I'm using PT2399 IC for my echo circuit as shown in the application circuit. The circuit is working fine alone. But I'm using a mixer to feed the input. I'm using my yamaha mixer's auxillary output to feed the input of echo circuit and the output of echo circuit is fed to another channel (say echo channel), the mic is plugged into another channel of the mixer. When the fader of the echo channel is increased, the clarity of the mic output is decreasing and the sound gets dampened. It sounds as if the bass is decreasing and the sound is getting flat. I don't understand what the problem is. Please help me.