Adjustable phase shift/delay??

[eromlignod]

Guys:

I'm an ME designing an application that reads an audio signal
(microphone). I would like to slightly delay, or shift the signal
backwards--it needs to be adjustable (with a knob).

Is there an easy way to do this? Is there an audio chip/circuit
already made to do this for you, or perhaps a simple op amp circuit?

Thanks for all replies!

Don