Optimizing Audio Levels - Extron electronics DMP 64 User Manual

Optimizing Audio Levels

The DMP 64 uses floating point DSP technology, processing data using a combination of
32- and 64-bit algorithms. The ADCs (analog to digital converters) and DACs (digital to
analog converters) sample at 48kHz, with 24-bit resolution.
With floating point DSP it is extremely difficult to clip the audio signal within the DSP
audio signal chain, after the ADC and before the DAC. That means the audio signal must
not be clipped at the input ADC. Clipping gives audibly undesirable results and once the
audio is clipped at the input there is no way to correct it further down the signal chain. If
audio clipping occurs at the output DAC that is not a result of clipping at the input ADC,
there are ways to address it within the DSP audio signal chain.
The meters in the DSP Configurator indicate clipping at a user-definable point, with
the default setting at -1 dB. This means the meter indicates clipping when it reaches
-1 dBFS, or 1 dB below actual clipping (0 dBFS). Setting the clipping meter below
actual clipping provides a safety net, allowing the user to reduce input gain before
clipping actually occurs. This "safety net" may be increased or decreased by selecting
Tools | Options | Processor Defaults | Defaults | Meter Clipping
Clip Threshold
NOTE: When the
Meters within the DSP Configurator are peak-type meters, referenced to full scale, or
0 dBFS. For the DMP 64 outputs, 0 dBFS corresponds to +21 dBu, the maximum output
level of the device. Maximum input level is +24 dBu. Gain from -3 dB to +80 dB is
applied in the analog domain, while attenuation from -3 dB to -18 dB is applied in the
digital domain. The input meters are post-ADC, while the output meters are pre-DAC.
The remainder of this section will reference the gain, trim and volume controls outlined in
the figure 62.
Figure 62.
to a number between 0 (dB) and -20 (dB).
Clip Threshold
clipping occurs.
a
Gain, Trim and Volume Controls
a
Mic/Line input gain
b
Pre-mixer gain
c
Mix-point gain
d
Post-mixer trim
e
Output volume
is set to 0 (dB), clipping is indicated only when
b c d
DMP 64 • Software Control
, and setting the
e
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