Simple question as in subject: how can I create an echo effect in EE using sound capturing?

What I've created for now is:
1. I collect samples from microphone
2. In virtual Int set() in Echo sturct based on SoundCallback I rewrite ("=") the captured data to SoundCallback set() data ptr parameter. 3. I play the Echo object.

And what I get is really an echo but with some kind of squeak.

Is this the correct method of doing such thing?