Lexicon MPX G2, Service Manual

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MPX G2 Service Manual
4-8
5. Verify the output level reading is between 1.06 to -1.56 dBu (875 to 647 mVRMS) at the following
frequency settings.
20,000Hz 16,000Hz 12,000Hz 10,000Hz
4,000Hz 2,000Hz 250Hz 100Hz
60Hz 20Hz
6. Turn the knob CCW to place the GTone circuit back into Byp 0.
THD+N Measurement:
1. Set the Analyzer to measure THD+N.
2. Enable the Lo pass filters on the analyzer (30kHz or 20kHz).
3. Verify an output THD+N reading is between (0.15 to 0.0007%) at the following frequency settings.
20,000Hz 15,000Hz 10,000Hz 5,000Hz
3,000Hz 997Hz 100Hz 20Hz
4. Set the Analyzer back to measure level.
THD+N Measurement with Soft Sat On:
1. Press the No button until the display reads: System Select Development. Turn the knob CCW until the
display reads: System Select Audio.
2. Press the Yes button once. The display reads: Audio Soft Sat Off. Turn the knob CW to turn the Soft
Sat circuit On.
3. Verify the output level readings for each of the input level settings in the table below.
Levels Upper Lower
(Vrms) % %
-3dBu (.55) 1.10 0.14
-2dBu (.60) 3.06 0.73
-1dBu (.70) 5.38 1.66
0dBu (.80) 7.54 2.60
+1dBu (.90) 9.38 3.42
5. Turn the knob CCW to turn the Soft Sat circuit back Off.
Signal To Noise Ratio:
1. Apply a 1kHz-sinewave signal at +2.2dBu (1.0 Vrms).
2. Set the Analyzer for a 0dB reference (@ 1kHz).
3. Turn off the oscillator.
4. Verify an output level reading between -99.94 to-120.00 dBu (7.8 to 0.8 uVRMS).
5. Turn the oscillator back on.
Input To Send Test with Dynamic Gain On:
This test will verify the Audio signal path from the Rear Input to the Send output of the MPX G2
with the Dynamic Gain circuit enabled. You will now need to set the following parameters for the following
tests
Setup:
1. Press the No Button once. The display reads: System Select Audio.
2. Turn the Knob CW until the display reads: System Select Development.