Propeller Head Plaza

Technical and scientific discussion of amps, cables and other topics.

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RE: Phase Distortion, dv/dt, and Slew Rate

Posted by Dave_K on December 21, 2015 at 07:29:05:
The math seems to indicate that the only waves which will add coherently are harmonics that are time aligned, i.e. harmonics from a single instrument or voice. The voices in a chorus will add incoherently, so the total acoustic power will be the sum of their individual acoustic powers.

Measurements of crest factor indicate that the pathological cases you're thinking of don't really happen, or at least they are so rare that they aren't a factor in recording. The highest observed crest factors are from impulses generated by percussive instruments, not from massed voices.

Anyway it's a moot point with modern solid state amplifiers because most are capable of slew rates faster than the product of their rail voltage and max frequency, which guarantees that they can't be driven into slew rate limiting with any input. That was not the case back in the 1970s when Walt Jung was writing about slew rate distortion, when amplifier slew rates were 1-2 orders of magnitude slower than today.