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AD2128 problem with audio breaking through open switches

Question asked by BigtimP on Jan 12, 2014
Latest reply on Jan 21, 2014 by BigtimP

Hello,  I wonder if anyone can help.

 

I am currently prototyping an audio routing device that must be capable of routing instrument and line level signals.

 

Based on some research I recently purchased the EVAL-AD2128EBZ board.

 

For my first test, I connected a headphone level audio signal to one of the inputs, and programmed the device to route this to one of the outputs.  I then recorded the output and controlled the switch to turn the routing on and off.

 

All this worked well at low signal levels (lower than line level based on the signal coming into my recorder)

 

However with the switch open,  if I increase the signal level to what I believe to be around line level, then the audio starts to break through the open switch and appear at the output.

 

I have the eval board in its default configuration, with the control supply provided by the USB connection to the PC. and Vdd at +8V.  I have link 4 in position A (but no -ve voltage applied to Vss)

 

Can anyone help.  Should I move Link 4 to position B OR apply +7V to Vdd and -7V to Vss, or in fact is this the wrong chip for the job?

 

Thank you in advance

 

Tim

 

ps audio clip attached of the signal breaking through the open switch

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