guitar and amp issues?

[ClintBarton]

Hello,

i have a marshall jcm900 amplifier with recording compensation on the back and direct line out, when i play my guitar with usb direct to audacity its fine and a clear recording, but when i run it through my jcm stack i get a high pitched scream whilst recording ,you can still hear the guitar , , iv twiddled with everything trying to stop it but no joy,my other problem is the delay that comes with playing and recording? is there anyway to remove the delay?

Please help

I didn't find the right solution from the internet.

References:
https://forum.audacityteam.org/viewtopic.php?f=11&t=53482
digital production studio

Thank you

[blankslot]

VDSV

[blankshoot]

DGDB