Lexicon MPX G2, Service Manual

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Lexicon
4-5
5. Set the Analyzer back to measure level.
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.
Frequency Response Measurement:
1. Disable all Filters on the Distortion Analyzer.
2. Apply a 1kHz-sinewave signal at -15.5dBu (130 mVRMS).
3. Set the Analyzer for a 0dB reference.
4. 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
5. Set the Low Gain to -25 using the front panel knob.
6. Verify the output level readings for each of the frequency settings in the table below.
Freq. Upper Lower
Hz (Vrms) dBu (Vrms) dBu
20,000 (1.1) 3.40 (.90) 1.28
16,000 (1.1) 3.39 (.90) 1.27
12,000 (1.1) 3.38 (.90) 1.26
10,000 (1.1) 3.37 (.90) 1.25
4,000 (1.1) 3.16 (.90) 1.04
2,000 (1.0) 2.51 (.81) 0.39
997 (.83) 0.62 (.65) -1.50
250 (.34) -7.07 (.27) -9.19
100 (.22) -10.79 (.17) -12.91
60 (.20) -11.59 (.16) -13.71
20 (.20) -12.05 (.15) -14.17
7. Set the Low Gain to +25 using the front panel knob.
8. Verify the output level readings for each of the frequency settings in the table below.
Freq. Upper Lower
Hz (Vrms) dBu (Vrms) dBu
20,000 (1.1) 3.41 (.90) 1.29
16,000 (1.1) 3.42 (.90) 1.30
12,000 (1.1) 3.43 (.90) 1.31
10,000 (1.1) 3.45 (.90) 1.33
4,000 (1.2) 3.64 (.92) 1.52
2,000 (1.3) 4.27 (1.0) 2.15
997 (1.6) 6.10 (1.2) 3.98
250 (3.8) 13.79 (3.0) 11.67
100 (5.8) 17.51 (4.6) 15.39
60 (6.4) 18.37 (5.0) 16.25
20 (6.8) 18.87 (5.4) 16.75