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

Nice, thorough review, well thought out and organized. Good read! Thx @dodgealum!
Thank you for a beautifully written review. After that read I would be looking to buy this wonderful amp if I didn’t already own one. In the short time I’ve had it I can agree with everything you’ve said. A benchmark in audio history.
Wow. You beat me to it and described the Ultralinear better than I ever could.

I live in DC and found out about LTA last year. After contacting Mark he agreed to bring a MicroZotl and a Z10 to my home for an audition. Pretty amazing service. At the time I was using a custom made 01A DHT preamp and a First Watt SIT2 amp. Not too shabby but after hearing the LTA equipment I sold both and purchased the MZ2 and Z10. I am using Omega Audio High Output Alnico speakers which are 97db.

At some point early on Mark showed me a raw version of the David Berning designed Ultralinear amp with the cool 17JN7 Compactron tubes. I told him to let me know when it was finished so that I could try it. In December he gave me a pre-production model to audition. In a word I was dumbstruck by it's truly magical sound. It was so transparent and dynamic that it took me a while to adjust. It worked perfectly with my Omegas. It was clear that I would buy one. Over several weeks I worked with Mark to tweak the circuit a bit. He probably made 10 trips to my home. I now have my own Ultralinear having chosen to receive it early in a case similar to the Z10/Z40 and not wait for the more upscale Fern and Roby case which will be used for production.

I cannot recommend this amp more highly or the service and care I received from LTA.
Thanks everyone--it is very affirming having others that have experience with this amp reporting the same results. Mourip, very cool that you were able to see how the design evolved into its final iteration. The pre-production unit I auditioned was fully formed (i.e. identical to what will be released shortly in the F&R casework) so we all owe you a debt of gratitude for your involvement in the development process. I'm not familiar with the 01A DHT but do know the SIT-2 by reputation. I think it says quite a bit about the LTA Ultralinear that you felt compelled to sell the First Watt to own the LTA. That amp is considered by many the holy grail of low power SS amps. That the Ultralinear clearly bested it in your system is testament to the quality of the LTA. I, too, was "dumbstruck" when I first fired it up in my system. My first reaction (and it was dead cold and had zero break in hours) was "what the hell is going on here?" and my second was "what the hell is wrong with the amp I've been using? -- which is an EXCELLENT amplifier and nearly twice the cost. The LTA is THAT good--I hate this phrase, but the Ultralinear is truly a "game changer".  
Hi dodgealum -

Many thanks for your fantastic review!  Well done!

As a Linear Tube Audio and David Berning dealer...we were (and still are) as excited hearing the ZOTL technology as you explained in your review.  We have every LTA product except the Ultralinear, which will be coming soon.  I was interested to hear the product from the start...but you just turned that interest up about 4 notches to get my hands and ears on the ultralinear! 

Audio Archon - dealer
Hi Dodgealum - 

Thanks for your comprehensive and well written review.  I see by your associated equipment list that you are pairing the LTA amp with a Herron preamp.  Did you audition the amp with a LTA MicroZotl preamp, and if so did you feel that there was an improved synergy with their preamp as compared to with your Herron?

@weebeesdad , I can confirm that the synergy with the MZ2 is outstanding. I don’t currently own another preamp for comparison but the MZ2 is so good with the UltraLinear I’m changing a thing.
@weebeesdad, I did not get a chance to try the Ultralinear with the MZ2 and used it exclusively with my Herron VTSP-3ARO3. My understanding from the forums is that pairing ZOLT technology in the pre-amp and amplification stages provides unmatched synergy that elevates the performance of each separate component. I understand LTA will be releasing a full featured pre-amp with F&R casework to match the Ultralinear at some point in the near future. Once released this will certainly be something that I will want to consider. For now, the Herron is the best linestage I have tried by a wide margin and the sound it produced with the Ultralinear was sublime. 
Dodgealum - It would be interesting to hear what your impressions are should you get a chance to audition the MZ2 with the Ultralinear.  I have a MZ2 which I bought, and love, as a headphone amp. When used as a preamp, however, I still prefer my Dehavilland Ultraverve which seems to have a bigger and bolder sonic signature. I use it with a pair of Dehavilland mono blocks where I would expect the synergy to be to its advantage, however even with my two solid state amps I generally prefer it over the MZ2.  Of course, when mated with the Ultralinear the LTA pre may be preferable.  The Herron certainly is an excellent preamp so the MZ2 may or may not be an improvement.  Do keep us posted if you get the chance to audition the LTA preamp...

Thanks for your review.  I contacted LTA about availability have not heard back yet.  Do you have any update on availability?  Thanks
Hi Bob:

I haven't but it will be soon. I'll touch base with Mark and see what information he can provide.

Well I have narrowed my next amp down to a LTA or Pass xa25.  I have been a tube guy forever but the Pass is sure tempting.  Mark has indicated the Ultralinear will be available very soon and he is going to forward me a picture of the production model when it is available.  I am leaning towards the LTA and will order one of these fine amps within the next few weeks.
bobheinatz: I sent the pre-production unit back to LTA after spending several weeks with it in my system. Like you, I am waiting for the production model to be released, which will happen soon. Over the past several years I've considered several different low power tube and solid state designs including those from Pass, Modwright, etc. but am completely confident that the LTA Ultralinear is the best possible choice for me and my system. Though I have not had the opportunity to try them all, I simply can't imagine anything sounding better. I'll wait patiently for the LTA to be released and enjoy a long ride with these amps!
I just placed an order for this amp (in the pre-production ZOTL40 case).  Offer was too good to refuse.  Mine will be retrofitted with remote volume control, and supposedly works very well sans extra preamp.  I only need 1 input anyways (from DAC).  The F&R cased production model will have no volume control available.  I'm planning to use this amp in a 2nd setup, but in the meantime, I will listen to it vs. my Berning Quadrature Z monos in my main setup.  Let's see how the little LTA stacks up :)
Cool--that should be an interesting comparison. I'm curious as to what speakers you are using in your main system given the power output differential between the Quadrature Z and the LTA Ultralinear. Given the enormous cost differential, it will be interesting to see how the LTA competes, particularly if the speakers present a reasonably easy load. Keep us posted!
Hi guys, since I have heard both Quad Z and UL Amps I can say they have a similar Berning house sound even though I have not heard them driving the exact same speakers. Personally I think the UL is every bit as good if not better. Of course the Quad Z has the power to drive any speaker made. Keep us in the loop Kathir.

Hi Lance, yeah, I will keep this thread posted.  I'm not much on posting very often, but I feel I should contribute/give back from time to time, since the internet rewards me with so much information when I need it.

For others out there, I'm not planning to replace my Quad Z with the UL.  I'm going to use the UL in a 2nd setup that does not require much power (at least I'm not intending it to).  My main setup, which employs the Quad Z's, consists of NOLA baby grand ref 2 speakers.  The speakers are designed to provide an easy load to tube amps in general, but their efficiency is low-ish at around 87dB.  This will mostly be an experiment, just to compare/contrast at reasonable volume levels.  In my main system, I'm using an LTA MZ2 as a preamp (which I will keep in place for the comparison), and I am using an Aqua La Scala mk2 DAC being fed by HQplayer via USB as a source.

My 2nd setup has a recently acquired NOLA Brio Trio speaker system.  Still sorting out what DAC I will use in that setup (TBD).

I won't have the UL for at least a couple weeks.
Hey guys thought I would check back in...I decided to go with a monoblock pair of the pre-production model which is housed in a ZOTL 40 case and includes the volume control for direct operation (without preamp). I've had one of the two amps in place, running it stereo, for the past few weeks. My impressions are unchanged. All I can say is that this amp is off the charts--well beyond anything I have heard drive my Daedalus speakers and producing in my system some of the best sound I have heard anywhere, anytime. Listening to the Ultralinear is a mind blowing experience--I can't imagine my system sounding any better but am going to go mono nonetheless to see what the additional power will do. For those able to get to Axpona this weekend, I would love to hear your reaction to the Ultralinear/Daedalus Apollo 11 pairing that will be featured in one of two Daedalus Audio rooms. Should be amazing. The monoblock pair will be the end of the line for me in terms of amplification--the UL is that good. 
@dodgealum   Appreciate the update. Happy that you are ecstatic with the performance! 

It will be great to get additional feedback from the LTA/Daedalus rooms at Axpona.
I am still very happy with my UltraLinear. LTA now has their new MicroZotl preamp showing on their web site. I hope to have one in the house to try soon. Based upon what I have heard from Mark at LTA it should be a nice upgrade from my MicroZotl v2.
Since no one else has offered yet, I was able to attend Axpona to see the Lampizator/LTA/Daedalus room. Like most shows the room was too small, but hearing through this the sound was excellent. Top to bottom it was everything I was looking for. The dual mono UL’s drove the Apollo’s with authority. Apply any of your favorite adjectives. I especially liked the integration of the mid-bass and low end. The speakers are beautiful to look at as well. Rich. Classic. Craft. Just need to determine what to acquire first. Lou liked the Apollo 11 with the UL as well.
The other room with the MZ2 mated to a stereo UL sounded great too. I’d take it over my MZ2/PassXA30.8 pairing that I currently have. May not be a coincidence that both amps have the same retail price.
tuckia08: Did you get to hear the Apollo's in Lou's other room with the Modwright Ambrose A30's? I'd be interested in hearing how you would compare the sound in these two rooms. I hear the Apollo's are very special and may work better in the small rooms that are typically found at these audio shows.
In my room the UltraLinear is the best amp I’ve ever heard.

I am now beta testing the new LTA Micrzotl Preamp and it is proving itself to even better than the MZ2.
Agreed. I had the new preamp in my system last week for beta testing also and it is much better than the MZ2 which is saying a lot. I am using it with the LTA Ultralinear amp. Remarkable clarity and dynamics.
Dodgealum: sorry I was out and about for a bit.
I did briefly stop in the Modwright room with the Apollos, and maybe this isn’t a fully qualified opinion because of the brief visit, but the LTA room was doing it for me and the Modwright room was not. I wasn’t sure which amps were playing however. My impression at the time was that the front end and amplification were the main differences. 
I heard from someone that the best combination may be the Modwright Ambrose preamp with the LTA Ultralinear. I highly suspect that either Apollo will do the job. I’m probably going to order the Apollo 11’s in the next couple days, and then wait. With such an outlay I’ll have to live with my MZ2 and Pass XA30.8 for awhile, but I don’t think I’ll be suffering too much. I really think the Ultralinear is a slam dunk with speakers of adequate sensitivity. What I heard was transparency, speed, PRAT, body, texture, and detail, in spades. I bet the Lampizator was a factor in all of this too.
Hi All,

This is a follow up on my listening impressions of the UL in comparison to David Berning Quadrature Z mono blocks (200W).  I got through this testing a while back, but just never got around to posting my observations.  Just to refresh, I plopped in the UL (single unit, stereo) in lieu of my QZ's (no other change to front end or speakers).  The rest of my setup consists of the following chain:  HQPlayer (USB PCM) -> Aqua La Scala mk2 -> MZ2 -> Amp -> Nola Baby Grand ref 2.

I believe I let the UL sufficiently burn-in before forming my final opinions, although I did not notice very much change over burn-in (there was a little more ease and space after many hours of use, but not as much as I was expecting).

Long story short, the UL falls short of the QZ, but not necessarily in the ways that one might imagine (related to high SPL and dynamic range).  In fact, for my listening comparison, I would say I kept the listening levels low (<80dB SPL) to be fair.  The volume was well below the maximum for the UL (I used the direct volume input on the UL to bypass the high quality relay based stepped attenuator and used the MZ2 volume control instead, same as I do normally in my setup).

Here are some details.  The UL excels in the bass department.  I think a number of people on this thread will note the nice bass response of the UL.  Surprisingly, bass wakes up nicely with the UL compared to my QZ.  Go figure.  Its not about the power!  Bass is tight and powerful, well defined.  Leaves me lacking more from the QZ..

The mids on the UL have a bit more tonal weight than with my QZ.  This is a nice plus.  I guess this could be flavored by some tube rolling (either amp).  I did not tube roll any of the stock tubes in the UL, whereas my QZs have some nice NOS Siemens tubes in them (known to be a little "thin" on the mids).  I give the UL a plus here.

UL is a lot more quiet in the background (a lot less hiss with volume at max).  Better SNR is a plus.

I personally did not like how the UL was a lot more forward in its presentation than the QZ.  I found this irritating, and for me, detracted from the overall positive attributes I previously mentioned.  In addition to being more forward, the stage size was markedly reduced in both width, and depth.  I lost the "immersion" and "holographic" feel of the music.  The UL's presentation, although nice for vocals, was just not up to the task of convincing me of a real 3D performance like the QZ could (especially at night with the lights out).  Big difference for me.  Because of the lack of space in the sound stage with the UL, I could better localize the sound coming from my speakers with my eyes closed (bad).  I cannot do this with the QZ.  Overall, there is a lack of spaciousness and "air" in the body of the sound stage (nothing to do with the treble, for which the UL does just fine).  This is difficult to describe because the UL appears to have slightly more subtle details available in the treble (probably due to the blacker backgrounds), yet details (layers) that would normally fill a 3D sound stage are just not there with the UL.  My personal feeling is overall, the sound is lacking emotional connection compared to my QZ, although there is nothing that is "off" (tone is right, lows, highs, its all there).  The QZ, although its a "muscle" amp, plays with supreme finesse down through the first watt.  It seemingly outclasses the UL in this first watt of output power, adding more realism to the performance, and then continues to pull away beyond the first watt.  The QZ layers music so well.  This aspect is tough to beat.

Overall, the sound felt a bit more "stuffy" and congested with the UL.  It felt like listening to a more dynamic range compressed CD than when played through the QZ.  Things got worse when I cheated and turned up the volume a lot more.  The UL's congestion became a lot more apparent (harsher mids/treble).  I can't get the UL to play loud comfortably (for me).  But then again, I wasn't expecting this.  The UL is fast (dynamic), and it performs admirably when pressed (much better than I expected).  Both amps share a lot of the same DNA, so it is more like comparing the two amps, rather than contrasting.  I believe it is unfair to compare the UL to the QZ at higher SPLs.

I think a little bit of tube rolling in the UL can yield some very tangible improvements (although I have yet to try).  From personal experience with tube rolling other gear, I know tube swaps can sometimes yield more spacious presentations.  I think the UL can only get better from here.  My comparisons were in no way made to detract from the overall enthusiasm of the UL.  In fact, writing such a comparison to an amp that is multiples of the UL's price actually is a testament to how great of an audio value the UL is.  It can hold its own.  For paying a lot more with the QZ, there are tangible benefits, but those benefits may not be worth the price difference for some.  I'm very happy with both amps!  Please also consider, that my audio priorities may be different than yours, which is why I tried to list positives and negatives.  Only the reader can discern if what I like or dislike is important to their ears.  In conclusion, even though my write up appears critical, please take it as an endorsement for the UL.

Manthik thanks for doing the comparison with the QZ monoblocks and sharing your listening impressions. I have not had the pleasure of hearing the QZs but know they are reputed to be among the best amplification available at any price. Your conclusions are very interesting and surprising. I find it particularly surprising that the UL produced higher quality bass in your system than the QZs. Given the power disparity, that is extraordinary. Your observations noting a diminished soundstage, loss of dimensionality and congestion is not entirely unexpected, given the load your speakers present and the fact that you were running the 20 watt UL as a single stereo amp. I wonder whether a pair of ULs would have cleaned things up a little and provided a stage more akin to what you hear with the QZs. I know your speakers well, having heard them with a pair of VAC Statement Monoblocks which have a similar power rating to the QZs. They really made the Nola's jump and the soundscape was quite impressive. I wonder whether, even at low volume levels, your speakers require a bit more than a single UL can provide. Used with a benign load--my Daedalus are 97db sensitive and present a pretty stable 6ohms--I find the UL very uncongested with excellent differentiation of instruments on a broad/deep stage. It would be great to see reports on the UL from people using it with other speakers to see just how versatile it is. My sense is that when used with the right speaker most folks will find it a phenomenal amp but that it should be used within the constraints intended. Thanks again for sharing!
Nice review Kathir, it’s funny you need to put 32K mono blocks up against the UL to make it a fair competition. I love it.

hi, may i ask what are the special traits that LTA preamp have that make you sell off a DHT preamp? i looking at Coincident Linestage for another setup and now it seems there's a serious contender at much lesser price.. any comments would be much appreciated 

Charles, have you heard any ZOTL products before? 
Thank you everyone  : -) 
I am not sure if the first of the new Micro ZOTL preamps have started shipping yet. I don’t have mine yet but my short time with a Marks preproduction unit was impressive. I think it can compete with much more expensive preamps. You should call Mark Schneider and talk to him. He has a 30 day trial policy.
Can anyone make some direct comparisons between the UL and any good/great 845 or 300B SET/PSET amps (mono or stereo)?  These reviews in the thread are well written, but it's hard to discern where this amp would really stack outside of the ZOTL extended family without some broader comparisons.

I have an MZ2 with NOS tubes and I enjoy it a lot--it's serving as a pre in one of my systems, and it's quite solid as an integrated/pre/and or headphone amp (it's truly an outstanding value by all rights), and I believe it sounded better in most configurations than my First Watt SIT2 by a little bit (the SIT2 having been previously mentioned ahead in this thread).  I'm not surprised to hear some mention the UL is better than the SIT2, as I assume it's better than the MZ2 as well (which in turn, to me, is better than the SIT2).  However, as positive reviews as the SIT2 has received, I personally don't feel it to be as outstanding as claimed (I owned it for 4 years and compared it to about 10 other amps on 4 sets of speakers during that time).

However, at $6800 for the UL, you're getting into some decent SET amp money, especially on the used market.  I would love to hear if some have had some direct experience they could discuss.

yes, good questions. Since I don’t own a 300b or an set I can’t say but the UL is better than my ZOTL40 and MZ2. I too am curious so if anyone nearby has a 300b or Set I would love to do a mini shootout.

Have UltraLinear will travel.
Update--I moved and decided not to go with the monoblocks in the shoebox case. Instead, I decided to stick with a single stereo Ultralinear in the new Fern and Roby case and upgrade the 12AX7s to Amperex "Bugle Boys" as per Mark's recommendation. I made a number of other system changes and am in a new listening room so cannot comment on what the Bugle Boys are doing but will say that I am still loving my UL paired with the Daedalus Apollo's. Mark and his team are such a pleasure to deal with and the after sale support is off the charts. Kudos LTA.
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Can any of you compare the UL to the Zotl 40 and/or Zotl 10?  

I'm driving HIgh Efficency speakers and have owned a Berning amp in the past and loved it.  

I'm intrigued by the reviews and know one of these amps is what I'm looking for and wanted to hear from anyone who has had the chance to hear them side by side.  
@morganc I have heard them both, but I also work at LTA, so you probably want to hear from someone else. :) That said, I'm happy to answer any questions you have, publicly or privately. I won't chime in unless specifically asked, though. I don't want to hijack the thread.

@lancelock is very familiar with both of them... :)

I own a ZOTL40 and Ultralinear.  They are very similar sounding for the most part. Most noticeable is the bass in the Ultralinear is even tighter and deeper which is hard to believe since the ZOTL40 has incredible solid state like bass. For me it would depend on the efficiency of my speakers. If you need a few extra watts the ZOTL40 is the way to go but if not it doesn’t get much better than the Ultralinear.
Thanks @lancelock That is great info.
And thanks @ntolsonCan either of you also compare the ZOTL10 to the Ultralinear?
I am likely to be driving either Tekton Electron SE's or Spatial M5's, so I do not need a lot of watts necessarily, though I know sometimes headroom and extra power is very desirable.

@ntolsen may be your best bet here—LTA regularly shows with Spatial so he has probably run the various LTA amps with the M5’s. Also, from what I understand LTA has enhanced the latest ZOTL 40 (aka the “Reference”) such that performance comes very close to the Ultralinear, though if you don’t need the extra watts the UL is still the best in the lineup. Call Mark at LTA—super guy who will help you make the right choice.
@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