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Classé Omega monoblock power amplifier Measurements

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…

The Essex Echo 1995: Electrical Signal Propagation & Cable Theory

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…

The Essex Echo 1995: Electrical Signal Propagation & Cable Theory Page 2

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…

The Essex Echo 1995: Electrical Signal Propagation & Cable Theory Page 3

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…

The Essex Echo 1995: Electrical Signal Propagation & Cable Theory Page 4

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 Essex Echo 1995: Electrical Signal Propagation & Cable Theory Page 5

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.…

The Essex Echo 1995: Electrical Signal Propagation & Cable Theory References & Further Reading

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.

The Essex Echo 1995: Electrical Signal Propagation & Cable Theory Maxwell's Equations

Sidebar 2: Maxwell's Equations

Faraday's Law

Ampere's Law

Gauss's Theorem

div D-Bar = r

No Magnetic Monopoles

div B-Bar = 0

The constituent relationships that define electrical and magnetic material properties are

D-Bar = ε0εrE-Bar
B-Bar = µ0µrH-Bar
J-Bar = σE-Bar (if σ is constant, then this equation represents Ohm's Law)

However, it is common to write ε = ε0εr and µ = µ0µr, thus D-Bar = εE-Bar and B-Bar = µH-Bar
where
E-Bar, electric field strength, (volt/m)
B-Bar, magnetic flux…

Recording of December 2004: <I>SMiLE</I>

BRIAN WILSON: SMiLE
Nonesuch 79846-2 (CD). 2004. Brian Wilson, prod., mix; Mark Linett, eng.; Kevin Deane, Daneil S. McCoy, Pete Magdaleno, asst. engs.; Darian Sahanaja, mix. AAD? TT: 47:01
Performance ****½
Sonics **** (footnote 1)

Give Brian Wilson credit. Few artists, let alone those who've had to do battle with an abusive father, drugs, quacks, chemical imbalances, and the pressure that comes from being, at age 24, a group's sole creative force, would have the guts or the inspiration to return to the scene of their greatest folly. Yet that is precisely what Wilson, 37…

The Fifth Element #19

Let's start with some music—three discs I recently have been using to evaluate equipment as well as listen to for enjoyment. They are as contrasting in style as one could hope for, but all on an enviably high musical plane. (Space considerations compel brevity approaching that necessary to sell screenplays to producers at cocktail parties, footnote 1)

Ensemble Amarcord: And So It Goes (Apollon Classics apc 10102): Former choristers from Bach's own church make up this German version of The King's Singers. This contemporary a cappella program ranges from Billy Joel to Supertramp to a Cuban…