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Original Message
RE: -75 dB
Posted by tomservo on June 26, 2014 at 06:46:49:
Hi Tony
Man you are lucky to be working in the digital domain where the noise floor is so low. A -75dB null is very low indeed, if one were using an old style HP analogue distortion analyzer, a -75dB null on a Voltage signal would be unreadable.
Of course there are other complications there too haha.
One thing that was puzzling at first but made sense later was that measuring a low distortion loudspeaker, one needed to subtract the amplifiers voltage and harmonics from the loudspeaker (used vector subtraction with an Hp3562) because the amplifiers harmonics could either add OR subtract from the loudspeakers distortions depending on their phase.
Best,
Tom