x10 v3 musicalfidelity

i have x10 v3 it work very well behind cd player but when i tried to put it between amp and preamp , it add so much noise did any one have this problem before , and on the back of unit it has tape loop output i do not known what can i use with tape loop output and some one please show me how to put it between amp and preamp with out noise or distortion , i have amp a3.2 and preamp a3.2 , thank you for all input
x10 is a feedback unit. adding an extra feedback on the any amplification path may result an instability of an operation in any component. however it will correct the stages where the feedback is not deep enough and will procces the responce more linear.