ya...The DAQ supply is separate from other supply..AH...i just notice...i always didnt connect the Vgnd to the DAQ (-)..May b that the reason i cant control the output Voltage..But also i try put a 1K sine wave to the audio input, the output didnt show any sine wave..where might have the sine wave gone to? i try to check every pin but other than pin 6..i cant find any sine wave..is it possible that 1k sine wave got filter away?