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Reviewer: Mike Malinowski
Source: Walker Black Diamond turntable; Walker Reference phono preamp; Clearaudio Goldfinger
Preamp: VTL TL-7.5 Reference
Amp: darTZeel NHB-108; VTL S400; Tenor 350MM [under review]
Speakers: Wilson X-2 Alexandria
Cables: Transparent Opus, Silent Source, Transparent XL w/MM interconnect to amp; Silent Source and Xtreme between phono pre and preamp
Stands: Michael Green racks, VPI phono stand, Zoethecus, Walker Prologue Amp Stand
Powerline conditioning: Furman Balanced Power, Walker Audio Velocitor S, PS Audio 300M
Sundry accessories: Walker Audio Valid Points resonance control discs; ASC tube traps; Echo Buster absorbent and diffuser panels; Argent Room Lens; separate 90-amp sub panel feeding five dedicated cryo'd outlets; Loricraft Model 4 record cleaner; Walker Talisman
Room size: 22' x 17' x 8' (double sheetrock on 2"x 6" framing in basement)
Review component retail: $90,000/pr Canadian

Introduction
My first contact with Tenor was in 2004. I was already the proud owner of the 75i OTL Tenor monoblocks - beautiful, transparent, with a wonderful 3D sound. Through the Internet and some knowledgeable insiders, I heard the buzz about a powerful new Tenor hybrid. After a brief listening at the New York HE Show, I left with slightly mixed feelings. I don't know whether it was the speaker, the source material or those bad hotel rooms yet I was looking for that live musical OTL immersion experience that frankly, the show room did not deliver. The Tenor 300M's room did not live up to the hype. But one of the things I've learned is not to draw conclusions based on show conditions. A great-sounding room probably is indicative of pretty good components. Yet the converse is not necessarily true. A bad room does not necessarily mean bad components. However, the Tenor 75is were too good and the promise of a hybrid too intriguing to not pursue this further. I sent several e-mails and a few phone calls to Tenor to discuss a potential review of their new 300M monoblocks. I received a call from François, managing director of Tenor Audio, thanking me for my interest. He discussed the amp and talked proudly of its design and his belief that they were the world's finest amplifiers. François then proceeded to tell me that unfortunately, Tenor Audio was closing doors and filing for bankruptcy.


It was a stark and stunning announcement. Tenor was François's dream and his baby. He, along with Robert Lamarre and Michel Vanden Broeck, had nurtured the company from concept to somewhat meteoric rise. To pick up the phone and call a reviewer with these news was certainly a painful experience he didn't have to do as the announcement would hit the streets shortly. François talked of his dream that one day a stronger Tenor would rise from bankruptcy and he promised that when it returned, he would contact me. In that short conversation, he came across as a man devastated by loss but seemingly with a foundation of honor and integrity. No doubt, it was the single worst day of his life.


Fast forward two years later with an e-mail from François announcing that Tenor was indeed reborn. "I spent the last two years reclaiming Tenor and developing an entirely new amplifier." He wished to discuss its world premiere review. It was a surprise to say the least. Ongoing discussions led to a Montreal meeting at their factory with the partners and head designer Michel Vanden Broeck, an exceptional opportunity to get a comprehensive understanding of the new Tenor Inc. Company.
I had both anticipation and uneasiness as the review approached. When a manufacturer unabashedly sets the bar at the very top, with prices to match, performance that is just "very good" or even slightly better than other great amps would be a failure in this context. So then, what are the expectations of a $90,000 pair of monoblocks? This also leads into another somewhat delicate situation. My job is to review components, not to analyze cash flow and balance sheets or to make a determination as to the viability of a company. However, in this case I think it's slightly more complex. Here we have a firm that burst onto the audio scene and in a relatively short period of time rose to the top, selling millions of dollars worth of products and then just as quickly fell into bankruptcy. Now reborn, the same company has launched a product priced at more than double its previous flagship model. What if the company still does not have the financial stability and management team in place to support this high-end product line for the long haul? Is that even a question for the review? Even if the amp were superior, could I in good conscience recommend a $90,000 amplifier if I had suspicions as to the company's stability and longevity? Then there were questions as to reliability. After all, the original 300Ms from the old company did have initial production problems.


I went in with plenty of questions. What I found at Tenor was amazing frankness and openness about their past. When discussing the company's history, François spoke candidly of both the success and failure of the original 300Ms. "Initially with the 300M's output transistor, the matching techniques were not nearly as sophisticated as today which affected some of the initial production units. However, that problem was solved quickly. The other problem was with four output tubes, the 6H30s. Although the problem did not appear during design and testing, some production tubes overheated, causing fuses and resistors to blow. We recalled every amp, paid shipping both ways and updated fuses and resistors. Now, if the customer wishes to upgrade, we use 6N6s with slightly different values in the board and there are absolutely no problems any longer. The problem was not specifically with the tube, it was a minor circuit problem causing it to overheat under some circumstances. Again, this applies to the original 300M, not the 350M, which is a totally new design."


During my visit to Tenor, we spent much of the time discussing quality, reliability, the management team and yes, even a little finance. François and his team were as open and forthright as any manufacturer I've ever dealt with, period. They did not put a glossy spin on their past or a pretence on their present operation. What I found was a well-financed organization with experienced management, passionate leadership and a brilliant technical designer.


As a companion piece, I will publish an industry feature article describing the history of the old Tenor along with a current factory tour and new Tenor discussion. Of course, in business there are no guarantees but François has put together a seasoned, professional management team that would be the envy of certain Fortune 500 organizations. The owners group is well funded, with superior expertise in engineering, production, finance and management. The new Tenor is the antithesis of the stereotypical small shoestring audiophile company. The structure and management of the company has been significantly upgraded over the original Tenor Company, which should be comforting to anyone about to lay down $90K for an amplifier. They have a rational business plan and apparently the means to carry it out.

In this review, I'm sure I'll hit all of the intricate sonic descriptors spiced with the appropriate audiophile buzzwords but what really is important is my attempt to convey what puts these babies in a class by themselves. Their design, construction and sonic characteristics position them not just incrementally higher but in many cases into a whole new realm. I'm not talking about the short-term excitement with a spotlighted brilliantly edged sound that perks up your ears for 10 minutes but provides little long-term listening satisfaction. No, we're talking about a visceral, dynamic presence that I've never heard from any electronic component - ever. It is by far the least electronic, least mechanical playback device in my listening experience.


As a reviewer, I walk a fine line between presenting too much technical detail and too little - two distinct camps, two philosophies. Since Tenor offered unprecedented open access, I am taking this opportunity to present that window of information to you. If your eyes become glassy at the mere thought of OTL gain stages or MOSFET biasing, then simply skip to the sound section. For others, I believe here is a rare insight into the brilliance and passion of this dedicated group.


Design
Physically, the amp is stunningly elegant with a high-gloss wood face panel finished with 10 coats of lacquer and merely the singular Tenor logo backlit in the center. No switches, knobs or displays anywhere. The entire sides are curved massive flowing heat sinks for the output MOSFETs. It's a striking and distinctive esthetic you're not going to mistake for any other brand. However, when I first saw them at their factory, the new 350Ms did remind me. What could it be? Wait a minute, I know! They are visually identical to the original 300M monoblocks from the old Tenor Company. Apparently Tenor experimented with other visual designs yet François ultimately returned to their classic look.


"We spent a lot of money on the redesign. We tried several different designs in order to get a better look and frankly spent a lot of money. But in the end, we came back to the original design. Everybody loved the original design so we simply improved the look with a deeper glossy finish."


Based on the exterior, one might conclude that the 350M is nothing more than an upgraded 300M. Is the 350M really a new 'clean sheet' design or was there a smattering of marketing hype mixed in? Maybe you think it is just a Mark II version as is the case with many other companies. Boy would you be wrong. While the 350M builds on the concepts of the original 300M, virtually every important element of the 350M is new and unique, a process that took two years and $1,000,000 in R&D. Yes, both amplifiers use tube gain stages combined with a solid-state output but that's where the similarity ends. Everything was redesigned - transformers, regulation, gain stages, protection systems and most importantly, a completely new MOSFET output stage.


No matter what Tenor claims, the physical similarities with the original 300Ms will invite comparison so let's examine some of the original designs. I asked François to contrast the two design philosophies. "Although the 350M is based on the principles of the 300M including the harmonic control, the circuitry is different. The original circuitry was like one half the circuitry of the 75i OTL. The OTL is symmetrical so we took one half, modified the circuits to properly satisfy the requirements of the output stage including a higher voltage. At that time, we chose a special type of transistor IGBT (Insulated Gate Bipolar Transistor), which is not currently manufactured."


The IGBT functioned somewhere between a bipolar transistor and a MOSFET. You can drive it easily like a MOSFET but it also has some of the problems of a bipolar, including secondary breakdown failure mode, which to my layman understanding is essentially a runaway heat failure. Voltage increases, causing higher current, which increases heat non-uniformly in part of the chip, which in turn causes even more current and more heat, resulting in failure.