Basic oscillator

Hi,
I have set up a really simple oscillator (don't know wave shape).
I used a little amplifier board I got from maplin, it has a microphone and a
speaker. When I put the mic near the speaker it oscillates.


My questions are, how do I make the amplifier oscillate without the speaker
and mic ? I don't want to hear that horrible squelch ever again . What
components do I need? I'm looking for the simplest possible solution. Also
is the output a of my speaker-mic circuit a sinewave or a squarewave(or
something else?) ?


Thanks,

wydaq

An amplifier is designed to amplify NOT oscillate. You are making it oscillate with acoustic feedback - something it was not designed to do.

If you want an oscillator, then use an oscillator circuit.

oscillator circuits

To obtain a square wave (not quite) use an LM555 or NE555. For a sine wave, a hartley or colpitts circuit can be used. Do a Google search for these for more information. The acoustic feedback could produce a sine wave if the amplitude was controlled, but since it is not controlled it is probably more like a square wave.