Class D Puzzler Answer
Ok, a number of you were close on the Amplifier Puzzler I presented below. The problem did stem from a voltage related problem, but it wasn't DC offset.
The basis of the Panasonic amplifier is a Class D switching arrangement. By nature, Class D switching amplifiers are formed by integrating the audio sine wave over a high frequency, high amplitude square wave carrier. The result is a Variable Pulse Width, Variable Amplitude output signal. The downside of this arragement is that filtering devices must be present at the output to prevent the high voltage square wave from presenting itself at the speaker wires.
Normally speaking, this HTIB system is connected to a passive subwoofer with enough inductance to interact with the HTIB amplifier and lower the carrier voltage to a safe level (hopefully a few millivolts). So, Panasonic apparently decided that they could skimp on filtering in the HTIB because the design allowed it.
The speaker level input resistors burnt up quickly because the high voltage square wave was allowed to remain. Around 50V, to be exact.
Prevention: A simple pair of low value inductors in series with each lead to the input of the amp would have prevented this problem.
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