Mailist to discuss all issues regarding the Digitech GSP-2101 Guitar FX Processor

Hi together,
I have a problem with my Digitech 2101. I want to use a Kitty Hawk 
Quattro Tube Preamp as FX Loop Preamp in the Digitech. The Kitty Hawk 
have only 1 Input and 1 Mono Output, no FX Send / Return.
I go with the Guitar into the Input of  the 2101 and connect Fx Send 
to Input of the Kitty Hawk. With the output of the Kiity I go to Fx 
return of the 2101. The Problem is, that the Signal of the Kitty 
comes out very flat , not good at all.
Have anyone an idea what the problem is, or any better Idea to 
connect the Amps ?
Maybe I have to change some settings in the Digitech ?

Thanks for your help.
Steve