oscillation

We've (@rpschultz) recently discovered that the buffer circuit we have in our upcoming tuner makes a nasty high pitch noise if the output is plugged into an amp and there's no input cable connected to an instrument/guitar. We're currently using the TL072 option (ignore the OPA1642 in the...

hey guys i,m new to this forum and Lt spice I am planning on building a FM bug using hardware, i am trying to simulate this circuit using LTspice In simulation i am replacing the microphone with a voltage source of 10mV and 2kHz then removing 68k resistor. simulation file is attched.Kindly...

I've built an AM tube transmitter. I don't have much experience in electronics. Can you please verify this circuit and tell me if it would work or how can I improve its performance? It uses an Armstrong oscillator to make the carrier frequency.