Elektor Formant Modular

hi. i have a formant that i'm slowly bringing back to life. i have 2
oscillators and they are working now ( though one of them is quite
unstable) I have got a bad case of bleed to the output from all the
waveforms even though they are switched off. so if i switch off all
the waveforms and connect a headphone to the osc out, i can still hear
the waveforms ( a lot lower though) could this have anything to do
with the power supply? it doesnt have a ground plug... ( not using the
original elektor psu) or maybe something else is wrong.. any suggestions?
thanks!