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DC Blocking Element Appears to Introduce DC Offset

Question asked by db10 on Jul 4, 2014
Latest reply on Jul 8, 2014 by db10

I have a DC blocking element in a signal flow. Further "downstream" is an RMS level detector with a readback element. It was observed that prior to the application of an audio signal to the signal path that the level detector reads back 0x00 0x00 0x00 0x01 or essentially no signal. After connecting an audio source the the same path the level detector became active. Upon removal of the source it was discovered that a residual value at the level detector remained in the range of -47 dB.  If the test is repeated with the DC Blocking element removed, the read back element is seen to decay to near zero again.

 

So it appears that the DC block, is introducing a small DC error. Note that not only does this show up in the read back element but also introduces a real measurable output at an output DAC.

 

Is this to be expected?

 

 

 


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