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Positive Feedback ISSUE 75
Tenor Audio - The Line1
Linestage
Preamplifier/Headphone Amplifier
Tenor Audio, a tiny Canadian manufacturer that has merely a few products in its lineup, is best known for its hybrid amplifiers with a solid state output stage that works as a buffer instead of amplifying the signal (a unity gain configuration) and a tube-based gain stage. However, Tenor's history began with completely different products: OTL tube amps. As François Lemay, head of sales, recounts in his interview with Mike Malinowski, it all began very innocently, with a meeting with Robert Lamarre in 1998 during an audio show in Montreal where Lamarre was selling his speakers (see the whole interview HERE).. Six months later it turned out he only lived a few blocks away from Lemay—a fortunate coincidence. At the next occasion Lemay showed his newly-made friend an OTL-type amplifier, which was quite a discovery to Robert who had been strictly a SET guy up to that point. François Lemay knew the right people, including Michel Van den Broeck who had performed a few updates in his amplifier. Lemay suggested to Lamarre that they should hire Michel and have him design and build a 15-watt OTL monoblock amplifier. And that's how Tenor Company was started. They did their first show in 1998, with a static display of the new 15-watt OTL designed by Michel, because the unit was not yet finished. The working prototype was shown in 1999 and 2000. In the same year, Ultimate Audio magazine reviewed the amp in what turned out to be their last issue. Lemay says that it was 2000 that was really the beginning of Tenor operation. That's when they hired a cabinetmaker and Michel was designing and producing their first OTL amps. A year later, the company proudly introduced the OTL75 amp at the CES. Their first hybrid amp was designed in a record time of nine months – to put it in perspective, it took over three years to design their first OTL prototype. They planned to showcase it at the CES in 2003. Unfortunately, one of the amps along with an OTL was stolen. François still doesn't know how they managed to get $500,000 worth of orders on the amps although no one had yet heard the hybrid. The only problem at that point was to keep up with all the orders. They did the best they could to catch up on production, but at the same time the money was not pouring in as quickly. Around that time they introduced the amps at $28,000 retail. The problem was that they were selling them below actual production costs, which was a mistake. The second problem was that the US dollar began to drop, and the price list of the Canadian company was in United States dollars. It did help somewhat that Canada has a law that rebates some of the R&D costs back to the manufacturer. Since Tenor had huge R&D costs at the beginning, this rebate was essential for the company's cash flow. In 2003, due to a minor technical glitch in the process the government failed to refund their R&D money. The same problem recurred in 2004 and, what's worse, the company weren't even get an answer or explanation why the rebate was refused. And we're talking about $340,000 by that time. Although there were lots of orders pouring in, the start-up debt combined with the government's failure to refund the money resulted in a very difficult cash flow position. Together with a few other minor unfortunate events, it forced the company to declare bankruptcy in December 2004. Up to that time Tenor had manufactured 85 pairs of OTL monoblocks, 26 pairs of the 300 amplifiers and 18 of the 150s. The company's papers were extremely well-organized, every single penny was accounted for and nothing had been hidden—the bankruptcy receiver said never to have seen such an honesty in his life. The same day they went to their creditor bankruptcy meeting, François and Robert met Martin Labrecque who was interested in amplifiers. One thing led to another and the gentlemen came to the conclusion that with a product this good and with such a great designer like Michel Vanden Broeck, the company should continue. With the help of Martin, along with three other new investors: Jim Fairhead, Tom Moynihan and Jacques Pilon, they were able to buy back the Tenor assets. That's how a second stage in the company's life began, under the name Tenor Audio. Jim Fairhead became the company's president. Developing a new business plan as well as new research and development took two years. The new owners were able to give Michel additional equipment and funding to complete his research and to hire Jean-Pierre in 2005. The next year saw a new generation of Tenor Audio components, including the 350M monoblocks and the 175S stereo amplifier, although the commercial version of the former wasn't presented until 2007, when they were showcased at the Rocky Mountain Audiofest in Denver. The stereo amplifier that we have reviewed was displayed a year later, at the CES 2008 in Las Vegas. The preamplifier had to wait for its premiere another few years.
The Line1/Power1 was designed from the start as a reference product. And it has a corresponding price tag—it's one of the most expensive line stage preamplifiers on the market. The twin-chassis design concept is used to separate gain circuitry and power supply. The whole preamplifier is big, heavy and powerful. Its aluminium chassis and wooden elements both play an equally important role. The electronic circuit is based on General Electric NOS 6463 double triodes. A look at the preamp's rear panel reveals another thing: a headphone jack from Neutrik, with a clasp. We'll come back to this in the audition section. The 6463 tube had been designed to work as a computer switch, so it can be expected to offer good performance characteristics, reliability and long-term stability. However, the original technical documentation provided by Philips states that the tubes shouldn't be used in circuits susceptible to microphony, hum and noise. Michel Vanden Broeck has treated this warning very seriously and used a few design ideas as a preventive measure.
Vibration control includes multiple stages of decoupling via wood and rubber, internal board mountings, suspensions and dampening material. The main audio board suspension is designed for a resonant frequency of 20 Hz to isolate floor borne bass vibration and microphony effects. The chassis is very rigid, and the presence of wood helps to absorb vibration. There are special accordion-like rings placed on the tubes to protect from RF and EMI radiation, as well as help reduce vibration. Hum and noise has been minimized by moving the power supply to its own enclosure, separating the power supplies for the left and right channel, as well as using five separate power supplies per channel. Plate voltage is rectified in ultra-fast F.R.E.D diodes and filtered in a 4th order filter with two inductors and two banks of capacitors. Although the Tenor's heart operates on tubes, a 19th century technology, its microprocessor control is straight from the end of the 20th century. The microprocessor, which allows the user to change many settings in the menu, can be updated—there's a USB port available on the board. The preamplifier is operated with a neat remote control. Tenor Audio featured previously in High Fidelity • REVIEW: Tenor Audio 175S – power amplifier, see HERE SOUND Albums auditioned during this review • Le Jeu des pèlerins d'Emmaüs, Ensemble Organum, Marcel Pérès, "Musique D'Abord", Harmonia Mundi HMA1951347, CD (1990/2014). • 2 Plus 1, Greatest Hits Vol. 2, Sonic Son 115, CD (1997). • Alan Parsons Project, I Robot, Arista/Sony Music Japan SICP 30168, 2 x BSCD2 CD (1977/2013). • Billie Holiday, Billie Holiday, Clef/UMG Recordings UCCV-9470, "David Stone Martin 10 inch Collector's Selection", CD (1954/2013). • Charlie Parker & Dizzy Gillespie,Bird & Diz, Mercury/UMG Recordings UCCV-9466, „David Stone Martin 10 inch Collector's Selection", CD (1952/2013). • Czesław Niemen, Spodchmurykapelusza, Pomaton/EMI PTROMO CD 435, SP CD (2001). • David Gilmour, On An Island, EMI Records 3556952, CCD (2006). • Diary of Dreams, The Anatomy of Silence, Accession Records, A 132, CD (2012), reviewed HERE. • Electronic, Electronic, Factory Records/EMI Records 5099990743122, "2 CD Special Edition", 2 x CD (1991/2013). • John Coltrane, Expression, Impulse!/MCA Victor MVCZ-39, "Master of Jazz", K2 CD (1967/1996). • Nina Simone, Silk & Soul, RCA/BMG UK & Ireland 2876596202, CD (1967/2004). • Pery Como, Como Sings, RCA/BMG Japan BVCJ-37258, "RCA. 100 Years of Music", K2 CD (1959/2002). • Sohn, Tremors, 4AD/Hostess CAD3403CDJ, CD (2014). • The Allegri String Quartet, Shubert, Haydn, Ravel, Naim naimcd012, CD (?). • The Cure, Disintegration, Fiction Records 8393532, CD (1989). • The Pat Moran Quartet, While at Birdland, Bethlehem Records/Victor Entertainment VICJ-61470, "Bethlehem K2HD Mastering Series, No. 20", K2HD, CD (1957/2007). • Yello, Touch, Polydor 27194851, FLAC 16/44,1 (2009). I come back to this like a drunk to a bar, but I just can't help myself: the audition of the TechDAS Air Force One turntable, and particularly the way it played the album Teatr na drodze ("Theatre on the road") by the Polish band 2 Plus 1, was nothing short of a revelation for me (see HERE). I thought I knew how an audio system should sound like, as I had heard more outstanding systems than I could remember, but what I heard at home on that day was like an epiphany. I had no idea that the album recorded by the Polish band in 1978 sounded so damn good - mea culpa. My thinking had been based on many years of passionate listening to the band's subsequent album, Video, released in 1985. I bought it in a tiny bookstore in Bobowa, where I lived at that time, and since then I've listened to it hundreds of times. I got used to its problems, and I loved everything that was good about this music and sound.
But if we take analog album releases as a reference point, digital releases of 2 Plus 1 (alternatively 2+1 and Dwa Plus Jeden—the band used several types of spelling) are junk. In fact, the only CD release that I can recommend with good conscience is a reissue of a concept album with music dedicated to Zygmunt Cybulski, a well-known Polish actor who died tragically in 1967, titled Aktor (1977). In addition to the original material, the reissue also features a song recorded and sung by Justyna Steczkowska (see HERE). The album has been remastered by Mrs. Anna Wojtych who worked for some time as a sound and mastering engineer for DUX (by the way, this Polish label regularly advertises in a major British magazine dedicated to classical music, "BBC Music"). I was able to talk to her about her approach to remastering; our conversation can be found HERE. What I'm getting at is that digital album releases from this group (only two original albums and countless compilations) sound dynamically flat, are devoid of color and dynamics. However, if we play any of the compilations, for example Greatest Hits Vol. 2 digitally remastered by Sonic, on good audio equipment, the magic returns. It's still only an approximation of the quality offered by vinyl originals, but it is acceptable. On the best systems, or those whose sound is shaped in the right way, it sounds very, very good indeed. And even if in the back of my head I still keep what I once heard from Mr. Hideaki Nishikawa's turntable, playing it back on a quality audio equipment gives no less fun. The biggest problem of this type of reissues is a "thin" tonal quality. It seems that the material lacks saturation and harmonics, and what's left is just the basic tone. This often leads to brightness and one-dimensional, lifeless presentation. On the other hand, if a system or one of its components is characterized by the exact opposite set of characteristics, we receive an added value, as I've said before. An example of such a component is the Tenor Audio Line1/Power1 preamplifier. The primary role of the preamplifier in the audio path is that of volume control. All other functions, like input switching, DAC, signal buffering or amplification, are secondary. Hence, the simplest possible preamplifier can be reduced to an ordinary potentiometer, and this type of device bears a misleading name: "passive preamp." Sonically, it is very characteristic: ultra-precise definition and envelope, and no added coloration. Nearly all such preamps, including those using attenuator transformers, usually sound just like the digital 2 Plus 1 releases I've mentioned above. Not all of them, but some 99.99%. The Canadian preamplifier is on the other side of the rainbow. I have very rarely come across an audio component of such an intense, so clearly defined sound - clearly in the direction of body and mass. The preamp creates the kind of tonal quality the audiophiles dream about at night, never heard by sound engineers in good recording studies, unless it was while listening to live music. This is a powerful presentation with a clearly favored, fairly broad bass range. We get a sound that defies interpretation or assessment. Not because it is not impossible to do it, as it's actually quite easy, but because there is no such need. If that's what we are looking for, it will be our kind of sound for life. It is completely satisfactory, because the unit disappears from the equation, leaving us alone with the music. In its own interpretation, of course; that much should already be pretty clear. The music is good and velvety, with a powerful foundation at the bottom end. We don't pay attention to individual instruments, but rather to the way they correlate with the others. Vocals suddenly appear in front of us, and if it weren't for the fact that they are soon followed by an extremely well differentiated, powerful bass, we would have been left dumbfounded. Resolution, just like selectivity, does not seem too high. While this is true in the case of selectivity, as the preamplifier relies on tonal differentiation rather than on "drawing" phantom images, it is not so about resolution. The latter can be characterized as the amount of information we get. Not the amount of "detail"; this is different than detailness. Resolution means density and naturalness, warmth and "flow". The Tenor has plenty of it all. Its presentation is focused on the "here and now." Reverb and room acoustics, including that added in the studio, are in the shadow of the main sounds. It seems that the vocals and instruments are transferred to us, to our room. This happens in a very cultured manner, without attacking us with a close sound or popping-up before the speaker line. Actually, this line is only symbolic and there is no feeling that the sound is closed in any particular body or shape. Thanks to an active bass, especially the midbass, the presentation has a hell of momentum. The volume of sound is large, helped by a strong lower midrange.
The tonal quality is based on those two components, with the addition of a slightly rounded attack transient. The latter is so delicate that it does not feel as a lower dynamics. Yes, the sound is calm, but this is a result of internal warmth and overall "concord." It is beneficial to albums that often sound too flat, like The Alan Parsons Project I Robot, or David Gilmour's On An Island. The latter was recorded with the help of Polish musicians: Zbigniew Preissner wrote the orchestration and Leszek Możdżer played the piano on two tracks. The orchestra was conducted by Robert Ziegler, a conductor born in the United States and living in the UK, who collaborated on a joint project with Krzysztof Penderecki and Radiohead guitarist, Jonny Greenwood. This album was released by EMI in 2006, the final year when the record label still used copy-protection. Hence, it is a Copy Control Disc rather than Compact Disc and that is unfortunately audible. That's why the vinyl sounds so much better. Still, it sounded remarkable with the Tenor in the audio path. Dense guitars and a huge space, in which ship's siren decayed long and dark, as in the fog. HEADPHONES To treat the Tenor as a line stage preamplifier is normal and understandable, since that's its main task. Moving the headphone jack to the rear panel only seems to confirm that. This time, however, the decision was based something else. I assume it was an aesthetic consideration.
Listening to the Tenor working as a headphone amplifier it is hard not to get the impression that someone did a great job on it and that it is not just an additional feature but its integral component. It was not difficult to find out that Tenor's sonic character is simply amazing on headphones. A strong bass, emphasized lower midrange and delicate treble, combined with excellent resolution provide lots of fun with selecting the headphones and then listening to the music. Headphone amplifiers usually work best with particular headphones, and can sound poor with others. Top headphone amps, such as my reference Bakoon Product International HPA-21, allow any attached headphones to speak with their own voice. The Tenor Audio does the same. The Ultrasone Edition 5, the most expensive headphones I own at the moment (almost $5,000), sounded open and incredibly spacious, with a very good bass. The emphasized part of the midrange that is responsible for the spatial aspect did not dominate the presentation, but it was palpable. Precision, resolution and the quality of treble, however, were unbeatable; better than from the Ultrasone paired with the Bakoon. The sound was tighter, more accurate and closer with the HiFiMAN HE-6. Bass was better focused and the midrange emphasis completely disappeared. But the sound was inside the head and didn't have such good decay. It seems to me, however, that the performance created by the Sennheiser HD800 with Forza Audio Works cables deserves the highest recognition. Although neither as precise nor as tight or spacious as the two previous headphone designs, it was the Sennheisers that showed the most diverse sound tonally-wise, with the prettiest characteristics. With the Line1 we also get a reference headphone amplifier, and we won't need any other. The only remark that I have concerns voltage gain. To really get the HE-6 going you need to set the gain to "High" and, preferably, switch off all other outputs, except for the headphone output (in the menu). It turns out that other headphones, including those less demanding, also behave better in this mode. In systems such as mine, where the preamp worked best when set to "Low", starting a headphone listening session will require changing the settings. Conclusion There is no hiding the fact that the Canadian preamplifier modifies the signal. It would be even more difficult to hide the truth that all audio products do exactly the same. What's really matters then is how they do it. The Line1/Power1 makes for an easier listening. It will make each record sound at least interesting, of course as long as the music is interesting. The unit offers an exceptionally well-differentiated tonal quality. Hence, it does not replace every album with one and same disc, nor does it make recordings sound similar to each other. While the bass is strong and we will often hear it where we don't expect it, it is very well differentiated, both in terms of pace and color. The top end is rather sweet and recessed. The Takumi K-15 from Robert Koda, reviewed some time ago, is quite different in this respect (see HERE). A similar sounding treble is offered by the Soulution 720 preamplifier. The Ayon Audio Polaris II and Spheris II would be somewhere in the middle. Audio Research preamps sound similar, except that the Tenor does everything better and is more dynamic and colorful. It has its own distinct character. It makes recordings sound interesting, not tiresome. At the same time, it doesn't break them down to their constituent parts. The unit sums up what it receives from the source rather than analyzes it. It is a top high-end with a human face, without pretending that "neutrality" is possible in audio. The message it sends is clear and easy to read: the world is beautiful! DESIGN There is one main reason behind two-piece audio components, whether digital players, preamplifiers or power amplifiers: to separate sensitive audio amplification circuits from the power supply. This is done, for example, by Ayon Audio, Ancient Audio, Audio Research and others. The American VTL goes even further, additionally moving a microprocessor to its own separate enclosure. Tenor Audio uses the classic division: one enclosure houses amplification circuits and the other one is a power supply unit. The Line1/Power1 is a tube-based line stage preamplifier and headphone amplifier in one. It is very big, heavy and looks like a solid power amplifier. Its enclosure design is characteristic for this manufacturer. A rigid enclosure is built by bolting together thick anodized aluminum and wooden parts. Front panels are made of thick, beautifully finished solid wood.
The front panel of the amplification module sports a blue VFD display in the center. It shows the volume, currently selected input and output. The unit has a fairly extended menu where you can change all the settings. This is also where you can select the voltage gain: 14 or 21 dB. The display has a rather low contrast. Under the display there are four small buttons, the same as in the remote control unit, which is also largely made of wood. More important, however, seem to be two large knobs on the sides, also acting as buttons. They can be used to change the volume and select inputs, but also to move around the menu. The front panel of the power supply unit also sports a window in the center, but only with LEDs. They indicate power-on (red), plate and filament voltage (blue) and control (green).
The two modules are linked with two multi-core umbilical cords, terminated with extremely solid Amphenol plugs with gold-plated pins. Each channel has its own cord.
The amplification circuit is tube-based, with four General Electric 6463 (CV5304) dual triodes per channel. Originally designed for use in computer systems, they sport accordion-like heat sinks with rings made of carbon fiber and mica for additional vibration damping. At the input you can see huge, really massive polypropylene MKP capacitors from Epcos. These capacitors can be seen in other places, too, for example in cathode bias circuits. The main audio board is decoupled with soft rubber suspension grommets. This is one of many steps used for vibration control.
The output circuits seem to be housed on separate boards, mounted to the sides. You can see large shielded transformers, which seems to be output coupling transformers. Input connectors are soldered to a board mounted to the rear panel. Input switching is via relay switches. The whole interior looks great, but the attenuator is a real treat to the eye. It is a huge motorized potentiometer with a microprocessor-controlled stepper motor, mounted vertically on an isolated board away from the main circuit. I saw a similar potentiometer used in the best preamplifier I've heard so far, the Octave Jubilee Pre. The Octave potentiometer was not motorized, though. The entire Line1 remote control circuit was built by Tenor in-house. The same board also sports more coupling transformers—could inputs also be coupled in this way? The majority of internal wiring uses silver-plated copper wire in Teflon insulation, terminated with ultra-precise connectors used in microwave applications. You need to be careful when moving the power supply unit as its center of gravity is near the front panel. The reason for that is that this is where four EI type 100 W power transformers are located, shielded in heavy steel cases. They are separated from the rest with a thick plate. There are also four inductors. On a large fully populated board you can see five voltage regulator circuits per channel. Each of them has a slightly different rectifier diodes and capacitors. It looks as if they have been selected for sonic qualities. Specification (according to the manufacturer) Preamplifier Type: Dual Mono/Dual Chassis Voltage Gain: 14 dB or 20 dB (selectable) Rated Input: 12 Vrms Rated Output: 30 Vrms S/N Ratio Reference: > 120 dB Frequency Response: 2 Hz-100 kHz (+0 dBA; -0,5 dBA) THD + Noise: < 0,06 % Channel Separation: > 90 dB Price (in Poland): 245,000 PLN
TENOR INC. MADE IN CANADA
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