Feedback when using simple bypass switch, with booster pedal in amps FX loop

[Leeroy]

hi,

i managed to build myself a true bypass box using information i found on this site, so that I could bypass my multi FX pedal.  I run my guitar straight into the bypass box, which is connected to my multi fx, and i output straight into the input on my amp.  All works well untill I add my behringer pre-amp booster pedal into the FX loop of my amp.  Although i get no problems when running my amp on the clean channel, when i switch over to the distortion channel i get mega feedback (even when the booster pedal is not activated).  The feedback stops when i disconnect the leads from my amps FX loop.  Cean anyone tell me what the hck is goin on?!!!

Thanks

Lee

[petemoore]

 managed to build myself a true bypass box using information i found on this site, so that I could bypass my multi FX pedal.  I run my guitar straight into the bypass box, which is connected to my multi fx, and i output straight into the input on my amp.  All works well untill I add my behringer pre-amp booster pedal into the FX loop of my amp.  Although i get no problems when running my amp on the clean channel, when i switch over to the distortion channel i get mega feedback (even when the booster pedal is not activated).  The feedback stops when i disconnect the leads from my amps FX loop. 
  The pre-amp in the FX loop isn't true bypass, has buffers I think, but I don't know why this should cause problems either, have you tried a patch cord in the FX loop jacks to test if the loop works when straight pattched?