Ajustement du DAC

Citation : Noise is the result of improperly trimmed DAC (digital / analog converter).

• Open the top cover of JD-990.
• With the JD turned off, hold down INC + DEC buttons then turn power on.
• This should get you into the test mode.
• Then press UTILITY + F3. This gets you into the MSB Adjustment page.
• Make sure the volume control is at maximum. (Watch out you speakers!)
• Press the value knob, a 440hz sine-wave is produced.
• Use an instrument such as an oscilloscope to observe the output waveform. If you don’t have oscilloscope, you can use headphones and listen carefully with your ears.
• Adjust VR1 to obtain a smooth sine wave.
• The VR1 is located on the main board, top right side of it (if JD is placed with its front side facing you). In fact it is the only trimmer potentiometer there.