Cgs synth

I just finished the synthacon filter and I get a loud hum at the
output. The noise can be filtered and resonance can be applied to
it. Its not really noise, but a low E.

If I attach an audio source to the BP and HP inputs, I can hear the
audio as well. I dont hear audio when I plug it into the LP. The hum
may just be drowning it out (but I dont think its there).

Any ideas on what could be causing it?

Thanks
Scott