1-11
Getting Started
PCM 81
Proper setting of Input level on the PCM 81 is dependent on:
• Proper signal level into the analog front end to avoid signals
causing overload at the DSP input
• Proper adjustment of the signal level into the analog-to-digital
converter to optimize noise and avoid overload
• Proper setting of signal level into the digital signal processor to
optimize noise.
Headroom Display
The headroom display provides both
headroom and overload information from a
variety of measurement points. The meters
display the sum of both the analog and the
digital input data. Examining either the
analog or the digital level alone requires that
the Level parameter of the subject data stream be set to 100%,
while the Level parameter of the other is set to 0%.
The chart below illustrates the adjustment range that will set input
levels for both balanced and unbalanced operation.When a choice
can be made, it is best to operate at the higher amplitude end of
the recommended range to optimize noise performance.
Unbalanced Balanced
overload: >0dBu >+20dBu
acceptable: 0dBu to -22dBu +20dBu to -2dBu
too low (noisy): <-22dBu <-2dBu
Overload
The 0db (overload) indicators will light under the following
conditions:
• A/D overload
• Overload at any point in effects processing
For example, internal peaking of high Q filters, or level buildup
from certain reverberation modes can result in overload, even
when the input A/D or digital receiver data stream is not at full
scale. Such conditions are most often caused by a combination of
extreme parameter settings. Adjusting parameter/level settings can
eliminate these overload conditions.
Selecting a Digital Input Source
1. Press Control.
2. Press Up or Down until the leftmost digit in the lower lefthand
corner of the display is 0.
3. Turn SELECT to 0.0 Word Clock, and turn ADJUST to display
Ext: XLR or Ext: Coax, depending on the input you are using.
Selecting Word Size
1. Press Control.
2. Press Up or Down until the leftmost digit in the lower lefthand
corner of the display is 0.
3. Turn SELECT to 0.3 Word Size, and turn ADJUST to display
desired Word Size.
• When using analog outputs as primary outputs, set Word Size
to 20 bits.
To Next Page
Loading...
