Linear Tube Audio ZOTL40 Mk.II power amplifier Page 2

"Truth of timbre is the mother's milk of perfectionist audio," Bill Brier used to say. It's a simple fact: the more any hi-fi system makes instruments and voices sound like themselves, the more diverse recordings it will enjoyably reproduce. By that important measure, the Zu speakers are marvels of sonic lactation. The Woo WA5 delivered a full spectrum of saturated natural tones with the Soul Supremes. The ZOTL40 did not.

Driving DeVore Fidelity Orangutan O/93s
My first impressions of the ZOTL40 Mk.II driving DeVore's two-way Orangutan O/93 speakers ($8400/pair) was of tight regulation, and a sense of music being slightly too damped. With a promo pressing of Karl Richter conducting vocal soloists and the Munich Bach Chorus and Orchestra in choruses and arias from J.S. Bach's St. Matthew Passion (mono "tulips" LP, Deutsche Grammophon LPEM 19 233), the imaging and clarity created the impression of low-distortion playback. But the music felt inexplicably and distractingly stiff, the Munich Choirboys bloodless.

Hoping for better results, I switched preamps: from the Pass Labs HPA-1 to Linear Tube Audio's own microZOTL2.0. (Note: I am the microZOTL2.0's biggest fan. It costs $1235, and drives both headphones and power amplifiers as if it should cost several times as much.)


Tone color and liquidity improved with the synergy between these two LTA products. With this LTA pairing I used AMG's Giro G9 turntable and 9W2 tonearm ($10,000, see "Gramophone Dreams" elsewhere in this issue), and EMT's ISD 75 moving-coil cartridge ($1700). The digital source was my trusty Integra DPS-7.2 DVD player ($799.99 when new in 2001), used as a CD transport with Mytek HiFi's Manhattan II DAC ($5995).

Driving the DeVore Orangutan O/93s, the two ZOTLs sounded ever so slightly wet, moderately colorful, dynamic, and elegantly detailed.

Driving Maggies & Quads
As always, the Magnepan .7 ($1400/pair) is my acid test for an amplifier's delivery of current into low impedances—in this case, 2 ohms. To my surprise, the ZOTL40 Mk.II propelled the Maggies' 57" panels with a firm, steady hand. Ito Ema's Steinway didn't sound as big or as weighty or as hyperdetailed through ZOTL40 as through the Bel Canto REF600Ms, but the LTA held its own, sounding clean, smooth, and easy as it produced an engaging facsimile of Ema playing J.S. Bach's Goldberg Variations (CD, M•A Recordings M024A). The ZOTL40 reproduced her touch on both halves of the keyboard with equal weight and virtuosity.

Remarkably, the ZOTL40 Mk.II sounded more sweet and feminine driving the Maggies' less sensitive (86dB/2.83V/m at 500Hz), low-impedance load than it did with the easy-to-drive Zu, Falcon, and DeVore speakers. Perhaps this newfound sweetness was caused by a shift in damping factor?

I thought the ZOTL40 Mk.II might make a good partner for Quad's venerable, original ESL speaker (nicknamed the "ESL-57," for the year of its debut), so I took it to a friend's house and installed it between his expensive MSB DAC and restored ESLs. I was surprised. Unlike 98% of the amps I've tried with this beloved but demanding electrostatic speaker—I've owned four pairs—the ZOTL40 Mk.II did not crap out. It actually drove the ESLs pretty well, sounding attractive and easy on the ears, if a bit flat and boring.

Enter Mr. O
First Watt's J2 ($4000), a 25Wpc amplifier designed by Nelson Pass, won't drive the Quad ESLs (I tried it), but the J2 is very difficult to beat when used with sensitive speakers of impedances of 6 ohms or more.

So I wasn't surprised when, into the 10-ohm Orangutan O/93s, the ZOTL40 Mk.II sounded less true of tone than the First Watt, with weaker midrange presence and less palpability of high-frequency detail. The ZOTL40 had slightly tighter bass, but bass sounds were less colorful than the J2's—and less so than real life. The ZOTL40's soundstage felt artificially vacuous. The J2's soundstage was fully oxygenated. Both amplifiers drew very detailed images.


My objectivist friend, Mr. O., sat next to me on the couch as I began comparing the 40Wpc, 9.7lb, $5800 ZOTL40 Mk.II to the 35Wpc, 46.3lb, $2195 PrimaLuna ProLogue Premium. Both amps are all-tube, the PrimaLuna using EL34 output tubes, the ZOTL40 the KT77 equivalents.

For this comparison I used the DeVore Fidelity Orangutan O/93 loudspeakers and, with each power amp, a preamp made by the same company: LTA's microZOTL2.0 ($1100) with the ZOTL40, and PrimaLuna's ProLogue Premium ($2195) with, well, PrimaLuna's ProLogue Premium.

Right away, O. preferred the Linear Tube Audio system. And when I played Ito Ema's Goldberg Variations, he got very enthused. "The LTA gear washes all that fuzzy tube distortion right out of the picture! The ZOTLs make the PrimaLunas sound bloated!"

It was obvious: The ZOTLs played Ema's Bach with more detail, transparency, and force than did the ProLogue Premiums, and the LTAs' bass was tighter. But! the PrimaLunas' superior image density and more realistic tone made the LTAs sound starved and skeletal.

"The ZOTL amp has definition!"

So what? I felt that the PrimaLuna amplification got closer to the sounds of real people playing real musical instruments in real spaces.

You know how a piano sounds when the pianist uses the right pedal? How each note expands, develops its harmonics, then reverberates outward into space? How it combines and mutates with notes played before and/or after it? How so much of Bach's cosmic poetry is created simply by letting his notes hang in air? Unfortunately, those sorts of beauty were missing from the sound of the Linear Tube Audio system. So were Ito Ema's pregnant pauses and enticingly eccentric phrasings, and her Steinway's weight and body. But when the PrimaLunas drove those same DeVore Orangutan O/93s, it all came back.

Recognizing the truth of this, Mr. Objectivity conceded that the LTA gear was losing a noticeable amount of legitimate low-level information.

"Neither amplifier is right!" O. opined.

Sitting silently, we played Brigitte Fontaine's Comme à la Radio (LP, Superior Viaduct SV042) all the way through, twice: first through the PrimaLuna system, then with the Linear Tube Audio components. This 1970 studio recording has more than a dollop of added reverb. Through the PrimaLunas, the voices of Fontaine and her collaborator, Areski Belkacem, floated richly over the reverberant drone of sitar and staccato bongos. The PrimaLuna ProLogue Premium components showed me this artificial space, as well as the audio manipulations that generated it. The ZOTLs reduced the scale and presence of these vibrating illusions to unnoticeability, and Fontaine's voice sounded dry and disembodied.

O. started talking—shouting. "They're both wrong! The real truth is somewhere in between!"

"But O.! There are no truths in audio—at least, not whole truths or real truths. There are only components that sound ridiculously different from each other, each showing off its own personal bits of truth."

Audio connoisseurship is the art and practice of deciding which bits of truth suit our personal taste. I preferred the PrimaLunas' more feminine truths of accurate tone and substantial body. Mr. O. preferred Linear Tube Audio's more masculine truths of realistic impact and fine detail. My old friend Bill Brier would have preferred neither. He believed that a good hi-fi should deliver realistic impact and accurate tone.

Because of my never-ending love for Linear Tube Audio's microZOTL2.0, I had extremely high expectations for the ZOTL40 Mk.II power amplifier. I imagined that these two David Berning designs would combine perfectly, creating an enjoyably balanced, powerfully spoken tube amplification system at a reasonable price. But after much listening, comparing, and deliberating, I concluded that while the microZOTL40 Mk.II is a strong, remarkably clean-sounding 40Wpc amplifier that could drive a wide range of speaker loads, it makes only modest magic at a somewhat immodest price.

Linear Tube Audio
Washington, DC
(301) 448-1534

tonykaz's picture

I'm feeling that I now have to lower my expectations on tube gear reviews, for darn good reasons:

A piece of tube gear is like a Turntable/Arm with it's tubes being a (phono cartridge type) variable.

The Pro Audio guys I know will pull their hair out looking for "Good Sounding Tubes", say'n stuff like that tube "sounds like shit!!!"

My old supplier, Art Ferris of Audible Illusions, carefully selected the tubes in all the Modulus 2 preamps he built and sold. He said it was his secret sauce.

Today our very own Kevin Deal has become the KING of tubes by being a reliable supplier of quality sounding glass. His importing PrimaLuna and Mystere speaks to his mastery along with Schiit owners that I know buying glass from Upscale.

My own Conrad-Johnson MV-45a's performance was from superb tubes.

Willian Z.Johnson would send Audio Research gear to Harry Pierson at TAS, those pieces contained very special glass.

The last headphone Meet I went to probably had 50 headphone amps active, the group of headphone tryers ( including me ) gravitated to a Schiit Valhalla 2 Amp who's owner loaded the darn thing with Russian Glass, it was easily the best sounding Amp at the Meet. Jude Mansilla's Schiit Rag/Yggy was there but sounded flat by comparison ( breaking my personal Yggy bubble, oh well ).

During my Retail days, I sold Solid State electronics for it's consistent performance. I also had the complete lines of Conrad-Johnson & Audible Illusions Pre-amps which didn't quite sell well compared to my Electrocompaniet & PS Audio Sales. Now, I realize that I wasn't focusing on careful Tube Selection. I was focusing on Phono Cartridges and Turntables, our specialties !

Tube guys are West Coast, I think.

UpScale in LA
Bottle head up in Washington
All those Schiit Valhalla & Lyr tube rollers seem to be West Coasters.

But the Garage 1217 folks, the Feliks folks are internet and thus International. These are the most serious Tube Rollers on the Audiophile Planet.

I'm coming to think that a piece of Tube Gear with it's chassis, power supply, circuit board & wiring make up a Textured Canvas with the Tubes themselves being the Amplifier reviewed.

Tony in Michigan

John Atkinson's picture
tonykaz wrote:
A piece of tube gear is like a Turntable/Arm with it's tubes being a (phono cartridge type) variable.

I understand that in The Absolute Sound's review of this amplifier, the reviewer "rolled the tubes" until he ended up with something that he felt sounded better than those supplied. Our strict policy is to review tube gear with the tubes supplied and recommended by the manufacturer, because that is what our readers will be auditioning.

John Atkinson
Editor, Stereophile

tonykaz's picture

Of course, I understand your position.

My position ( and the position of any owner/purchaser ) is the variable nature of the specific glass tube doing the amplification work.

The mechanical stuff making up a Valve piece is the support architecture that enables the tubes to provide their magic.

A Tube Gear Review, therefore, seems to be a good piece of writing to accurately describe how this circuit & chassis design is likely to be useful for Valve Amplification in an audiophile's ( stereophile's ) home music system.

This type of writing is exactly the type that our Mr.Reichert is the Master of and why he is at the very top of the Audio Journalism pyramid... and probably why Stereophile feels lucky to have discovered him.

Glass Tubes are a variable... OK, we all can accept that fact, can't we?

Many of us seem to realize that when a Tube piece of gear is "on Song" it's darn near impossible for any Solid State piece of gear to sound anywhere near as good...

but, a superb design of Solid State gear, such as: a D'agostino , a Levison, an Electrocompaniet, a Pass and probably a good few more including my little Schiit Asgard 2 are consistantly satisfying and therefore well worth owning.

I contend that today's Stereophile readership are aware of Vacuum Tubes possibilities and therefore expect the reviewers to provide insight into how to make a reviewed piece of gear sing like Pavarotti.

In a great many ways, Stereophile has raised the bar.

It's time to take Tube Gear Reviews to the next level.

Betcha Kevin Deal is ready to help.

Tony in Michigan

ps. tubes ( themselves ) are cheap $, probably the cheapest upgrade anyone could make.

Birdstone's picture

you say your reviewrs only use the tubes supplied by the manufacturer but AD used upgraded tubes on the prima luna progue review. this is what he said .. "And then, when I replaced the Premium's stock, PrimaLuna-branded EL34 tubes with the Russian-made Tung-Sol KT120s sent to me, for trial, by PrimaLuna distributor Kevin Deal, I was even more impressed with those—an $80 option at time of purchase. I also preferred to use the KT120s in Triode mode." Kevin Deal was allowed to upgrade the tube to make his amp up to snuf. that Kevin gets away with murder.

John Atkinson's picture
Birdstone wrote:
you say your reviewers only use the tubes supplied by the manufacturer but AD used upgraded tubes on the prima luna prologue review.

Correct. And as you correctly quote Art as saying, the Russian-made Tung-Sol KT120s were supplied by the PrimaLuna distributor and are an $80 option at time of purchase.

John Atkinson
Editor, Stereophile

woodford's picture

it would be interesting to know *which* KT77s were in use. i recently replaced the GL KT88s in my amp with GL KT77s, and it sounds like a completely different amp.

Linear Tube Audio's picture

Current production Genalex Gold Lion KT77s were used. We've been considering a return to EL34 as the stock power tube, especially for efficient speakers. When we made the change to KT77s for the Mk.II version, the primary listening systems had speakers less efficient than any of those used in this review.

If anyone is headed to RMAF, you can role-play as Herb and Mr. O in front of the ZOTL40 and the Orangutans, as we'll have that pairing along with a Fern & Roby turntable and phono stage as a source.

mrkaic's picture

I am sure I speak for many when I ask -- what happened to Bill Brier?

Herb Reichert's picture

joined the navy became a radar tech rolled a Chevy V8-powered MGA got out of navy quick became an electronic engineer at HP and a major local drag racer -- lost track of him years ago

mrkaic's picture

What a great guy!

Anton's picture

Heck, I can't believe we didn't get 2500 words on power cord rolling!

I like reviews where, to steal an auto racing phrase, ya run what they brung.

Fine review, Herb!

tonykaz's picture

Now, I ask you, would you consider spending $6,000 for this little amp that doesn't seem to perform up to it's price class?

Geez, we're going up against one of Blackie's Stereo 70's, a $2,000 PrimaLuna, a $600 Fisher 500C from eBay, those new Schiit Amps for $600 each or even a Mint Krell KSA 100 used for $1,500.

For $6,000 Grand I'd be expecting Kevin Deal's better tubes and the ability to play Quad ESL 57s, wouldn't you?

Run what ya brung:

I'd presume that you'd first get your auto "tuned-up" nicely, enough air in the tires, ball joints adjusted, brakes not pulling or rubbing, low restriction air cleaner, slippery synthetic Oil, low rolling resistance tires, the entire chassis stripped out of weight and the best darn Sunoco 260 plus the Nitro bottle hidden under the front seat. ( if you could )

The Manufacturer's comments: the Print Edition mentions their pursuit of Clarity, Neutrality with Uncolored Detail. Mr.Schneider also suggests that this Amp seems to be a Polarizing product.

My contention:

If we're gonna give this little Amp ( a possible prickly performer ) made by one of our favorite Electronics Builders, a fair chance of a successful debut, we should at least get our Glass selected properly. The manufacturer isn't building confidence so it's pretty much up to the reviewer who accepted this challenge, isn't it?

I have to accept that all Tube Gear is Tube selection dependent, I'd like the reviewers to go the extra mile to present the possible range of performance a reviewed piece presents. Isn't that what reviewing tube gear is all about? Solid State is fixed, tube gear is variable. Review Loudspeakers with a few differing amps, try a range of phono cartridges with a Turntable/Arm review, have a closer look at all the variables.

Reviewing Tube Gear is hard work that can be well done, I hope that our better reviewers step up to it's challenges and excel.

Tony in Michigan

Herb Reichert's picture

spent a lot of time in the pits 'runnin' what we brung' at Union Grove dragstrip in Wisconsin

Ludcam's picture

Hi JA and HR. I was looking at this amp for my system and found this review helpful.

I'm glad that Herb feels comfortable identifying some tube gear as "sweet and feminine" sounding and that Stereophile doesn't edit this informative content. Moreover, I agree that it is hard to understand let alone measure how a piece of gear is "neutral" (right HR, what does that mean?) or "accurate" (I hate that word too). Those concepts lack specificity and are not related to sound reproducing equipment.

I've been anxious that my current system was sounding too "good-with-money and Jewish" so adding a little bit of that "sweet and feminine" sound would really help me get to the soul of the music. Sometimes, though, when I go to my friends house I like his more Black sounding system. So much PRAT! Get's me tapping my toes like Al Jolson.

Oh well, time to go beat my chest.