Hi All,

I have been having trouble recording any surface waves lately.  I used =
the instrument several years ago and had no problem but now I do not =
seem to get low frequency.   I am using the PSN schematic for the =
preamp, filter and final stages.  There is both an unfiltered quake and =
an FFT posted at http://mit.midco.net/rpratt/  I noted the high =
frequency side of 2 peaks seems to have hard cutoff on this quake but =
have not noticed this before.  Where should I look to trouble shoot?  My =
suspicion is the electrolytic cap coupling to the final.








Hi All,
 
I have been having trouble recording =
any surface=20
waves lately.  I used the instrument several years ago and had =
no=20
problem but now I do not seem to get low frequency.   I am =
using the=20
PSN schematic for the preamp, filter and final stages.  There is =
both an=20
unfiltered quake and an FFT posted at http://mit.midco.net/rpratt/&nb=
sp; I=20
noted the high frequency side of 2 peaks seems to have hard cutoff on =
this quake=20
but have not noticed this before.  Where should I look to trouble=20
shoot?  My suspicion is the electrolytic cap coupling to the=20
final.
 
Randy