Audio;sound feedback from capture inputs

[mrlewp]

When trying to capture VHS thru TV composite inputs attached to VCR, the sound wildly echoes and goes thru the roof in volume if I dont quickly set vol. slider to 0 .
This happened way back , and I figured it out. Now I've tried everything I know, and would have known back then...but cant stop it.
It only happens currently when I try to capture VHS tape to movie file using Pinnacle Studio 9.
Oddly, I can hear the VHS source fine with Studio's input sliders set to "0", but if I try to raise the level so that signal appears, then echo begins, leading to insane volume.
When I finish making captured file, there is no sound with the file playback, so I'm thinking those input sliders need to be adjusted up.....but thus the problem occurs.
There IS NO sound output from PC to VCR to create a loop !!??