I am looking for some kind of device that will allow me add echo effects, to my performences. I am looking for a device that you can plub a microphone into, and when you talk, screem echos will be produced.

I found many Karaoke mixers and other sound processors, but the limit of the echo on them is moslty 1milly second. I need a device that will extand the echo to at least 2.5 ms.

Any suggestions?