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I am looking at the voltage across the speakers V(Speaker1) - V(Speaker2). I expected the attached circuit to oscillate at periodic frequency, with the switch closed.

The simulator version does not work, even though the real physical circuit works! The speaker hums, and on the oscilloscope shows a periodic spike across the speakers.

Appreciate any help in figuring out what the problem is with the simulator. Thanks!

No idea how the transformers are simulated here, but here is an overly simplified version, that works, before the speaker starts to shunt the inductor. The magnetic coupling is not accounted for, so in order to have an idea how the active resistance of the speaker affects the generator, the resistors R4 and R3 were added (Rspeaker x Turns ratio). Best generation is achieved when R3 and R4 are infinity, but that can not be the case if you want an actual output from the speaker.

@kams,

Your transformer ratio may be set inappropriately.

Try setting the transformer turns ratio to:

1/100

For help on this, you might also like to have a look at:

https://www.circuitlab.com/circuit/vehv3p/understanding-the-cl-transformer-symbol-01/

and

https://www.circuitlab.com/circuit/53mvn2/coupled-inductors-01-transformer-comparison-03/

Your circuit may start up faster if you either put this expression into V1:

3*(1-exp(-T/10u))

or replace the switch with the time controlled switch set to close at say, T=1ps.

For the why of this, search CL for:

initial conditions

or:

startup

:)

Excellent suggestions! Thanks!