Low level oscillation hum in Bass drivers..??

[JandG]

I have a low level oscillation in my Vifa m26wr 's ran by BASH 300S active plates. A 300B in PP runs a coat; fe103a variant for the wide range, & a ribbon @ 10,000hz with a 2uf cap..It anoys me more than antthing, system sound awsome, but the very low level oscillating hum is there the minute I switch on the BASH plates, they are set @ 13oHZ. I am running off my tube amps 8ohm taps to both the Corals & the BASH plates..I thought doing it this way was the best.. it sounds the best I do know that. but there must be something going wrong. I run a TVC & a modded DAC-AH for source, they are all fine.. ONLY when I turn on the BASH plates do I hear the hum, it is low & does't seam to change with volume.. just is there... what the heck...? should I switch to my 4ohm taps on tube amp..? I have ran it this way for months,, sonics are killer, but I gotta get rid off the Oscillation.