external audio input module

[johns at oei.com]

     I remember countless hours spent trying to characterize non-electronic 
     real-world audio waveforms.  I too concluded that most signals will 
     average about 1 Vpp.  But what was really difficult was characterizing 
     the exceptions.  
     
     Microphones and especially guitars can give some really tiny and 
     really large signals (read that: large dynamic range).  Of the 
     electronic instruments I tested, I found that the dynamic range was 
     somewhat limited and tamed probably because of the output stage that 
     has a max output voltage.  Their outputs were more predictable and, 
     hence, easier to process externally.
     
     So I would like to offer my 2 cents about your circuit.  I would think 
     about putting some kind of dynamic (or maybe hard) limiter on the 
     input or output because, if you are processing audio through an 
     amplifier with more gain than you need (just in case), you will 
     probably drive the signal way beyond the clipping threshold of the 
     amplifier.
     
     John Speth - johns at oei.com