In article , Don Pearce
wrote:
On Thu, 08 Feb 2007 09:27:23 +0000 (GMT), Jim Lesurf
wrote:



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.

LPFs are good, but not much loved by manufacturers who play the numbers
game in their sales literature.

That may well be so. However if the amplifier is good enough it is quite
possible to use a filter whose passband extends to high frequencies. The
problem of omitting any such passive i/p filter is that you expose the amp
to 'RF' injection by that route, and risk problems no matter how good the
design in other respects.



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.

I suspect Otala was doing no more than voicing facts that everybody
already knew.

That is certainly my recollection.

IIRC the 'TID affair' appeared a couple of years before I started working
as a designer, so I mainly experienced it via consumer mags when he made
the claims, and then becoming personally involved a couple of years later.
However it was rapidly clear that he'd essentially just re-named something
which people already knew about and knew how to deal with if they were
capable engineers. Hence when I became involved in the biz I swiftly found
out that the designers I chatted to did not think that much of his work.

Slainte,

Jim

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