It took some time to figure out why, in the middle of auditioning Rotel's Michi S5 stereo power amplifier ($7499.99) with the room-shaking opening of Richard Strauss's Also Sprach Zarathustra, Ravel's far subtler and perfumed setting of Tristan Klingsor's lyrics from Shéhérazade came to mind. And then the pathway opened: As mundane a task as reviewing a component may be—listen to this, listen to that, compare to your reference, take copious notes, ponder, and proceed—we music lovers perpetually long for more. We want to be seduced by music and soar aloft on its wonder. We want to transcend routine, rise above the commonplace, and experience the beauty that can rise amidst the ashes. We want to fly.

Is that too much to ask of a dual-mono, class-AB amplifier that, despite its 132lb, 1200W power consumption and continuous power output of 500Wpc into 8 ohms (and 800Wpc into 4), costs considerably less than many of its rivals? Shouldn't I be setting my sights a bit lower than flying—maybe content with a good walk on a nice spring day?

That's when I realized what Ravel and Klingsor's visionary exoticism was telling me. I hadn't decided to do anything. The Rotel Michi S5 had taken charge, and the music had done the rest. All I had to do was open my inner eye, close my outer eyes, and surrender to the beauty that had engulfed me unexpectedly.

I shouldn't have been surprised. A year ago, when Michael Fremer reviewed the monoblock version of the S5, the Rotel Michi M8, he wrote about how much fun he had listening. He loved it. And here I was, having the same experience. I didn't want to take notes. In fact, what I did write down consumed just half the scrap paper I usually require for note-taking. I just wanted to find more and more time to listen.

Planet Earth, can you read me? Before we listen together vicariously and fly off into the golden sky, let's hang a bit on the physical level. As huge as the Michi S5 is, it's also rather understated and elegant, assuming you don't illuminate the huge front display, in which case you're treated to, in addition to indication of the temperature (in Celsius) of the S5's two sections, various permutations of dB Peak Power Meter and Frequency Spectrum Analyzer. I found the display initially fascinating but ultimately distracting. So, with the aid of the S5's slim, lightweight, equally attractive remote control, I opened the menu, set the display brightness to either "low" or "off," and set "Auto Power Off" to five hours. (The options are disabled, 20 minutes, 1 hour, 2 hours, 5 hours, and 12 hours.)

Positioning the 132lb Rotel Michi S5 atop Nordost Titanium Sort Kones on a Grand Prix amp stand required removing one of my 115lb D'Agostino Progression M550 monoblocks. How grateful I am that more than a year ago, during one of my first runs through these woods, just after I'd passed a man walking in the woods with his wife, I heard the words, "Don't you write for Stereophile?" Those words were spoken by former distributor Scott Campbell, a digital engineer, archivist, and future Zen Priest who is open to complementing daily hours of meditative silence with helping do what needs doing so that we can listen to music to our hearts' content. Thank you, Universe, for introducing me to my new audiophile buddy; it really helps to have someone else to call on.

The S5's rear panel includes a 15-amp IEC power cable receptacle and, right above it, a master power switch. It also holds two cooling fans, which I never heard—I have no idea when they turned on and off, or if they ever did—an RJ-45 port for software updates, 12V trigger in and out, an input selector switch, and an RS232 nine-pin input jack for integration with automation systems.

I ran an Ethernet cable from my network to the S5 and updated system software to the current version. The sole purpose of the software upgrade was to tweak the VU meter on the front panel display. Menu navigation was so easy that I probably could have performed the update without reading the manual, which is accessible either via a supplied USB stick or online.

My reference D'Agostino Momentum HD preamplifier is fully balanced, so I ran XLR interconnects between it and the S5. After attaching speaker cables to one of the S5's two pairs of five-way rhodium-plated binding posts, I connected them to the Wilson Audio Alexia 2 loudspeakers. (The second set of binding posts can be used for subwoofers.) When it was time to transition the unit from standby to on, I either pushed the power button centered beneath the display or used the Power button on the remote control.

A Zoom chat with Rotel Chief Technical Officer Daren Orth revealed the genesis of the current Rotel Michi line. "I challenged our engineers to develop a technology platform, based on Rotel's existing platform, that would push the envelope farther than we had ever done," he said. "We wanted something that could eventually be productized in some form.

"Ultimately, they engineered a performance spec. After they came up with a platform and refined it, we looked back at Rotel's history and found the original Michi series from the 1990s that elevated Rotel to an entirely new level of performance, industrial design, manufacturing methods, and—admittedly—price point. We realized that we had done the same thing close to three decades earlier.

"After examining the design methods used by the old technology team, we looked at new components and new ways of winding transformers and isolating circuits. Then we looked at how and why we have engineered everything and really pushed ourselves to do everything better. For example, we examined the number of output devices and looked at all their aspects, including radiated noise and heat. We also evaluated new materials that might provide greater stability, and then determined the best place for each component."

Once the engineers had come up with a design, they conducted bench measurements to ensure they were within the target range. Next, Rotel's acoustic engineers picked the best-sounding capacitors and other components for the design and dialed in the values; choices were dictated by sound rather than price. Since a component design is holistic—every part and its placement affects the sound of the whole—every circuit was gone over, modified, changed, and remeasured until everyone was satisfied with what they saw and heard.

The S5's twin toroidal 2200VA power transformers, one per channel, are manufactured in-house. Housed in individual, epoxy-filled enclosures designed to eliminate noise and vibration, they lead to four large, British bulk capacitors totaling 188,000µF, which feed 32 high-current output transistors. "Power is easy," said Orth. "You can make power cheap. But controlling the power down to 1 ohm to maintain the integrity of the output over the entire frequency spectrum is not." One part of that is heat dissipation. "We also had to custom-engineer our heatsinks for the right amount of opening and surface area."

Rotel's online materials warn against connecting speakers with an impedance of less than 4 ohms. When John Atkinson measured the Alexia 2 more than four years ago, he wrote, "Its impedance drops to 2.6 ohms at 84Hz, and there is a demanding combination of 5.1 ohms and –44° electrical phase angle at 57Hz, both frequencies in regions where music can have high energy levels." Is there reason for concern? Via a PR rep, Rotel assured Editor Jim Austin there would be no problem connecting the S5 to my power-hungry Alexia 2s. And during our chat, Orth assured me that even though Rotel stipulates output power as 500Wpc into 8 ohms and 800Wpc into 4 ohms, they had measured the amp down to 1 ohm. When I subsequently asked the reason for the company's cautionary impedance message, he emailed back: "The 4 ohms statement represents the certification-rated power impedance at the output spec, knowing the power supply and circuit drives much more demanding loudspeakers."

Log in or register to post comments COMMENTS A thoroughly great review. Submitted by Anton on July 1, 2022 - 11:16am Thank you. Log in or register to post comments