From: jeedom74000@gmail.com   
      
   > The capacitance of your piezo stack is probably in the 10-nf range--it's   
   > worth measuring that, because R_out * C_piezo is probably the dominant   
   > pole in the loop right now.   
   >   
   > If you need any help with frequency-compensating the loop, ask.   
   > Cheers   
      
   Hmm, you've lost me there (that's how little I know about electronics!).   
   What do you mean by "probably the dominant pole in the loop right now"?   
   I have increased the capacitance on the output low pass and I can now increase   
   the gain without oscillating.   
   Now I have increased the output gain by "a lot" but somehow it does not seem   
   to improve much; I might be missing something   
      
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