Yamaha CS-5 Trouble shooting.

[Cymatics]

Hi Everyone, this is my first post here. It's great to have a place to meet other Aussie synth heads! :)
Recently when using my CS-5 I notice this noise that happens whenever notes are played, for as long as the VCA is 'opened'. This happens even when the oscillators are turned down.
I've included a link to a clip to save trying to describe it.

http://soundclick.com/share?songid=8950197

- I've got the sustain and release knobs at 1 o'clock
- about 17 seconds in I open the filter so *WARNING* it gets louder.
- At 23 seconds I turned down the Oscillator volume, so you can hear the noise by itself. I then turn down the 'release' knob.
- the 'noise' knob is turned all the way down :wink:

Any idea what this could be, and if it's an easy fix?

Thanks in advance for any info.

[Thirteen]

Faulty VCA or VCA setup? Noise generator leakage from the mixer? Hard to tell without opening the machine and tracing which section it is originating at.