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When Michael McCormick, president of Bel Canto Design, suggested that I review their Black ACI 600 integrated amplifier, I accepted without hesitation. As wonderful as my reference system may sound, its dCS digital front end alone comprises four boxes and a web of cables complex enough to send many a spider spinning. Given the choice between connecting that front end to a pair of expensive, enormous monoblocks—with their similarly expensive AC cords and equipment racks/isolation platforms—or to a single, visually elegant, 45-lb box that costs $25,000, produces 300Wpc into 8 ohms, and requires…
I stuck with the USB-A and Ethernet inputs for digital playback. While I couldn't play DSD128 via USB-A—when I tried, the ACI 600 went silent—I could use Roon to convert DSD128 to PCM 24/176.4 before transmitting it via Ethernet.
Seek and ye shall find
Bel Canto's downloadable Seek iOS app lets you stream music from Tidal to a networked Bel Canto Black system, create and manage playlists, control volume via an iOS smartphone or tablet, and play MQA, DSD, and PCM files from a computer, external drive, or USB stick. Alas, Bel Canto offers but a single page of instructions remarkable…
Sidebar 1: Specifications
Description: Solid-state, class-D integrated amplifier. Digital inputs: AES, S/PDIF, TosLink to 24/192; Ethernet to 24/192, DSD64, MQA; USB 2 to 24/384, DSD128, MQA. Analog inputs: line 1/2, MM/MC phono. Outputs: line/subwoofer, 4.5V RMS; headphones, 4.5V RMS maximum, 32 ohms minimum impedance. Two pairs WBT NextGen five-way speaker binding posts. Power output: 300W into 8 ohms (24.8dBW), 600W into 4 ohms (24.8dBW). Peak output current: 27A. Minimum load: 2 ohms. Frequency response: 0.5Hz–50kHz, ±3dB, all loads. THD+N: 0.001%, 1W, 1kHz, 4 ohms (overall); 0.003…
Sidebar 2: Associated Equipment
Digital Sources: dCS Paganini SACD/CD transport & Scarlatti clock & Vivaldi DAC & Network Bridge network player; Mytek HiFi Manhattan II DAC; Intel NUC7i7BNH computer with 8GB RAM, 128GB SSD running Roon; iPad Pro, external hard drives, USB sticks.
Power Amplifiers: Pass Laboratories XA200.8 monoblocks.
Loudspeakers: Wilson Audio Specialties Alexia.
Cables: Digital: AudioQuest Diamond (FireWire, Ethernet), Wireworld Platinum Starlight Cat8 (Ethernet), Nordost Odin 1 & Odin 2 & Valhalla 2 (USB). Interconnect, Speaker, AC:…
Sidebar 3: Measurements
I measured Bel Canto Design's Black ACI 600 using my Audio Precision SYS2722 system (see the January 2008 "As We See It"). Usually, before I test an amplifier, I precondition it with both channels driving a 1kHz tone at one-third power into 8 ohms for an hour, but this is relevant only for an amplifier with a conventional output stage. As the ACI 600 uses class-D output modules, I began testing it soon after turning it on. However, as class-D amplifiers produce RF noise that could drive my analyzer's input circuitry into slew-rate limiting, I inserted, between the…
Designers of hybrid amplifiers can use solid-state devices in an amp's input stage and tubes in its driver and output stages, as Music Reference's Roger Modjeski did in his RM-200 Mk.II—or they can use tubes in the input and transistors in the output, as Ypsilon Electronics' Demetris Baklavas prefers.
The advantage of solid-state at the input stage can be lower noise. In the RM-200 Mk.II's fully balanced design, carefully matched input devices result in high common-mode rejection and low-noise operation close to the levels achieved with the best input transformers. The RM-200 Mk.II's…
The recording sounds simply miked, à la Decca's microphone "tree," with a strong, stable center image: the piano was locked firmly in place, despite the rich field of reverberation surrounding it, and presented the orchestra convincingly arrayed behind and to the sides of it. The Hyperions' presentation was intensely holographic, and harmonically generous and convincing without sounding overripe. The sensation of "hearing" the air in the recording space produced a strong feeling of being in the Mariinsky Theater during these performances.
Playing an original pressing of Fritz Reiner and…
Sidebar 1: Specifications
Description: Hybrid monoblock power amplifier. Tube complement: one 6H30 Pi or 5687 (input), one 6CA4 or EZ81 (rectifier). Inputs: unbalanced (RCA), balanced (XLR). Output power at 1kHz: 370W into 8 ohms (25.7dBW, (first 100W in class-A), 650W into 4 ohms (25.1dBW), 1150W into 2 ohms (24.6dBW). Frequency response: 6Hz–80kHz, –3dB (input transformer peak: +2.5dB at 50kHz). Voltage gain: 26dB (x20). Input impedance: 47k ohms. Output impedance: 0.3 ohm. THD (1kHz into 8 ohms, 6H30 Pi tube): 0.7% at 100W, 1.2% at 300W. THD (1kHz into 8 ohms, 5687 tube): 1% at 300W.…
Sidebar 2: Associated Equipment
Analog Sources: Continuum Audio Labs Caliburn turntable & Castellon stand; Kuzma 4Point, Swedish Analog Technologies tonearms; Kuzma CAR 60, Lyra Atlas & Atlas SL & Etna & Etna SL, Miyajima Labs Zero (mono) & Madake & Madake Snakewood, Ortofon Anna & A95, Transfiguration Proteus D cartridges.
Digital Sources: Audio Alchemy DDSPro CD transport, Simaudio Moon Evolution 780D streaming DAC, dCS Rossini streaming DAC/CD player, Lynx Hilo A/D–D/A converter, Meridian Digital Media System, Pure Vinyl & Vinyl Studio software.…
Sidebar 3: Measurements
I measured the Ypsilon Hyperion with my Audio Precision SYS2722 system (see the January 2008 "As We See It"). Before performing any tests, I ran it at one-third its specified clipping power into 8 ohms for an hour. At the end of that time the top panel was warm, at 104.4°F (40.3°C), the heatsinks slightly hotter at 109.8°F (43.3°C). With the 6H30 Pi input-stage tube, with which I did almost all the testing, the gain at 1kHz at the speaker terminals was 26.4dB for both the balanced and single-ended inputs. With the alternative 5687 tube the gain was 0.5dB higher.…