Boss VF-1 Effect Processor

hello, 


 i need help to configure my Vf-1 to use with Marshall JCM900, what 
is the parameteres in the Global Menu - output, i have configured to 
LINE, but i try the others and the sound is very agressiv, my guitar 
is put in the front connector HI-Z Input is this correct....

  thanks for help me


 boss forever.....

 Bruno from POrtugal