Echo circuit for Dynamic Microphones

[HighAmp]

Hiii
I need nice echo circuit without Distortion
special for '' Dynamic Microphones ''
i build circuit with pt2399 from datasheet
but it's very very bad
it's like '' helicopter voice '' hhhhh
how can I change in circuit for mic
thank you........

[djoffe]

The issue is there's not enough output from the dynamic mic. Best way is to have an external preamp...but, maybe you could get enough gain with a few value changes...It's hard to say exactly, because the data sheet is pretty sketchy...Here's a quick way to get 26 dB more gain...that should help SNR...if it works, maybe we can push the technique a bit farther...

We've changed a few caps and resistor values. R4 and R5 represent the revery path. Main change is the two caps, and R1, which probably was 10K-15K previously. You may want to bump up C1 a bit to move the low end roll-off down, but I wouldn't bother to start.

See enclosed file...LT1001 is just a placeholder for components on pins 15 and 16.