On Tue, 11 Oct 2005 22:58:48 GMT, "
wrote:

Years ago I read about something called a null speaker test.

It was a way to detect differences between amps by connecting 2 amps to a
single speaker. If there were differences between the 2 amps then the
speaker would generate sound.

Does anyone know of this test and can you give details?

That's extremely likely to destroy *both* amplifiers. The classic null
test uses an attenuator at the output of the amp, exactly matched to
the gain and phase characteristics of the amp, and the output of the
attenuator is then summed with the input signal. the output from this
summing junction will be any amplifier artifacts.
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Stewart Pinkerton | Music is Art - Audio is Engineering