May: And even the board layout is extremely critical. Minimizing the amount of loops within the grounding circuitry—not ground loops per se, but how the signal flows in the board—is a major problem. A fully differential amplifier, if well designed, is immune to things floating around on the ground because the amplifier is only measuring the differences between two inputs.
Atkinson: Professionals have worked balanced for a long time. Why is it only now that this is being worked into consumer…
Unless otherwise noted, the Sennheiser headphones auditioned here were driven from the analog output of a Krell Reference 64 D/A processor. The transport was a Krell DT-10, connected to the processor by ST optical link with ST sync lock. The interconnects between the processor and headphone interface units were AudioQuest Lapis Hyperlitz, alternated with TARA Labs RSC where noted.
Comparison products included the Stax SR-Lambda Pro Classic, the Koss ESP/950, and Sennheiser's own HD-580 driven by the HeadRoom Supreme dedicated headphone amplifier.—Thomas J.…
Sennheiser Orpheus HE 90 headphones: Open-back, diffuse-field compensated. Transducer principle: electrostatic, push-pull. Frequency response: 25Hz–75kHz, –3dB. Distortion: <0.01% at 94dB, <0.1% at 110dB. Maximum sound pressure level: 118dB. Bias voltage: 500VDC.
Weight (excluding cable): 12.9oz (365gm).
Orpheus HEV 90 amplifier: Tube headphone amplifier (not available separately) with on-board D/A processor. Frequency response: 10Hz–20kHz, –0.25dB. Distortion (1kHz): <0.01%. Input sensitivity: 400mV. Input impedance: 10k ohms. S/N ratio (unweighted…
When the recession hit high-end audio in 1978–80, Bongiorno designed cost-effective versions of his original Sumo amplifiers…
The Andromeda measured less than 0.028% Total Harmonic Distortion plus Noise (THD+N) at its rated power into 8 ohms, and less than 0.053% THD+N into 4 ohms at 324Wpc. The amplifier could not produce more power at 4 ohms, going into mutual conduction when pushed further. (Mutual conduction occurs when the complementary output devices (which normally work in turn) conduct current simultaneously, and thus work against one another, behaving like a partial short circuit across the power supply.) This was evidenced by a sudden increase of current draw, which…
The two-channel stereo amplifier is still the most typical configuration found in most systems, and the Sumo Andromeda II sticks with that convention. While the monoblock is becoming more popular, there's no free brunch; monoblock design results in higher costs to the manufacturer and thus to the buyer, all else being equal.
The Andromeda II is a pure complementary design using full-wave, balanced bridge circuitry. What this means for the user is that there are no common grounds at the output of the…
Associated equipment used in auditioning both of these amplifiers consisted of the Oracle Delphi Mk.IV turntable with SME V tonearm and Dynavector XX-1L cartridge, Sony CDP-X77ES CD player, Wadia WT-3200 transport and DigiMaster X-64.4 D/A converter, and Rowland Consonance preamplifier. Loudspeakers were the Apogee Stages, B&W 801 Matrix Series 2s, and Snell C/IVs. The amplifier was also briefly auditioned through the Nestorovic Type 5AS Mk.IIIs and the PSB Stratus Golds.
Interconnects were AudioQuest Lapis and Cardas Hexlink (the latter from…