I haven't waded through it yet but this guy wrote his Masters thesis on the subject.
ABSTRACT
A NEW METHODOLOGY FOR AUDIO FREQUENCY
POWER AMPLIFIER TESTING BASED ON PSYCHO-ACOUSTIC
DATA THAT BETTER CORRELATES WITH SOUND QUALITY.
By
Daniel H. Cheever
University of New Hampshire, December 2001
There exists general agreement that the commonly accepted test and
measurement protocols for audio frequency power amplifiers fail to correlate with the
subjectively accessed devices sound quality. A review of the history of audio testing was
undertaken to reveal if prior art has produced tests that better correlate with sound
quality. A universal concept emerged, one that calls for stronger weight of the higher
order, more aurally discordant harmonic distortion products, over the low order, more
benign harmonics. Separately a study of the psychoacoustics of the ear resulted in a
mathematical derivation of the ears intrinsic aural distortion. The two are combined and
offer a methodology for weighing the harmonics based on a dimensionless figure of merit
that quantifies the amplifier’s harmonic distortion envelopes departure from the ears aural
masking, named Total Aural Disconsonance or T.A.D. It is shown both analytically and
through actual device measurements that the application of negative feedback, regardless
of level, results in poorer T.A.D. figures. Two amplifiers of opposing standard
measurement results are fully tested and subjectively analyzed and results show that the
T.A.D. method outperforms classic T.H.D and I.M. for characterizing amplifier quality.
ABSTRACT
A NEW METHODOLOGY FOR AUDIO FREQUENCY
POWER AMPLIFIER TESTING BASED ON PSYCHO-ACOUSTIC
DATA THAT BETTER CORRELATES WITH SOUND QUALITY.
By
Daniel H. Cheever
University of New Hampshire, December 2001
There exists general agreement that the commonly accepted test and
measurement protocols for audio frequency power amplifiers fail to correlate with the
subjectively accessed devices sound quality. A review of the history of audio testing was
undertaken to reveal if prior art has produced tests that better correlate with sound
quality. A universal concept emerged, one that calls for stronger weight of the higher
order, more aurally discordant harmonic distortion products, over the low order, more
benign harmonics. Separately a study of the psychoacoustics of the ear resulted in a
mathematical derivation of the ears intrinsic aural distortion. The two are combined and
offer a methodology for weighing the harmonics based on a dimensionless figure of merit
that quantifies the amplifier’s harmonic distortion envelopes departure from the ears aural
masking, named Total Aural Disconsonance or T.A.D. It is shown both analytically and
through actual device measurements that the application of negative feedback, regardless
of level, results in poorer T.A.D. figures. Two amplifiers of opposing standard
measurement results are fully tested and subjectively analyzed and results show that the
T.A.D. method outperforms classic T.H.D and I.M. for characterizing amplifier quality.
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