MPX 200
Service Manual
4-4
Setup
1.
Turn on the MPX 200 and wait for the Power On Diagnostics cycle to finish.
2. Set the MPX 200 for Analog in and out by pressing and holding the Bypass button until
SYS
flashes,
then release.
3. Press the Bypass button once. The display will read
Src.
4. Turn the Adjust knob and select
ana
to set the unit for a Analog input.
5. Press and hold the Bypass until it goes back into normal operating mode.
6. Turn the Program Select Knob to Program #1.
7. Press the Bypass button on the front panel and verify that the Bypass button LED lights, and the display
flashes
bYP
.
8. Connect unbalanced audio cables between the Low Distortion Oscillator and the MPX 200 Left and
Right Inputs.
9. Connect an unbalanced audio cable between the MPX 200 Left output and the Distortion Analyzer.
10. Set the Distortion Analyzer to measure VRMS.
11. Turn the Input Trim knob fully clockwise.
Analog In To Analog Out Audio Test
1. Apply a 1kHz-sinewave signal to the MPX 200 Left and Right Inputs @ 775 mVRMS (0dBu).
2. Connect the Left Output to the Distortion Analyzer.
3. Adjust the Input knob for a level just below clipping.
4. Measure the Left Output for a level between 2.273 and 1.781 VRMS (9.35 and 7.23dBu).
5. Switch the cable from the Left Output to the Right Output and repeat the test.
Frequency Response
These tests will verify the frequency response specifications of the Left and Right analog inputs to the Left
and Right output signal paths of the MPX 200.
Analog In To Analog Out Frequency Response Test
1. Disable all Filters on the Distortion Analyzer
2. Apply a 1kHz-sinewave signal to the MPX 200 Left and Right Inputs @ 218 mVRMS (-11dBu).
3. Connect the Left Output to the Distortion Analyzer.
4. Set the Analyzer for a 0dB reference (@1kHz).
5. Sweep the Oscillator from 20Hz to 20kHz and verify the level stays /- 1.0dBr throughout the
sweep.
6. Switch the cable from the Left Output to the Right Output and repeat the test.
THD+N Measurement
These tests will verify the THD+N specifications of the MPX 200 Left and Right input to output circuitry.
Analog In To Analog Out THD+N Test
1. Apply a 1kHz-sinewave signal to the MPX 200 Left and Right Inputs @ 218 mVRMS (-11dBu).
2. Connect the Left Output to the Distortion Analyzer.
3. Set the Distortion Analyzer to measure THD.
4. Enable the Low pass filters on the Analyzer (30kHz, 20kHz).
5. Verify the Left output THD+Noise level on the Analyzer is <0.05%.
6. Switch the cable from the Left Output to the Right Output and repeat the test.
Crosstalk Test
Analog In To Analog Out Crosstalk Test
1. Apply a 1kHz-sinewave signal to the MPX 200 Left Input @ 218 mVRMS (-11dBu).
2. Insert an undriven phone plug in the Right Input.
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