In article , (WBRW) wrote:

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.

Thanks for posting the curves. It is not completely clear to me which
ones go together in a family, but from what you are saying, it sounds like
the "color controls the high frequency boost at 10 kHz, and then there is
a separate "mid frequency" equalizer control that controls the bump in the
4 to 5 kHz area?

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.

That makes sense, if I have the right curve that is the one I would
probably choose, either that or one of the others in the group that ends
with 10 dB boost at 10 kHz.

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.

Since when was this the case? The equalization for all these media is
adjusted on the source side to suit what the originator thinks is best.
Why should AM radio be any different?

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

The FCC doesn't even specify pre emphasis for FM except for a maximum that
is allowed, but I don't even see why they bother with that, how can they
enforce it, to really control it they would have to regulate the entire
audio chain back to the original pickup microphone, and even the acoustics
of the original performance venue.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/