yesterday i connected my amp up as usual at church... Musicman SUB->sansamp BDDI->Nemesis NC-210 ...turned the amp on, turned the sansamp on, turned up the bass volume, gain to 1 o'clock, then as i slowly turned up the master...SHRIEK!!! Shocked, i turned the amp immediately off, looked for any loose cables...but everything seemed fine - so i turned up the master again - this time no shriek - good - but then, as i clicked the sansamp on - SHRIEK!! Again! it sounds sorta like feedback but worse, building in volume and nothing quite like i've heard before...my guitarist said his effects loop sounded similar when it had problems - but i'm not using the FX loop i'm thinking it's the sansamp, but do pedals make that sound? it's very loud...what could it be? the amp works fine today for some reason, even with the sansamp, but i'm scared as to what it could be please help...!