Lexicon M300L, Owner'S Manual

Page: 15 / 162

Lexicon
1-8
300L Owner's Manual
-24 18 12 6 0 6 +12 ovld dB
L
R
Setting Analog
Audio Levels
When shipped from the factory, the 300L is set for Analog I/O configuration.
Once you have connected the analog inputs and outputs, you should set up the
analog input (pre A/D converter) and analog output (post D/A converter) levels.
First, you will need to select a Setup which represents a digital “straight wire”
through the box. To do this, press the SETUP key, then use the PRE slider to
select Setup Preset 81.
The upper display should read:
STEREOADJUST
SG: SET P 81
Press ENTER to load the setup. Press CTRL, then press PAGE, followed by the
number 9. This will display Control Mode Page 9. The lower display will show:
IN: LFT RT OUT: LFT RT
The I/O structure of the box is specified such that if a +11dBu signal is input into
the box, full scale conversion will occur. This is indeed true if the LFT (left) input
and RT (right) input sliders are set to 0dB. In fact, with the Output sliders set to
0dB, you should read exactly the same, +11dBu. In practice, analog I/O interface
levels vary widely with various console types. The Input and Output controls on
page 9 allow the 300L to be optimized for use throughout the analog world.
With the Left and Right sliders fully attenuated to -10dB, the 300L can look at
signals as high as +21dBu. For those of you who like to “blast” through an analog
console, this full attenuation may be a requirement.
If your console typically sends a +4dBu signal when the send meters read 0VU,
the 300L’s input will be left with only 7dB before converter saturation. This is not
good. A common rock and roll soution would be a quick trim of the send
host
by
-7or -10 dB to give the system a little more “breathing room”. Some analog
engineers often refer to this “breathing room” as headroom. Technically , there
is no such thing as headroom in a digital system. When the converter goes to full
scale, overload will occur. Although the rock ‘and roll solution will usually work,
but we suggest you trim the inputs to the 300L.
To do this, move the LFT and RT input sliders to the required settings. You may
need to “null” these sliders at their mid-travel points in order to “grab” the default
value of +0dB. Attenuate them one at a time and make sure they are matched.
Pressing the buttons under each of the active sliders will interrogate the current
values.