Extron Electronics DMP 128 User Guide - Manual (Page 108)

setting input gain
Floating point DSP technology is internally more flexible than fixed point. However, the
input ADCs and output DACs always run as fixed point, so it is important to optimize
the audio by setting the input level as close to 0 dBFS as possible. This maintains the
resolution at 24-bit. Within the DSP it is not critical to maintain audio levels at 0 dBFS in
order to secure the resolution at 24-bit.
Input gain is set using the intended input source device and typical source material. When
source material is not available, it can be set using pink noise obtained either from a
pre-recorded track on a DVD or CD, or a signal generator.
For program material, set the input gain level (see figure 63, a on the previous page)
so the meters reach approximately – 15 to – 12 dBFS, with peaks at approximately
– 5 to – 3 dBFS. This setting provides enough headroom to accommodate transients or
unanticipated loud events in the program material to avoid possible clipping.
Use pink noise recorded at – 20 dBFS. If the player has an output level setting control,
set the output of the player to maximum, or 0 dB of attenuation. If the maximum output
setting provides gain, then back off slightly from the maximum setting. Using a signal
generator, set the output at – 10 dBu. Whichever pink noise source is used, set the input
gain in the DSP Configurator so the input meter reads – 20 dBFS.
setting a nominal output Level
In order to set up a gain structure to include signal processing, listening to the audio can
be advantageous. Route the audio that carries program material from the source to the
speakers in the room. With the output volume control (see figure 63, e on the previous
page) set to – 20 dB, set the external amplifier so the source material plays at a volume
level that is reasonably loud but tolerable.
notE: Using the volume control for this purpose, set post-mixer trim (see
figure 63, d on the previous page) to 0 dB. Using the post-mixer trim for this
purpose, set volume to 0 dB (100%).
Verify the amplifier is not clipping by observing the amplifier clip indicator. This sets the
amplification/volume nominal level of the system, and if desired, allows listening while
making adjustments. Adjust or mute the volume control as necessary
(see
Setting volume Control for the Amplifier Stage on page 104).
DMP 128 • Software Control 102