Rap 'n Tap
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From: Ben H. Tongue
Date: 11/12/00
Time: 1:38:49 PM
Remote Name: 209.236.135.19
Darryl,
Wiring the two earphone elements in parallel results in a 300 Ohm device, in parallel, a 1,200 Ohm device. One is as sensitive as the other if properly impedance matched. The approach you use should depend upon the impedance ratings of any transformer you have available. You will just need four times as much transformation ratio with the 300 Ohm connection than you will with the 1,200 Ohm connection. I suggest that you read Article #5 at http://uweb.superlink.net/bhtongue for further info on this wubject.
The transformed impedance with which to load your detector is probably between 50k and 150k Ohms. I suggest that you first try one Calrad #45-700 transformer and connect the phone elements in series.
Ben