What to do for an encore if one is Tenor Audio and builds state-of-the-art amplification whose crowning achievement is an acclaimed 350-watt monaural amp? Some might rest on their laurels. If you’re Jim Fairhead (president) and Michel Vanden Broeck (chief designer), you continue to stretch boundaries and challenge the status quo. Isn’t that what leaders and visionaries do in every industry? The Tenor 350M is arguably one of the world’s finest amplifiers. At this level any ‘best’ is certainly a personal and subjective determination. Though in the opinion of many golden-ear audiophiles, Tenor is at or near the pinnacle. As with many great innovators, there is a drive to dream and stretch boundaries. In this case, Jim Fairhead challenged Michel to expand the limits of the 350’s output power. Could the existing design deliver 400 watts or 450 watts? Even 500 watts? If so, would it maintain its rock-solid stability, reliability and sonic attributes? The result of Jim’s challenge is the stunning 350M Haute Puissance (High Power). The 350M HP takes the fundamental design of the 350M and increases power to 500W into 8Ω, 950W into 4Ω and 1'500W into 2Ω. I know that most of us live in the real world. The original 350M is an expensive innovative amp appealing to a privileged few. The thought of reading about upgraded power and cost to an already exotic amp may cause the casual enthusiast to click away right about now to more mundane down-to-earth products. Well, stick with me a little longer. What started out as an exercise in stretching power limits ended up in audibly improving upon an already outstanding product. In the process, it set some new standards and personally redefined how I listen to music. Trust me, there is something very special going on here.

A little background. Tenor Audio was founded in 2000 beginning with a set of OTL amps. Some consider these 15W, 35W and 75W OTL amps to be at the pinnacle of their time. As a retail customer, I purchased a used 75i version. This became my first introduction to Tenor. With twenty tubes, the amps ran hot and my small listening room became a sauna within hours. Yet during those few hours, there was magic. Unfortunately the laws of physics, heat and power limitations precluded a high-powered version. Tenor subsequently developed the 300M as a hybrid to marry OTL magic to real-world power and control. Unfortunately, management issues, capitalization and a faulty output transistor on the new 300M derailed Tenor for a few years. Fast forward to a new well-funded and professionally managed company with a passionate group of audiophile owners led by Jim Fairhead. Voilà, the Tenor Audio company of today.

Interestingly, this is actually the second HP amp. The first was a tweaked version of the 350M using the same components. The new 350M HP ups the ante with new design elements, new components and a new look. Whilst physically maintaining the Tenor family image, it adds a few stunning new visual features. Embedded in the top is an exquisite StarFire crystal plate bathed in blue to match the front logo. From its unique design, wooden fascia and mirror finish to the blue crystal glow, the 350M HP is visually unique. Additionally the insides are outlined with approximately 400 miniature blue LEDs, providing a dramatic internal glow. Describing Tenor’s fanatical drive for perfection could fill a book. Here is but one example. The specific blue color LEDs lighting the front logo were not available in the micro size needed for the inside. They were blue but not the right kind of blue. To exactly match the color, they used RGB lights. If you are concerned about distortion or pollution from the lighting circuit, fear not. Tenor went to extraordinary lengths to shield and filter the lighting circuits, making them sonically transparent. For those anal-retentive souls, a switch disables the lights. From personal experience and testing, I cannot 'hear' the lights. I tried.

The inherent design philosophy between 350M and HP is identical. Therefore, this review is an update and intended to be read in conjunction with the original 2007 review. With that in mind, let’s look at what the new 350M HP brings to the table. Tenor’s quest for more power included four mandatory design considerations: