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They Are Back
Tenor Audio Makes a Comeback With Their New High-end, Hybrid 350M Monoblock Amplifiers
by Ernie Fisher

It was immediately after the Montreal Audio Show, back in April of 2008, that my friend and ex partner Sol Scharf volunteered to make use of his house as the auditioning studio for the totally re-designed Tenor Audio amps.

Having auditioned them under uncontrolled conditions at the show hinted at something very special. The first day with Kharma speakers, the Tenors sounded sublime, while the following day connected to Avalon speakers, I didn’t hear peak performance. Sol and I proposed an audition, using Sol’s source component, an Audio Aero Classic player (same as mine) and his loudspeakers, a pair of WLM Grand Violas, one of my all-time favourite pair of loudspeakers. Everything had been connected to the $10K RCM Bonasus integrated tube amp using Valhalla cables throughout. Enter the Tenors.

Creating art is one thing, but designing a work of art is a process of achieving the complex, abstract succession of ideas and inspirations and connecting them to the arts.

And the Tenor’s designers didn’t disappoint as they succeeded in creating the world’s best looking amplifiers with an equally stunning preamp design matching the amps’ appearance. The sculptured sigmoid front panels are made of cherry wood, hand polished to perfection. The centre window — a round back-lit design with the company logo shows when the amp is in the standby mode, glowing red, and in the operating mode when glowing blue — a touch of class and ever-so enticing. The main AC switch is located on each amp’s rear panel, while the standby and mute switches are placed in front under the faceplate. Also on the rear panel, two sets of speaker terminals, a pair of RCA inputs and a pair of XLR inputs are logically arranged.

Each monoblock measures 19.5 inches wide, 28 inches deep, 9.5 inches high and weighs 118 lbs (53.5 kg); the shipping weight in the custom road case is 148 lbs (67.2 kg).

Sol and I both agreed that the amps are beautiful and we hoped that their performance would match their appearance.

The Sound
After choosing some familiar recordings — an eclectic mix ranging from Beethoven to Miles — we began with our listening session. Beethoven’s Pastoral Symphony was up first and it took less than 10 seconds for us to know that we were listening to something exceptional, distinctive and awe-inspiring. Sol and I looked at one another with astonishment, as we didn’t expect an enormous improvement over Sol’s system, which was selected for its great synergistic performance and its musical potency. However, all-round musical improvements were not only extensive, but also illuminating as the amps clearly unfurled the most delicate harmonics of the music.

The first few minutes of listening had me scratching my head with incredulity for all that had changed in the system set-up was the replacement one amp with another. The only additional component in the system was the prototype Tenor preamplifier; (the finished version will be available in a few months and will also feature an elaborate phono stage).

Sol’s reaction was the same as mine and we began to discuss what we were hearing and how describe the sound; the discussion lasted for several hours.

Next day, early in the morning, I took my compilation CD and again fired up the Tenor system. In an effort to ascertain the amp’s performance characteristics and how close it is to the truth, the musical nucleus, I like to use musical program material that challenges audio systems. To establish the amplifiers’ ability to resolve bass fundamentals and harmonics, I used my compilation CD that begins with bass, three basses to be exact. This established the amplifiers skill to handle everything bass. The next tracks feature male vocals (a jazzy blues arrangement), Mancini’s theme from The Pink Panther, bluesy female vocals, Hammond B3s, of course, opera and classical music —altogether about 65 minutes of music. Well, I listened to it all once, then once again with Sol; then, with the help of Sol’s Magnum MD108 tuner, we both listened to Montreal’s CBC and jazz stations. Later that day, while Sol went about his business, I listened to some more tunes and tried to devise a formula that could define the sound of the amps. Having done this many times in the past, it should have been easy, but it wasn’t and after some serious thinking, I came to the conclusion that, while it is extremely difficult to properly describe sound, it is even more perplexing to explicate sound one has never heard before.

The Tenor amps are almost indefinable due to the fact that they do not manipulate, modify, add or subtract from the organic reality of music, its instruments and performers. The amplifiers do not have better resolution than some other high-end amps I have auditioned; nor do I hear better tonal equilibrium or imaging; bass, midrange and treble areas of the Tenor’s frequency reach are very refined, by any standards, but are in line with other great amps I know. The difference, however, is in the Tenors’ ability to evaporate into thin air, leaving nothing behind but music. It’s the kind of occurrence that lends credibility to the often-used term “transparency” — the see-through quality. And that’s precisely what you get when listening to the Tenors, though you can see them, they do not conceal or obscure the complexity of musical composition and the harmonic patterns of its instruments. All aforementioned sonic elements — resolution, balance, imaging, bass and treble — are joined uncannily and seem a little less confined than in any other amplifier I have auditioned. Though I know of some amps that sound similar (Wyetech Labs original Topaz and the new Ruby Series prototypes I have in-house now), the Tenors still manage to heighten the sonic refinement. Among the many delicate fine distinctions, I noticed that every note in any frequency segment has its own singular environment, but blends insidiously into euphonious melody.

Listening to the Tenor amps is experiencing the integral energy of the music, which allows an unblemished view into the sound-scape from a high observation point. For me, the amplifiers evoke the impression that everything audio is in good order.

Synopsis & Commentary
Well, I have no hesitation nominating the Tenor amplifiers the best of which I know. They delivered the best sound Sol and I have ever heard and taught a couple of well-seasoned audiophiles and music lovers what audio can be when design is approached like fine art.

I’m tempted to run a list of all the great amplifiers I have auditioned over the 22 years of evaluating audio components, if for no other reason than to show that they are around. My first audition of a Tenor amp — a 15 w/ch design — was about seven years ago. It counted among the top ranking designs; but then again, most serious high-end amps I know of have a number of sonic elements resembling those of the Tenors. Nevertheless, I have yet to hear one that will outperform the 350Ms’ all-round organic distinction. The Tenors’ musical quality is off the chart, the build quality is in line with German precision engineering with the attention to details of Swiss watchmakers; and the amps’ exterior design reminds me of the skills of Italian instrument makers. In other words, there isn’t anything unrefined.

It is important to choose loudspeakers that allow the amps to be heard without adding colouration. The Kharmas were a great match, though, I preferred the WLM Grand Violas for a more relaxed, more organic equivalent. However, I believe that any well-designed loudspeaker will sound good driven by the Tenor amplifiers. Needless to say, it is important to use the best back-up system components and to exercise suitable care when setting up. When all things are done correctly, you’ll end up with something very special, your very own audio art.


X1350M Monoblocks Tenor Audio

Tenor Audio Inc.
17 Willow Bay Drive
Midhurst, ON L0L 1X1

T. 705.790.6444



The amplifiers boast numerous, ingenious design features beginning with the power supply. It’s designed around a customized high-current transformer that handles different international voltages and frequencies, and provides seventeen specific line voltages for each stage of the amplification process.

Customers, who live outside North America, are asked to specify voltage and frequency so that Tenor can provide the necessary AC cords, amongst other things.

Amplification is achieved with a combination of vacuum tubes and transistors.

The first amplification stage is based on the original OTL (Output Transformer-Less)
concept pioneered by Tenor in the late 1990’s. This stage provides 100% of the voltage gain. A high voltage mini OTL powers two parallel banks of high-current MOSFETS. The devices which, when combined at the outputs, deliver over 350 watts into an 8 ohm load. Speaker terminal voltage remains practically unchanged from the vacuum tube stage in a unity gain configuration whereby the power differential beyond the first stage comes from the current delivered by the MOSFETS.

The design features a dual-core power transformer rated at 1,875 KVA (the older design used 1.5 KVA transformers). Tenor chose hand-selected input tubes — two Tungsol ECC8035, one ECC99 and six GE 7044.

The amplifiers boast a sophisticated protection circuit, which allows them to operate at peak potential while monitoring low AC main voltage, DC offset at speaker terminals, AC at speaker terminals, static discharge, ground pollution and RF (Radio Frequency) levels. In case of unstable conditions, the amplifier will automatically protect itself by “muting” (the front panel window will change from blue to red when this occurs), whereby the inputs are shorted through a resistor to the ground and bias is removed to the output transistors. This is achieved without interfering with the audio signal.

The specifications do not necessarily reveal what these amps can do, but they are well documented.
Voltage gains are 32dB unbalanced and 30dB balanced. Each amp is rated at 1400 watts, 700 watts and 350 watts into 2, 4 and 8 ohms respectively @ 1kHz, 120 VAC.

Signal to noise ratio (reference to 10 W) is -94 dBA; at rated output -115 dBA; frequency response is from 3Hz to 200k Hz (± 3dB); total harmonic distortion @ 5 W 20 to 20K is < 0.05%; @ 10 W < 0.04%; @ 350 W < 0.17%; intermodulation distortion @ 10W to 100W is < .01% to < 0.02%; maximum output current at 1kHz, 2 ohms is 80 amperes peak to peak (that’s a lot); input impedance @1kHz 20K ohms unbalanced, 33K ohms balanced; output impedance is 0.08 ohms; damping factor is 100; output DC offset is less than 1.0 mv DC; rise time is1.15 ms @ 10 KHz.

In pure Class A the amp delivers 13 watts; input sensitivity for 350 W, 8 ohms @ 1kHz is 1.3 V balanced and 1.5 V unbalanced with zero global negative feedback.

The build quality is second to none and seems a continuation of the amp’s exterior artwork.
Of course, such a powerful amplifier develops quite a bit of heat and Tenor dissipates it effectively with two banks of heat sinks and a clever, natural convection system.

To prevent vibrations and resonance from reaching critical components, Tenor suspended the audio board entirely. The amps are designed to “soft start” with a three-minute delay while the amp is warming up (see indicator lights). Two sets of WBT Signature Platinum binding posts allow bi-wiring with premium cables.

Be prepared to use a bit more AC power as each amp gobbles 1850 watts operating at full tilt and 280 watts while idle.

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