Rick Groleau wrote:
 > John Popelish wrote:
 >> Rick Groleau wrote:
  >>>For anyone who's interested, I've just put together a page of my 
system,
(snip)
>>> http://users.rcn.com/rgroleau/seismo/index.html
(snip)
>> Mechanically, the design looks very nice.  Electronically, it is 
>> pretty primitive and simple upgrades could improve it significantly.
>> 
>> The coil is unshielded, and the amplifier has no filter function 
>> included to reject either 60 cycle hum or other mechanical noise that 
>> isn't part of the seismic signal.  Still it does pretty well with what 
>> it's got.
>> 
>> Are you interested in changing anything at this point?
> 
> Thanks for the comments, John. And yes, I wouldn't mind replacing the 
> amplifier with something more up-to-date, and with connecting the system 
> to my computer (which may be difficult, since I use a Mac). Any suggestions?

I am fascinated with the germanium amplifier and how it might be 
simply upgraded.  Are you interested in replacing a few components to 
get more gain and less noise from it before you replace it?  It is a 
museum piece.

If so, I would like to know what the collector voltage is with respect 
to ground for each stage.  I suspect that the choice of bias resistors 
is not at all optimum to get the full capability out of these old 
transistors.

The cheapest digitizer I know of to get something into your computer 
would be one of the DATAQ units available on this page:
http://www.dataq.com/products/startkit/index.htm

One of these could be hooked up between your present amplifier and the 
MAC.
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