Solid State Power Amp Reviews

I own and enjoy loudspeakers from seemingly opposite ends of the audiophile spectrum: I'm a huge fan of minimally efficient yet otherwise overachieving flat-panel designs, such as my Magnepan LRS speakers. Yet I'm just as smitten with another, equally outside-the-norm alternative: high-sensitivity full-range loudspeakers, such as my Zu Omens—especially when driven by tube electronics. It's an ongoing yin and yang that keeps my home system in a constant state of flux: Alternating between loudspeakers that use such different technologies, while maintaining relatively optimal positioning for each, is a bit daunting. But there's an even bigger challenge: finding a single amplifier design that's simpatico with both. While tubes would be the obvious choice for the Zu loudspeakers, all-tube amplifiers with sufficient power for my Maggies are definitely outside my fiscal comfort zone.

That's where Minneapolis-based Bel Canto Design comes into the picture. I've heard great things about their class-D solid-state amplifiers for some time, but they've always existed on the periphery for me: I considered Bel Canto amps a bit too esoteric for my relatively utilitarian system. But now's the time to rethink that perspective: With their new e1X product line—a stereo power amp, a preamp/DAC, and an integrated amp—Bel Canto suggests that they're making a generous portion of their top-line technology available at a significant cost savings. Hence this review of their new e1X Stereo Amplifier ($6000), which is priced 40% lower than its predecessor in the Bel Canto Black EX line.

Description
The e1X Stereo Amplifier is indeed a class-D design. Its rated output power is 250Wpc into 8 ohms and 500Wpc into 4 ohms, and e1X is reportedly stable into 2 ohms. The amp also has internal switches to select between 27dB and 33dB of overall gain, when needed to accommodate different loudspeaker sensitivities. The e1X's damping factor is specified as greater than 500, its dynamic range as 126dB. I asked John Stronczer, Bel Canto's founder, CEO, and chief of design, to expound on the class-D technology employed in the e1X, and he responded with the following: "The output stage is a low gain Ncore class-D stage that provides extremely low noise and distortion while delivering up to 30 amperes of current. The overall architecture of this amp (and the other Ncore based products in our line) is a two-stage architecture with no global feedback.

"The first stage delivers most of the gain, either 14dB or 20dB depending on an internal switch setting and operates in class-A mode in the e1X amp. The second stage is the Ncore modulator that delivers all of the current to the speaker load and has a gain of 4.5× or 13dB. The first stage amplifier is our proprietary discrete Single Stage High Current class-A amplifier and uses selected resistors and capacitors for best performance. The signal path from the input stage through the Ncore modulator stage is fully discrete. There's more than 50dB of loop gain throughout the audio band in both the input and the Ncore modulator stages. The result is a constant low-distortion signature throughout the audio band and none of the coloration that can occur when feedback is used without adequate bandwidth or loop gain in the amplifier stages."

Stronczer also noted that the 100kHz switching power supply employed in the e1X is one of the key reasons for the relatively low mass of the amplifier (see below). The power transformer only weighs about a pound, compared with the typical 20lb (or more) of conventional 50/60Hz transformers used in some class-AB and class-A amplifiers. He continued: "The 100kHz operating frequency . . . results in lower magnetic core loss (a smaller core) and much lower copper loss in the transformer. This also results in better supply regulation under loading, and better response to dynamic load changes. This supply also does not suffer from the typical 50/60Hz harmonic noise radiation that can color the midrange of many audio amplifiers. The resulting midrange clarity is proof of this approach." Stronczer also mentioned that class-D output stages don't suffer from the typical thermal wander effects that can color the sound of more conventional class-AB designs.

I also asked Stronczer how they managed to get the price down to $6000 vs the $10,000 price of its counterpart in the pricier Black EX line. He told me that while the internal circuitry of the e1X shares much of the Black EX amp's goodness, there were certain design constraints necessary to lower the price. Principally, the more expensive Black EX amplifier is a higher-powered design, rated at 700Wpc (4 ohms) vs the e1X's rated 500Wpc into the same load. And the Black EX amp is a true dual-mono design, with independent 1200W power supplies and signal paths for each channel. A higher grade of silver/gold wiring is employed in the EX series, and the chassis and case design uses machined aluminum plates and is substantially more robust. But John assured me that, despite significant differences between the two amps, the overall gestalt of Bel Canto's other amplifier offerings is definitely present in the e1X.

Setup and installation
When the e1X arrived, I was immediately struck by how very light the shipping box was: The combined weight of amplifier and carton is only 18lb! In addition to being lightweight and relatively compact (17.75" wide × 15.75" deep × 3.25" high), the e1X has a spare, uncluttered rear panel, with connections as expected: single-ended (RCA) and balanced (XLR) inputs, stereo pairs of WBT Nextgen loudspeaker connectors, and an IEC socket for the AC cord. Michael McCormick, the Bel Canto's president, mentioned that the company has no specific recommendations with regard to power conditioning, in the absence of which my best bet would be to connect the amp directly to the wall. My listening room has dedicated AC outlets for audio equipment (10-gauge Romex, Hubbell outlets); I used a custom Rite Audio Cables High Current Sound Pipe AC cable to supply power to the e1X. The amp has a rear-panel main power switch, and there's also a standby switch on the front panel.

McCormick suggested that I first make all the necessary equipment connections, then allow the amplifier to warm up and burn in for a minimum of 72 hours before doing any critical listening. After unboxing, I took the e1X downstairs and swapped it in place of my Emotiva XPA-1L monoblocks—and in doing so, I noticed what might be perceived as a bit of a problem: The Bel Canto's casework is so incredibly lightweight that unwieldy, cumbersome cables, such as my MG Audio Planus II loudspeaker cables, actually pulled the e1X back and forth across the amp stand. (Note also that the speaker connectors for both channels are at the same end of the e1X's rear panel, apparently done to maintain short signal paths in this non-dual-mono design; that too made connections with bulky cables a little more difficult than the ideal.) Even my AudioQuest Yukon XLR interconnects had the amp sliding all over the place. I wondered if something even pointier (or gripper) than the e1X's conical footers might make it less prone to movement.

This e1X generated negligible heat and could surely be left powered on.

Listening with the Magnepan LRS
There's a cult following in the audio world for small Maggies such as the LRS ($650/pair), and I count myself among the faithful. Some of us feel that the only thing separating the LRS from Magnepan's more expensive offerings is careful amplifier matching—that and perhaps a few well-chosen tweaks. As for the latter, I upgraded my pair with a set of third-party custom stands from Magnarisers.com: They've made a tremendous difference in the performance level of the LRS.