Hi, I am designing a signal tracer based on the frontend of a Heathkit IT-5383, using an LM386 as the power amplifier, with a gain of approximately 500 and an input impedance of 500 kΩ. I would like to add the noise function found in the Heathkit IT-12.
To achieve this, I plan to add a secondary winding on a transformer that provides 120 V, rectify this voltage with a diode and a 22 µF capacitor, and then include an RC filter consisting of a 10 kΩ resistor and a 47 µF capacitor. The output of this circuit would be connected to the probe through a 68 kΩ resistor, similar to how it works in the IT-12.
My question is: will the gain of the device be sufficient or excessive for this function? Do you have any other ideas on how to implement it? I am open to suggestions.