Cadillac 1993 DeVille Owners Literature page 158

AM
The range for most AM stations is greater than for FM, especially at
night. The longer range, however, can cause stations to interfere with
each other. AM can pick up noise from things like storms and power
lines. Try reducing the treble to reduce this noise if you ever get it.
This means your radio can produce quality AM sound comparable to FM
stereo. AMAX3 reduces noise without reducing the high frequencies you
need for the best sound. In addition to improved sound quality, AMAX8
includes more station on the AM band. You don't have to do anything in
your radio because AMAX@ is automatic.
AM
Stereo
This means the Delco@ system can receive C-QUAM8 stereo broadcasts.
Many AM stations around the country use C-QUAM3 to produce stereo,
though some do not. (C-QUAM@ is a registered trademark of Motorola,
Inc.) If your Delco@ system can get C-QUAMa, your "STEREO" light
will come on when you're receiving it.
How To Operate Your Sound System
Does your Cadillac have the Compact Disc Music System or an Export
Radio?
If
s o ,
please turn ahead to the part that describes your system. If
a,
please keep reading.