This is the traditional audio preamp configuration with the National Semiconductor LM382. The circuit has good gain and can be used with magnetic pickups or from signals from an auxiliary input.
This circuit is from Motorola documentation on 1976 power devices. SCRs are powered according to...
Assembled with SMD components this spy can be made very small. We found it in an Australian...
We found this circuit in an old documentation. The operational amplifier of the time can be...