Linear Tube Audio ZOTL40, microZOTL Pre | REVIEW

“These ‘uns are a little bit different,” Scot Hull told me in that almost impenetrable Northern Maryland drawl of his. It was almost a warning—he knew I loved the Linear Tube Audio Z10 integrated so much that I gave it an Editor’s Choice Award, and that the LTA ZOTL40 power amplifier and microZOTL preamplifier were cut from a slightly different cloth when it came to the overall sound. The Z10 was agile and exceptionally light on its feet, and Scot believed—after spending some time with the separates—that they were meatier and presented a different skill set.

I had no problem with Scot passing the baton to me. I’ve heard so many of Linear Tube Audio products now that I can barely contain my enthusiasm for this brand. One of the biggest reasons why I agreed to this review was that I’ve just received the Fern & Roby Raven IIs, and after my review of the larger Ravens with the Z10 I’ve discovered that the matching of these two brands’ speakers and amps represents one of the most synergistic couplings you’ll find in high-end audio.

There was only one problem. The Z10 seems like a better fit with the Raven IIs—this is the “entry-level” system that Christopher Hildebrand sells at his Fern & Roby showroom, along with Black Cat Cable from Chris Sommovigo. We’re talking about a $4950 integrated amplifier paired with a pair of small single-driver “bookshelf” speaker that retails for $5750/pair. (They’re actually more than just bookshelf monitors, but you’ll have to wait for that review to see why.) I almost felt like I was testing these four components in reverse—maybe the ZOTL40 ($6800) and microZOTL preamplifier ($4450) were more suited for the big Ravens, which cost $9500/pair.

But as I found out, it doesn’t matter. The magic forged between these two companies is undeniable in any combination. Best of all, the ZOTL40 offers 46wpc into 8 ohms, and 51wpc into 4 ohms. That means I could try out the Linear Tube Audio separates with a greater variety of speakers—the Z10 has only 13wpc, albeit 13 absolutely mesmerizing ones.

Wait a minute—did I just break one of my reviewing rules that you should never begin with the story of how you were assigned a particular product? Dammit. Oh well. Perhaps this is where I should tell you that there’s no such thing as a Northern Maryland drawl, either.

The Linear Tube Audio zotl40 Reference Power Amplifier

The first thing you’ll notice about the Linear Tube Audio ZOTL40 is how light it is. Officially it’s 15 pounds, but after lugging that McIntosh MC2152 around for a few months it felt like nothing. That, of course, is due to its lack of power transformers in this classic David Berning circuit, but the ZOTL40 feels like it’s an empty box. Even though the chassis is larger than the Microzotl preamplifier, it’s lighter. Than the preamplifier. You read that right.

It’s even lighter than the Linear Tube Audio Z10 integrated, but that’s because the Z10 has all those preamplifier thingies in it. It’s a good thing the amp has plenty of vents on the top plate so you can peer into it and see circuit boards and tube sockets and know that it will probably work when you flick the big switch on the front panel. Even my dog Lucy, who usually gets out of the way when I move heavy amps and speakers around, seemed very curious about the ZOTL40 and kept peering into it. “Is it broke, Dad?”

Perhaps that’s why the ZOTL40’s power rating is so surprising, and so welcome. Sure, the ZOTL40 spent most of its time here hooked up to the 94 dB Raven IIs, but I also had tremendous success using it with the Trenner & Friedl Osiris speakers, which have a sensitivity of 88.7 dB, albeit with a friendly 8 ohm impedance.

The ZOTL40 uses four EL34s in the output stage, along with two 12AU7s and 12AXTs elsewhere, but these aren’t just any EL34s. They’re a matched quad set of NOS Mullard EL34s, known for their warmth and their nearly perfect midrange. At the same time, Linear Tube Audio’s ZOTL designs are known for their ability to provide plenty of detail as well as a very linear frequency response. At no time did I feel this amp short-changed the highest highs or the lowest lows.

The LTA MicroZOTL Reference Preamplifier

The Linear Tube Audio microZOTL preamplifier operated almost exactly like the Z10 integrated. All the buttons were in the same place, and for the most part the features were identical. (Refer back to my review of the Z10 for an in-depth survey of everything it does.) Linear Tube Audio has improved this version over previous designs by using a new chassis that, along with the ZOTL40, was manufactured by Fern & Roby. It’s less resonant than before, and much more attractive than the first generation of Linear Tube Audio amps. (The Z10 also sported this cosmetic upgrade.)

In addition, Linear Tube Audio states that several improvements were made such as “new circuit board material, new volume control technology, upgrades in wire, capacitors, tubes, [and] linear power supply,” and this creates a much cleaner and clearer sound than before.

Finally, I should mention the headphone amp on the microZOTL. It’s superb, as you should expect–LTA makes some of the best dedicated headphone amps out there right now.


From the first few minutes of life with the Linear Tube Audio ZOTL40 power amplifier and microZOTL preamplifier, paired with then Ravens, I felt very much at home. With the Z10 and Raven combo, I noted “a stunning and realistic sound that gave me goosebumps.” The Raven IIs are very close in design to the Ravens—same SEAS Exotic driver, same cabinet construction but in a smaller enclosure. That meant that the bass was not quite as deep with the Raven IIs, but they made up for that by being far more easy to place in the room. (The Ravens need a little space around them and between them, but the Raven IIs tend to sound great anywhere you plop them.)

Scot Hull was correct in his assessment of the overall sound of the ZOTL40 and the microZOTL. He remarked that the sound was just a bit darker than the Z10, but I think that’s grading on a sliding curve. The Z10 is very light-footed, and perhaps the separates are closer to neutral—if that’s what you want. There is more meat on the bone, but it doesn’t come at the cost of clarity or detail.

What the Linear Tube Audio separates didn’t do was subtract from the unique, comfortable sound of the Raven IIs. Both Fern & Roby Ravens possess a laid-back, relaxed sound that opens up but still allows you to take in the musical structures as a whole. You get plenty of imaging and soundstaging, but there’s more interplay within the space, more interaction between performers and individual sounds. I used many of the same recordings for the ZOTL40 and the microZOTL as I did for both the Raven and Z10 reviews—MA Recordings’ Sera una noche, Lyn Stanley’s London with a Twist and several astonishing 2L Recordings releases. I still noticed all of the same strengths such as the very humane sense of warmth within the performances and the distinct sonic effects that come from a musician coupling his body to the instrument.

Moving On

After a while, I talked myself out of making more comparisons to the Z10 and the ravens, since they were no longer around. The Trenner & Friedl Osiris are close to the big Ravens in size and price, even though they sound very different from each other. With the Osiris hooked up to the Linear Tube Audio amps, I enjoyed a bigger sound, one that increased the size of the soundstage considerably. While the Trenner & Friedls don’t necessarily flesh out more detail than the Ravens, they do excel preternaturally at capturing decay. This makes the Osiris an ideal partner while listening to most of my 2L Recordings CDs, which are usually recorded in big, spacious Norwegian churches.

With Tomba Sonora, a recording that captures five voices and four cellos inside an old mausoleum, I had noted with the Raven IIs that it was occasionally tricky to tell where the voices ended and the cellos began—something that is intentional in a recording designed to examine how these sounds blend as they bounce around the room. With the Osiris mated to the Linear Tube Audio separates, I could hear just a little deeper into the recording to the point where I could follow the direction in which the reflections were traveling, and the cellos were more easy to identify.

That might not be the fairest comparison, since the Osiris are much more expensive than the Raven IIs, and I found myself wondering, once again, how the big Ravens with the LTA amps would address these complexities. Perhaps that’s not the point at all. The beauty with this match merely showed how the ZOTL40 and the microZOTLs are far more flexible when it comes to speaker choices than the Z10.


Ultimately, that doesn’t matter. I said in my review of both the Z10 and the Ravens that I would gladly buy both and live happily ever after. I feel no differently about the Raven IIs and the Linear Tube Audio separates. If you’re considering owning either brand, you should investigate them together. Christopher Hildebrand would surely assist you in his gorgeous new space at the Fern & Roby headquarters.

Also, I’ve heard the Z10 with Spatial Audio loudspeakers at several high-end audio shows over the last year, and that’s an amazing and compelling choice as well. But I’ve also noticed the Linear Tube Audio ZOTL40 and microZOTL in many other rooms with all kinds of room partners, and the result is always typical LTA—exceptionally clean and clear and gorgeous.

My time with the Linear Tube Audio ZOTL40 Reference power amplifier and microZOTL Reference preamplifier has only prompted me to consider all of the possible combinations with Fern & Roby speakers, and others as well. That choice has also become more complicated with the introduction of the new $7650 Z40 integrated amplifier, which uses the ZOTL40 design with LTA’s digital control system. Could that be the LTA amp that decides everything for me? Time will only tell, and I continue to believe that this is the most interesting amplifier manufacturer to appear in a very long time.