Description: Remote-controlled, fully balanced, vacuum-tube preamplifier. Tube complement: eight 6922 dual-triodes; in power supply, one each 5AR4, 6L6GC, and 6922. Voltage Gain: 18dB balanced, 12dB single-ended. Frequency response: 0.5Hz-60kHz, +0/-3dB at rated output. Hum and noise: 20µV RMS residual IHF-weighted noise output with gain control set to its minimum (100dB below 2V RMS balanced output, 97dB below 1V RMS SE output). Distortion: 0.015% at 2V RMS balanced output. Output impedance: 400 ohms balanced, 200 ohms single-ended. Recommended load: 20k ohms…
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Sidebar 2: Associated Equipment
Analog sources: Simon Yorke turntable, Graham 2.0 and Immedia RPM2 tonearms; Rockport Technologies System III Sirius record player; Lyra Helikon, van del Hul Black Beauty Colibri cartridges.
Digital sources: Musical Fidelity X-Ray CD player, Marantz DR17 HDCD recorder, EAD DSP-9000 Mk.3 DAC.
Preamplification: Audio Research Reference and Zanden phono stages, Lyra Arion step-up transformer, Ayre K-1x preamplifier.
Power amplifiers: Musical Fidelity Nu-Vista 300.
Loudspeakers: Sonus Faber Amati Homage, ProAc Future 1.
Cables: Phono: XLO…
Sidebar 3: Measurements
I measured the performance of the Reference Two in both full single-ended and full balanced modes. Maximum voltage gains were 15.2dB balanced in to balanced out, and 13.8dB single-ended in to single-ended out. With a single-ended input, the maximum gain available from the balanced outputs was just under 20dB. The preamp was non-inverting from both sets of outputs. The unity-gain settings of the volume control were 2:00 balanced, 2:30 unbalanced.
The preamp's input impedance varied from 52.5k ohms (unbalanced at 20kHz) through 66.5k ohms (unbalanced, bass…
Intermodulation distortion in either mode was very low. Fig.6 shows the balanced result at 2V output into 100k ohms; the 1kHz difference tone lies at a low -80dB (0.01%).
Fig.6 Audio Research Reference Two, balanced HF intermodulation spectrum, DC-22kHz, 19+20kHz at 2V into 100k ohms (linear frequency scale).
Finally, the Reference Two can output very high levels of low-distortion signal into high impedances. Fig.7 shows the THD+noise percentage plotted against balanced output voltage into 100k ohms (bottom trace) and 600 ohms (top trace). The preamplifier doesn't clip (…
The word on Bel Canto's upsampling DAC was already out when I visited their room at the 2000 Consumer Electronics Show looking to get one of the first samples. But despite my protestations, all Bel Canto's Mike McCormick wanted to talk about was their company's new digital amp, the eVo 200.2. Sure, there's a future out there in which all sources will be digital and D/A conversion will occur in the speaker (or later?). But today, I see no practical advantage in a digital amplifier with only an analog input. It may be more efficient and it may be new technology, but the amplifier has got to…
Switch the amp on from the rear, wait a few seconds for the relay to click gently, and there's music. The simple and clear manual was hardly needed except to confirm that the amp is intended to remain powered up. With any of the inputs and any of the speakers I tried, the case of the eVo remained cool to the touch.
I inserted the eVo in my main system in place of the resident McCormack DNA-1 (Rev.A mod) and listened. Ho-hum. The eVo sounded kinda flat in perspective, and thin—not bad, but it seemed in great need of run-in before facing judgment (Bel Canto suggests at least 40 hours).…
In the home, we turn up the volume to make the audible image of the performance seem larger and, as a direct consequence, the performers nearer. This maneuver should not make the performers sound as if they're playing louder, because the true loudness of the performing instrument is encoded into the recorded harmonic content and dynamic emphasis. At least, this has been my experience.
That's not what I heard from the eVo 200.2. When I turned up the EVo's wick, everything got louder, but not much closer. The eVo forced me to find the one volume level that suited the sound captured on the…
Sidebar 1: Specifications
Description: Solid-state, two-channel power amplifier with "class-T" output stage and two pairs of multiway binding posts. Inputs: 1 pair line-level RCA, 1 pair line-level XLR. Continuous power: 120Wpc into 8 ohms (20.8dBW), 200Wpc into 4 ohms (20.dBW), 1% THD+N. Up to 800W short-term continuous, mono. Input sensitivity for full output: 2V RMS. Input impedance: 20k ohms. Distortion at 1W, 1kHz: 0.01% low-order harmonic, 20kHz measurement bandwidth. Bandwidth: -3dB at 1Hz, 80kHz. S/N Ratio: 96dB A-weighted, ref. 1W out. Stereo mode voltage gain: 23dB. Damping…
Sidebar 2: Associated Equipment
Analog source: Heybrook TT2 turntable, SME III tonearm, Ortofon SME30H cartridge.
Digital source: Meridian 508-24 CD player, Meridian Reference 800 DVD/CD player, Mark Levinson No.360 D/A processor.
Preamplification: Sonic Frontiers Line-3, Blue Circle BC21 preamplifiers; Margules/Magenta FZ47dB phono stage.
Power amplifiers: Blue Circle BC22, Bryston 9B-ST THX, McCormack DNA-1 (with Rev.A mod), Sonic Frontiers Power-3.
Loudspeakers: Revel Ultima Studio.
Cables: S/PDIF Digital: Apogee Wyde-Eye, Illuminations D-60. Interconnects, DAC-Preamp:…
Sidebar 3: Measurements
Despite its high efficiency, the chassis of the Bel Canto eVo 200.2 was warm after the one-hour preconditioning period at one-third power, though not nearly so warm as would be the chassis of a traditional amplifier with a class-AB output stage. The voltage sensitivity into 8 ohms was low at 24.2dB with both balanced and unbalanced inputs. The single-ended input impedance was a high 109k ohms, this approximately doubling for the balanced input. The amplifier was polarity-correct via both inputs (the XLRs are wired with pin 2 "hot").
The source impedance…