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April 30, 2015


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TOny Stewart

Many many times.

Ceramic is microphonic

Oil insulators in transformers can generate impulse ticks of PD from charge accumulation and breakdown of a microvoid from contaminants.
Similar with dry insulation.

Magnetics are microphonic if they move.....

John Dunn

Hi, Tony.

A number of answers have been offered, but like these, they relate to real world parts that can have parasitic effects from various causes.

The issue at hand is that the L and C elements in this model are all absolutely ideal. They have no contaminants, no stray L or C elements, no leakage and so forth.

Even so, even though the L and C elements are perfectly free of every anomaly imaginable, the circuit model yields a resistive input impedance which, in looking like an R, ought to have Johnson noise, but where would that Johnson noise come from?

I have no explanation for that at all.

Tony Stewart near Toronto,  EE since 1975

I remember hearing running water coming out of my Buck Regulator choke 100uH epoxy sealed. It was PWM mode, but part of the load was boost regulator for biasing a Kopin LCD and driving the analog amps.

Evidently what I heard was a mathematical metastable condition call CHAOS and the microphonics in the coil.

A bigger Cap with lower ESR Fixed it.

Tony Stewart near Toronto,  EE since 1975

but I dont think the distributed impedance of reactive components generates thermionic brownian noise in an ideal transmission line.

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