There's no accounting for taste, or so the truism goes. But arguing over preferences is exactly what many audiophiles do. Similarly, Stereophile reviewers are all about parsing and evaluating sound, and how a product looks isn't usually a big part of the equation. But I'll buck that convention and say that the radically shaped Estelon X Diamond Mk IIs aren't just the…
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Taste is a funny thing. Love cilantro? Millions swear it tastes like soap. Similarly, design cognoscenti will gush over a minimalist Scandinavian sofa that others dismiss as just a pricey plank with delusions of grandeur.
As recommended by Aldo Filippelli, Estelon's amiable VP of sales and business development for the Americas, I had intended to drive the Estelons with the new Vitus SM-025 monoblock amplifiers, at least for a spell. He feels that pairing the Baltic beauties with the Danish power amps results in unusually good synergy. The release of the Vitus product was postponed, however, which frankly made my job a little easier. I used my reference Krell FPB-200c amplifier, a known quantity instead of a wild card. For most of the duration, my hyperclean Benchmark HPA4 line stage served as a preamp.…
Sidebar 1: Specifications
Description: Three-way bass-reflex loudspeaker. Drive units: 11" ceramic-sandwich dome woofer, 7" ceramic-membrane mid/woofer, 1" inverted diamond-dome tweeter. All drivers by Accuton. Crossover frequencies: 75Hz (third-order), 2kHz (second-order). Frequency range: 22Hz–60kHz. Impedance: 6 ohms (minimum 3.8 ohms at 55Hz). Sensitivity 88dB/2.83V/1m. Recommended amplifier power: 50Wpc or more.
Dimensions: 54" (1370mm) H × 17.5" (450mm) W × 25" (640mm) D. Weight 190lb (86kg) each.
Finish: Black Lava Liquid Gloss, White Gloss. Add up to $8000 for nonstandard…
Sidebar 2: Associated Equipment
Digital sources: 15" MacBook Air M2 Max running Roon 2.0, Roon ROCK (Lenovo ThinkCentre), Eversolo DMP-A8, Grimm Audio MU1, Aurender A20.
Preamplifiers: Benchmark HPA4 line stage, Eversolo DMP-A8.
Power amplifier: Krell FPB-200c (recapped).
Integrated amplifiers: Audia Flight FLS10, Pathos InPol Legacy.
Loudspeakers: Focal Utopia Scala EVO, REL No.31 subwoofer ×2.
Cables: Speaker: AudioQuest Thunderbird Zero and Bass. Power cables and interconnects: RSX and Clarus Crimson pure copper OCC power cables. AudioQuest WEL Signature (AES3),…
Back in 2016, I documented the rise of class-D amps using the early TriPath technology. Used in the Bel Canto eVo 200.2, TriPath cracked open the door to the High End but was never admitted due to a dim and opaque treble. The second wave was based on B&O's ICEpower technology, again via a Bel Canto amplifier, the Ref1000M monoblock. ICEpower had more credibility and was accepted by many but, often, only with, ahem, due consideration for size and efficiency. There was an explosion of new class-D amps in 2016 when Stereophile featured glowing reviews of Bel Canto's e.One Ref600M monoblock,…
Let's get to it
It's hard to deny that the Buckeye's specifications seem to conflict with its modest physical size and weight (slightly larger than the Benchmark but considerably lighter), so I immediately chose to stress the monoblocks with organ music, just to relieve some of that cognitive dissonance. That meant starting with two of my familiars from New England: Pipes Rhode Island (16/44.1 rip from CD, Riago CD 101) and (from Massachusetts) Mendelssohn: Six Organ Sonatas, Op.65 performed by Thomas Murray (CD, Raven 390, rip originally from LP, Sheffield Town Hall S-13). I chose…
Sidebar 1: Ultimate Class-D
There's a clear evolution in technology and performance from Hypex's original and innovative "self-oscillating" UcD through to NCore and now to the Purifi Eigentakt class-D module used in the Buckeye amplifier. The original UcD circuit married an input comparator, a power stage, and LC filter with feedback looped back between output and input "undoing" enough of the LC filter's phase shift to ensure stable operation. Loop gain was a respectable 30dB, but designer Bruno Putzeys has said this was as far as he could go and still guarantee the amp's stability.…
Sidebar 2: Specifications
Description: Monoblock power amplifier based on Purifi 1ET9040BA C500 class-D technology. Inputs: 1 XLR (balanced). Input impedance: 51k ohms. Gain: 25.5dB (High), 20.5dB (Medium), 15.5dB (Low). Input sensitivity for rated output (High, Medium, Low): 2.9V, 5.2V, 9.2V. Rated output power at 1kHz (0.1% THD): 375W into 8 ohms (25.75dBW), 750W into 4 ohms (25.75dBW), 1200W into 2 ohms (24.8dBW). Maximum output current: 40A. Power efficiency: 96%. Frequency range: 0Hz–80kHz. S/N ratio: >140dB. THD: 0.0001% (20Hz–20kHz, 400W, 4 ohms). 12V trigger in/out, Auto-Sense…
Sidebar 3: Associated Equipment
Digital sources: Custom Intel/Win11 music server running JRiver Media Center v33 and Roon 2, Merging Devices Hapi II, exaSound S88, Okto dac8 Pro D/A processors. QNAP TVS-873 NAS. Oppo Digital UDP-103 universal disc player.
Power amplifiers: Benchmark AHB2, NAD M23.
Loudspeakers: KEF Blade Two Meta with IsoAcoustics GAIA II feet.
Cables: Digital interconnects: Mogami Gold AES TD DB25-XLR snake. Analog interconnects: Mogami Gold AES TD DB25-XLR snake, Benchmark Studio&Stage XLR-XLR. Speaker cables: Blue Jeans Canare 4S11.
Accessories:…
Sidebar 4: Measurements
I performed a complete set of measurements on one of the Buckeye Purifi 1ET9040BA amplifiers. I primarily used my Audio Precision SYS2722 system, repeating some of the testing with the magazine's higher-performance APx555 system. Because class-D amplifiers emit relatively high levels of ultrasonic noise that would drive my analyzer's input into slew-rate limiting, I inserted an Audio Precision AUX-0025 passive low-pass filter between the test load and the analyzers. This filter mitigates noise above 80kHz and eliminates noise above 200kHz that would otherwise drive…