The Fender Hot Rod is not really suitable for 4CM because, as gtrdude 72 said, you lose your tone shaping and volume control. Also, the power amp volume is wide open and VERY loud when you turn off the FX Loop block . You could insert a helix preamp and toggle it on and off with the loop ( preamp on, loop off and vice versa), but turn the volume down (on the helix preamp) first or you might get a very loud shock.