In article , Don Pearce
wrote:


It is all about slew rate limiting - that is the mechanism that gives
rise to transient intermodulation distortion. You do, as you say, have
to make some assumptions about maximum levels and maximum frequencies.
With a digital source you can do that with a high degree of confidence,
but with an analogue one, there is always the opportunity for stuff to
be outside your assumed limits.

In practice, simply putting a passive LPF before the amp input resolves
that problem as it defines the maximum possible slew rate for a signal
whose amplitude would not also clip the amp. This is a trivially easy
'solution' that designers did almost without debate long prior to Otala's
publications and talks.

Although his ideas made a 'splash' in places like audio mags, my impression
what the most experienced designers thought he was making a mountain out of
a molehill and getting publicity for sticking a new label on a long-known
behaviour.

Out of curiosity I checked my texts by JLH and Self. JLH gives one brief
para to Otala. Self essentially dismisses him with a comment referring to
one of his papers.

Slainte,

Jim

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