My original design had the PIC ground and the analog ground connected 
together.  THEN I read the specification for the player and it says 
"Analog return - Signal, never to be grounded inside attached device."  
I do not have access to the internals of the device only the interface 
specification but since it is a battery powered device I assume (and 
that is usually dangerous) that the Analog return is set to a bias point 
above DGnd and the audio signal is +/- the return potential. 

It's beginning to look like a unity gain differential OP-Amp is in my 
future.  Man I hate the addition cost and board area but it may be the 
only solution.

Phil

Gerhard Fiedler wrote:

>Phil Keller wrote:
>
>  
>
>>The peak detector is what I described, without knowing what it was
>>called.  It is sufficient for what I need.  (This is not precision, just
>>an indication of relative volume level.)  My problem is before that.  I
>>need to be able to translate an audio signal that is referenced to audio
>>ground to a signal with its reference to digital ground without
>>connecting the grounds together.
>>    
>>
>
>Why do you not want to (or why can't you) connect e.g. a PIC's ground to
>the analog reference ground? Depending on what you want to achieve, the
>ways to do it will be different.
>
>Gerhard
>  
>

-- 
===========================================
PK Consulting
Phil Keller
Fremont, Ca

Phil@PKConsulting.net



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