Thanks for looking! I have a Hartke "Kickback 15 combo" I just purchased and it does not have an "Aux send -return" ...I would like to run my rackmount "TPS II tube preamp" through it and or my "T.C Electronic" processor. Because these are line level signals (I've heard) and not instrument signals is there a problem chaining them together or just using one plugged into the amps single imput?? Say's nothing in the amps manual about this. My old combo I used the Aux -send so now not sure what to do.........Basicaly it would be ...Bass 2 preamp 2 processor 2 amp imput.................Thanks for your time!!