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REVIEW: Linear Tube Audio ZOTL40 MK II Amplifier (Tube)

Model:	ZOTL40 MK II
Category:	Amplifier (Tube)
Suggested Retail Price:	$5,800
Description:	Tube amplifier
Manufacturer URL:	Linear Tube Audio
Model Picture:	View

Review by jsm71 on January 28, 2017 at 10:31:36 IP Address: 74.83.35.140

Add Your Review for the ZOTL40 MK II

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I thought someone should start product reviews for Linear Tube Audio since they have such great products. Mark Schneider founded Linear Tube Audio in 2015. His first offering was to replicate David Berning's wildly successful MicroZOTL headphone amplifier. He did this with David Berning's blessing and approval to use his ZOTL patent for transformerless tube amplification.

The ZOTL40 MK II amp ($5,800) is rated at 40 watts, but that is conservatively low. The amp comes shipped with 4 KT77s, 2 12AX7s, and 2 12AU7s, all premium new-production Genelex Gold Lion tubes. The tubes are auto-biased. No fussing there. It's casing is a very plain looking black box, with a volume control and power indicator light on the front. Its shape is deeper than wide and on the tall side, unlike almost every amp out there. It won't score any eye candy points at all, but the sound makes up for it. Oh, and the amp weighs only 9.7 pounds. The back has single ended only inputs and outputs and the IEC connector for the power cord. The IEC connector also houses the on/off button, arguably badly placed in the back. LTA uses great parts and the assembly and wiring is first class all the way.

Apparently the design that David Berning uses in his own stunning amplifiers is very difficult to build by hand and nobody prior to Mark has been approved worthy to "carry the torch" and share his patent. In short order since 2015 Mark has come out with a small number of products each using the ZOTL technology.

For those unfamiliar with what Berning has figured out almost 20 years ago and patented, his amplifiers use tubes but no output transformers. Unlike other OTL amplifiers, Berning's design is truly unique. Read the notes on the LTA web site for an explanation. The benefit of removing output transformers is supreme clarity and linearity. Typical OTL amps have many downsides which I won't attempt to explain. Again, read the LTA web site. I've seen and heard a number of OTL amps and yes, they sound wonderful, but they carry compromises. If they didn't, we would see many more such designs in the tube world. It's much easier and less costly to simply built tube amps with output transformers.

I had a very nice tube amp prior to purchasing the LTA ZOTL40 MK II. I won't name it but it was a hand built push pull transformer based 40 watt design. The unit was assembled without circuit boards and wired point to point. It was also recently awarded product of the year from an industry publication. I felt I had bought my last amp. It was/is still a wonderful amp in the realm of transformer based tube amps.

A friend of mine who uses the same JansZen hybrid speakers that I have actually stepped up to the plate first with this amp and all but insisted I make the switch as well. I did, and he was right on with his recommendation. I didn't realize the effect output transformers had on the sound until they weren't there. The ZOTL design allows the beauty of tube sound to come through with no restrictions.

The ZOTL40 brings marked benefits to the sound and other benefits unrelated to the sound. First the sound benefits. Without transformers the output curve has the same linear flat line one would expect from solid state done right. Frequency response is flat from 8 hz to almost 50K hz. This range is noticable right out of the box. Bass extension and weight is superb, much better than my prior amp. Upper frequencies, where a lot of the soundstage is formed, is spectacular. This amp does the 3D thing better than any amp I've owned, solid state or tube. The amp is dead quiet as well. No transformer hum because, hey no transformers! Warm up time for a listening session is minutes, rather than the hour my last tube amp required. It has the best of tube sound and strength of solid state without any harshness at all. I would be remiss if I didn't mention how special this amp mates with speakers. Again, this is explained on the web site, but hearing has me believing this. My JansZen ESLs are very revealing and they have never sounded better. There are other amps that sound this good, but I'm talking about the monster $$$ amps we've all seen at audio shows. My prior amp was only $100 less expensive and I've sold it already. The sound improvements were not subtle.

As to other non-sound related benefits, these would include: tubes that are projected to last 10-20 years due to how easy they are driven, less generated heat, and the amazing 9.7 lb. weight of the amp.

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Product Weakness:	Industrial look and feel, power switch should be on the front.
Product Strengths:	Amazing sound value for the price, long tube life, featherweight product

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Associated Equipment for this Review:

Amplifier:	Linear Tube Audio ZOTL40 MK II
Preamplifier (or None if Integrated):	Cary SLP 98P
Sources (CDP/Turntable):	Marantz TT 15S1 turntable Lyra Delos with Bob's devices Sky 20, Marantz SA8004 SACD/CD
Speakers:	JansZen passive Valentina
Cables/Interconnects:	Cerious Technologies Graphine Extremes and Morrow level 4
Music Used (Genre/Selections):	all types
Type of Audition/Review:	Product Owner

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