Description: Solid-state monoblock power amplifier with unbalanced (RCA) and balanced (XLR) inputs and two pairs of 4mm output binding posts. Rated output power: 500W into 8 ohms, 1000W into 4 ohms, 2000W into 2 ohms, 4000W into 1 ohm (all 27.0dBW). Sensitivity: 2.25V for rated output, balanced or unbalanced. Voltage gain: 29.0dB. Input impedance: 100k ohms. Output impedance: 0.017 ohm. Frequency response: 20Hz-2kHz, ±0.1dB. THD+noise: 0.002%. S/N Ratio: 135dB ref. rated output (no other conditions listed).
Dimensions: 19.5" (495mm) H by 11.5" (292mm) W by 23…
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Sidebar 1: Specifications
Sidebar 2: Associated Equipment
Analog source: VPI TNT V-HR turntable-tonearm; Grado Statement, Benz Micro L04 cartridges.
Digital sources: GamuT CD 1, Simaudio Moon Eclipse CD players.
Preamplifier: VAC CPA-1 Mk.III.
Power amplifiers: VTL Ichiban and Mark Levinson No.20.6 monoblocks, VAC Renaissance 70/70.
Loudspeakers: Audio Physic Virgo III, Kirksaeter Silverline 60, Castle Severn.
Cables: Interconnect: Nirvana S-X Ltd. & SL, Nordost Valhalla, Audience Au24, AudioQuest Anaconda, Monster Cable Sigma Retro. Speaker: AudioQuest Gibraltar, Silversmith Silver, Monster…
Sidebar 2: Tricks'n'Tweaks
No—I didn't try swapping in nonmagnetic screws in the Omegas' chassis, or suspend them in a pool of mercury, or anything like that. I set them up, turned them on, and forgot about them. But I found, not surprisingly, that they provided a crystal-clear window into whatever else was happening in the system. Any—and I do mean any—changes were immediately and clearly audible. As a result, I was able to quickly and easily tweak my system to a significantly higher level of performance.
I did quite a bit of cable work during the Omegas' stay, and it was always…
Sidebar 3: Measurements
Following the usual IEC preconditioning of running an amplifier at one-third power into 8 ohms for an hour, the Classé Omega's chassis was hot. However, other than the side-mounted heatsink, which was above 60 degrees C, it was not too hot to keep my hand on. An interesting fact emerged from this preconditioning: The Omega's measured THD percentage dropped from an admittedly low 0.005% when the amplifier was cold, to 0.0018% when fully warmed-up.
At 29dB from either input, the Omega's voltage gain into 8 ohms was to specification but slightly higher than…
Editor's Note: The matter of whether—and if so, how—speaker cables and interconnects can affect the sound of an audio system has vexed the audiophile community since Jean Hiraga, Robert Fulton, and others first made us aware of the subject in the mid-1970s. Most of the arguments since then have involved a great deal of heat but not much light. Back in August 1985, Professor Malcolm Omar Hawksford Ph.D (of the UK's University of Essex and a Fellow of the Audio Engineering Society) wrote an article for the British magazine Hi-Fi News & Record Review, of which I was then Editor, in which he…
Okay, so many of you may not have followed the details of the mathematics. Don't worry—it's really only important to appreciate the high-level procedures, namely:
• Commence with Maxwell's equation, from which is derived the generalized wave equation for propagation in a lossy material.
• Guess at a logical solution for a sinusoidal plane wave, knowing that Fourier analysis allows a generalization to more complicated waveforms (at least for a linear medium).
• Show that the chosen solution satisfies the wave equation, where the propagation constants α and β follow as…
As shown in fig.1, a propagating electromagnetic wave consists of an oscillation of energy between the magnetic and electric fields, these akin to kinetic and potential energy in a mechanical system. It is helpful to think of free-space dielectrics and conductors as distributed inductance-capacitance-resistance networks. For example, in a coaxial cable (fig.3), the electric field is everywhere radial, while the magnetic field forms concentric circles around the inner conductor (Ampere's Circuital Law). It is important to note, as commented upon earlier, that the E-Bar and H-Bar fields are…
It must be noted, of course, that the error voltage induced by the changing external field dominates, so this result would be largely masked. (The greater the conductor spacing, the greater the masking.) With loudspeaker cables (greater than, say, 2mm in diameter) that are terminated close to their characteristic impedance, the external fields will contribute minimal error. However, the loss field still produces time dispersion. If the error voltage is to be correctly predicted, skin depth must be included, a simple resistive model being inaccurate. I am not trying to say that this effect is…
The detailed characteristics of the dielectric material are also important, as the model shows that the dielectric supports the majority of the signal during its transportation along the cable (which can take many passes if the cable is not optimally terminated). Dielectric loss has been cited as a contributory factor, which can be modeled as an equivalent frequency-dependent but low-conductivity σd, where σd = ωε (power factor). Power factors vary from typically 0.0005 to 0.05 (see Skilling [2]). The attenuation and phase constants then follow, as αd = 0.05ωε√µ (Power factor) and βd = ε√µ.…
Sidebar 1: References & Further Reading
[1] Magid, L.M., Electromagnetic Fields, Energy and Waves, John Wiley and Sons, Inc. ISBN 0-471-56334-X, 1972.
[2] Skilling, H.H., Fundamentals of Electric Waves, John Wiley and Sons, Inc. 1948.
[3] Larrain, P. and Corson, D., Electromagnetic Fields and Waves, W.H. Freeman and Company, ISBN 0-7167-0331-9, 1962.