Echo

[BigEasy504]

I have a situation. I have the main outs and the control room outs of my TASCAM DM3200 going into my Mackie Big Knob input source select 2-Track A and 2-Track B and I have my Berlinger head phones amp going into the back of the MBK Headphone AMP jacks. I can hear everything fine but when MIC check I hear a delay or a slight echo in the headphones. Now I don't hear it in (PT10) the recording only when I'm doing a MIC Check or just talking into the MIC. Is there something in my DM3200 that I have inadvertently have set or something that needs to be set. Can someone offer some advisement please