Doepfer

speaking of res loops (rs120)..
i was playing around w the res loop on an AS rs110 last night 
when suddenly a patch i made caused the audio to go away and 
not come back by undoing the patch.  i patched an a140 output to 
the resonance loop's input (nothing connected to res loop's 
output.)  and 'blip', out goes the signal.  i thought i had a bad 
cable or jack, traced the signal problem to the filter, it had 
stopped passing audio, was 'locked up'.  that is, until i wiggled 
the freq knob on the rs110, then the sound came back w a 
screech.  i assume the filter went into self-oscillation at an 
inaudible freq when i plugged in the a140.  anybody know if is 
this harmful?  either way, anybody know more about possibly 
harmful patches?  
i'm generally a plug-anything-to-anything experimentor but this 
has me wondering if it's possible to abuse a circuit to death.  
-duff