17
AM Style
Welcome to the OMNIA ONE AM!
Don’t let the small single
-rack sized package fool you! Omnia ONE’s new hardware platform allows us to pack
more power in its single rack space than the original Omnia had in three!
This chapter explains generally how to alter the sound of the Omnia ONE AM using the factory presets, and if
desired, using the controls explained in the
Adjust Processing
section of Chapter 4, to alter those presets and create
custom user presets.
Using Omnia ONE
AM with Early PWM Transmitters
Certain
PWM (Pulse Width Modulation)
transmitter designs may exhibit a condition that can be exaggerated by the
extremely dense output of the Omnia.
This condition is often referred to as the “cliff effect”.
These transmitters have a hard time dealing with linear response to high negative modulation levels and may show a
runaway condition when called upon to produce heavy negative modulation approaching 100 percent.
This effect can be seen by applying a steady 1 kHz
tone to the transmitter at slightly less than 95 percent negative
modulation. Observe the modulation monitor closely as you
slowly
advance the modulation level to 100 percent.
If you notice a sudden jump to 100 percent without being able to first get to 97, 98 or 99 percent then you are
experiencing "cliff effect."
Due to
the high processing power of the Omnia, this can result in over the air distortion not caused by the Omnia
itself.
The simple solution is to operate the Omnia so that negative peaks never exceed 90 to 95 percent modulation
. You
will not notice any significant loss of level but will notice a much cleaner and less fatiguing sound. You may of
course make up this modulation loss by operating the Omnia with a slight amount of asymmetric output to achieve
100 percent or more on positive peaks.
You will also find that limiting negative modulation to less than 95 percent will allow much more aggressiv
e
settings on the Omnia without audible distortion.
Furthermore, the design of the average AM receiver can cause noticeable distortion without a
ny added loudness
when dense negative modulation exceeds 95 percent from any modern transmitter. So keeping your negative
modulation below 95% may be a good idea, regardless of the presence of the “cliff effect” in your transmitter.
The Factory Presets
If you go through and listen to all of the included factory presets, you should
get a “feel” for them and
find one to
start with that is close to the sound you are looking for.
Please keep in mind that the “formats” used to name the presets
are only guidelines and are not engraved in stone.
We had to call them something!
Always make sure your input levels and modulation are set properly before beginning your evaluation of presets.
See
Proper Setting of Input Levels
on Page 1
1.
It is also important to adjust the main “Clipper Drive” control (described in Chapter 4) as low
as possible for the
loudness you need for each preset that you try. This is because the “Clipper Drive” controls the primary tradeoff
between loudness and distortion.
Because many of our customers have been asking for an “in your face” preset for AM talk a
nd sports shows, we
have designed several talk/sports presets that really punch it up. We also were asked for presets that would sound
