when it is skillfully amplified.  The LTA makes it all more real and more "reach out and touch it".

The top end is airy and extended as well.  No tube roll-off...even though my ears might prefer a little of that.  So much clarity and space it (like other reviewers have said) makes other amps sound broken for how much noise and distortion they introduce to dull this reproduction with transformers and other noisy components.  The UL (and the Z10) strip this away so effectively, it's forehead-slap inducing.  I assume that as with the Z10, more break in will smooth this out even further and just get better over time.

Some other slight differences between the Z10 and UL are that the UL tubes glow a little brighter and hotter and that the UL volume control relays are a little quieter when you click the volume around.

All in all, the UL's bass and midrange performance even on my already sensitive (95db) speakers showed me that though 12 watts is "enough" with the Z10, the extra oomph provided by the different circuit and slightly higher wattage isn't insignificant and worth the audition of the UL if you have the chance.  

DAC - MHDT Orchid
Source - Bluesound Node 2i streaming Spotify