[rfeenstra]

Interestingly, I set my 70 (unmodified) next to the 570 and fed it the same signal.  Aside from the typical 70 issues, it has a better high frequency response. So, now I'm going to do some audio testing on the 570 to see if the audio amp section is rolling off the highs.  Or maybe my Celestion speaker cone is not so good!  I may have to swap speakers to see what that does.  Also, maybe I'll change that 220 pf cap to a 100 pf in the detector circuit.  Lots of stuff to play with.... fun!