Setting Input Gain; Setting A Nominal Output Level - Extron electronics DMP 128 User Manual

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
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, 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
to – 20 dB, set the external amplifier so the source material plays at a volume level that is
reasonably loud but tolerable.
NOTE: To use the volume control for this purpose, set post-mixer trim (see
69,
D
(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
) to 0 dB. To use the post-mixer trim for this purpose, set volume to 0 dB
(figure 69
on page 102,
A
on the previous page) set
E
on page 105).
DMP 128 • Software Control
) so the meters
figure
103