Hi,

thanks for the replies.  I've just done a search of the mail archive (which I should have done
fiirst!) and found:

> The 4.5 Hz is Mark Products L10B single vertical geophone in aluminum case
> with 2 3/4 inch spike,3 foot lead and Amphib IV connector.  They have a
> shunt resistor soldered across them for approximately 60% damping.

> The coil resistance for the 4.5 hz sensor is around 220 ohms.

So it looks like I just connect it straight to my amp.

cheers


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