FRONT PANEL CONTROLS
(top & bottom rows)
IN/BYPASS
This switch (2 each) is a "true-hardwired" bypass, making a straight connection from input to
output allowing for accurate comparison of source and processed audio. BYPASS will work,
even if the L2M is off or unplugged from the A/C mains.
IN/BYPASS - OPERATIONAL NOTE:
For accurate perception when comparing processed audio to source material, it is essential that
make-up gain be correctly adjusted. The L2M has 2 points to which MAKE-UP GAIN can be
applied: OUTPUT LEVEL and LIMITER FEEDBACK. For more detail, see OPERATIONAL
NOTES - OUTPUT LEVEL and OPERATIONAL NOTES - LIMITER FEEDBACK. For purposes
of A/B listening STEREO LEVEL RIDE should be at it’s UNITY position.
OUTPUT LEVEL
Output level/make-up gain is accomplished using a precision 24-step attenuator (one for each
channel). Range of settings is from -6dB to +17dB in 1dB increments. As an initial setting for the
OUTPUT LEVEL attenuator, be sure the UNITY position is selected (both channels) and all
other controls are in their “OFF or UNITY” position. Verify that switching between IN & BY-
PASS exhibits no change in volume. This can be confirmed by injecting a 1-kHz tone and ob-
serving an outboard DMM or other suitable meter. The L2M is shipped with UNITY calibrated
to within .1dB. Each channel is calibrated by it’s respective UNITY ADJ on the back of the unit.
OUTPUT LEVEL - OPERATIONAL NOTE:
With program material being played, adjust the desired amount of PEAK REDUCTION and
LIMITER RESPONSE. Referring to the loudest peak in the program material, note how much
GAIN REDUCTION is occurring on the GR METER. Typical readings will be in the -3dB to
-7dB range. Adjust the OUTPUT LEVEL attenuator to have the inverse amount of gain. As an
example, if the GR METER is reading -5dB on the highest peaks adjust the OUTPUT ATTENU-
ATOR to +5dB. Go to a quiet passage of the program material. Using the IN/BYPASS switch,
you can now compare source and processed audio.
OUTPUT LEVEL - CALIBRATION PROCEDURE:
• Set PEAK REDUCTION & LIMITER RESPONSE fully-counterclockwise.
• Set OUTPUT LEVEL, LIMITER FEEDBACK & STEREO LEVEL RIDE to UNITY.
• Inject a +10dB 1-kHz tone. Verify using an external DMM or suitable meter.
• Switch between IN and BYPASS. External meter should read the same or within .1dB
• If not, adjust the UNITY trimmer (rear panel) until IN reads the same as BYPASS
T H E L 2 M M K I I I M / S V E R S I O N
R e q u i s i t e A u d i o E n g i n e e r i n g
L 2 M M k I I I
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