I don't know anything about the Optimod 9100B, do you know what the
various curves look like?

The graph is a bit messy, but here are the 9100B's pre-emphasis
curves:

http://ourworld.compuserve.com/homep...s/opt-emph.gif

The "Red", "Yellow", and "Green" curves are all continuously variable
from 0 dB (flat) to a maximum of 22 dB boost (at 10 kHz). This graph
shows what each of these three curves look like at boost values of 5,
10, 15, and 20 dB. Meanwhile, the "Blue" NRSC curve maxes out at a
boost of 10 dB, as shown, which meets the NRSC pre-emphasis standard
exactly.

The Optimod 9200's factory-configured pre-emphasis is equivalent to
the "Red" curve at 10 dB boost -- in other words, the first curve on
the graph above the NRSC curve.

I wonder if it is "extreme amounts of pre-emphasis", or just the extra
midrange range hump in the 3.5 to 4 kHz area that you are hearing?

The amount of increased boost extends all the way to 10 kHz,
regardless of which non-NRSC curve is selected, so even the higher
frequencies (which only "wideband" receivers can fully discern) are
increased as well.

Why not just equip your radio with a complimentary four color equalizer
switch?

Because I shouldn't have to. FM radio, TV audio, phono records, audio
tapes, and even CDs all use standardized pre-emphasis curves, with no
user interaction required. Why should AM radio be the same? Canada
made the complete NRSC standards, including pre-emphasis, mandatory
for all of its AM stations in 1988. But the FCC chose to keep the
NRSC standards "voluntary" in the USA, except for a rather lenient RF
spectrum occupancy mask which effectively limits transmitted bandwidth
to +/- 10 kHz (but yet has allowed the disastrous +/- 15 kHz IBOC
system to be used, since its sidebands conform to this RF mask which
was never intended to accomodate digital signals).

The primary goal of the NRSC was to encourage the manufacture of
high-quality AM receivers, by reducing adjacent-channel interference
and providing a "level playing field" of how AM stations broadcast
their signal. Today, unfortunately, these high-quality receivers may
be few and far between, but that does _not_ mean that this kind of
"every man for himself (or station for itself)" attitude should
prevail!

p.s. One correction: The Omnia 4.5AM processor does indeed provide
pre-emphasis that conforms to the NRSC curve. However, if desired,
the user may provide extra mid-range or treble boost by using the EQ
controls.