Preamp Distortion Test - Roland VS-2480 Tech Support Help Site

Preamp Distortion Test

NOTE: All these steps CAN be completed WITHOUT listening to anything. TURN YOUR SPEAKERS AND 'PHONES OFF, or WAY WAY DOWN.

1) Go to the GEN/OSC screen. Select a 1KHz Sine Wave as the "SOURCE". Turn the MIX button OFF. Turn on Direct Out 6. Turn the OSC. ON.

2) Go to the EZRouting screen. Connect your analog output 6 to Direct Buss 6. You should now have a nice 1KHz sine wave emanating from analog output #6. You can verify this by connecting to any external amp (KEEP THE VOLUME DOWN!!).

3) Turn ALL the SENS knobs MAX CCW (counter clock wise), and place ALL the PADs IN. Connect a 1/4" cable between output #6 and the input to be tested.

4) Invoke the Analyzer, and set it to monitor the INPUT UNDER TEST.

5) SLOWLY rotate the SENS control, while monitoring the Level on the left side of the Analyzer display. You should see a SINGLE VERTICAL BAR @ 1KHz in the main portion of the Analyzer display.

6) As you continue to raise the input control, the 1KHz bar will grow, and smaller sidebars will start at 800Hz and 1.2KHz. This is Normal.

i.e. this is good:

7) When the input overloads, all kinds of Upper Harmonics will be displayed. If this occurs at 0dB on the input meter, that's cool. If it occurs at -4 or -6 dB on the input Meter, you need the fix.

i.e. this is bad:

Keep in mind, once you overdrive the input, you might not notice the distortion on that channel for awhile. That's the quick theory behind the "Crank".

Text by: Lakestone Karl
Graphics by: Falcon Eddy

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