Setting Audio Levels - Lexicon PCM 91 - REV User Manual

PCM 91 User Guide

Setting Audio Levels

1-6
The PCM 91, with both analog and digital input and output connections, requires
some attention to proper setting of signal level.
Analog inputs are first gain-conditioned by the rear panel input gain switch, and
then by the front panel INPUT knob. Proper setting of both the switch and knob
are important for best performance of the A/D converter.
Analog and the selected digital sources are selected in Control mode (0.0 Audio
Input Source). The selections are: 44.1, 48, Ext: XLR and Ext: Coax.
Proper setting of Input level on the PCM 91 is dependent on:
• Proper signal level into the analog front end to avoid signals causing overload
at the DSP input (rear panel Input Level button),
• Proper adjustment of the signal level into the analog-to-digital converter to
optimize noise and avoid overload (front panel INPUT knob),
• Proper setting of signal level into the digital signal processor to optimize noise
(InLvl parameter in each algorithm).
Headroom Display
The headroom display provides both headroom and overload information from
a variety of measurement points. The meters display analog or digital input data,
depending on the selected Audio Input Source (Control mode 0.0).
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.
overload:
acceptable: +20dBu to -2dBu
too low (noisy):
Overload
The 0db (overload) indicators will light under the following conditions:
• A/D overload
• overload at any point in effects processing
• input level within 1dB of maximum
For example, 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.
Unbalanced
>+20dBu
<-2dBu
Lexicon
Balanced
> 0dBu
0dBu to -22dBu
<-22dBu