THD meter circuit needed

Tim Ressel Tim_R1 at
Fri Aug 11 22:30:04 CEST 2000

I just did a survey of the (unknown, random) sound card in my PC, using
Spectra+. I get a noise floor of -90 dBr relative to max sig (i think). This
cooresponds to a minimum of 0.0032% (again I think) distortion. The noise floor
gets down to -100 dBr above 700 Hz if you ignore (or average out) an annoying
bump at 16,500 Hz.

Point is: I think sound cards do better than people are giving them credit for,
and a second look is deserved.

Tim Ressel--Compliance Engineer
Verifone Division
3755 Atherton Rd.
Rocklin, Cal
timothy_ressel at

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