SB-301 AM tuning

[Joseph Filice]

Hi,

When tuning AM signals with my SB-301 (the AM filter
is installed), if I tune to the center frequency of the
signal, the audio is somewhat distorted.  If I tune off
a kilocycle or so to either side, it sounds much cleaner.
Is this a known "feature" of the SB-301 in the AM mode,
or could I have a problem with the filter, detector or
something related?  Thanks.

Joe Filice KQ6GL