Wierd MIDI "noises" from a controller

Hi guys,

I bought an old Macie MCU (the darker one).

Connected to my M-Audio Fast Track Pro via MIDI I/O.

And now starts the wierd part - I can actually hear the MIDI commands through my speakers.

It's kind of a high-pitched screech that changes every time a different command is happening, for example - I move a fader, so it has to send a command to my daw - a new sound. same goes if a fader moves by automation. The only reason I figured out it's related to the MCU was because every time I put a track on Solo, all the other tracks are muted and the Mute button in the MCU's different tracks blink, and the sound I hear changes to the ryhthem of the blink. It's really annoying because it never stops - even while I'm playing something back.

Wierdest thing for me is that the sounds are still there when the MCU is not synched - when Protools is off and the MCU's on, it still makes these annoying sounds. It doesn't change though, unless I move a fader and then it gets annoyed, does a little sound and moves the fader back to it's place again.

And another strange thing, the noise is in a constant volume - the output knob on my interface doesn't affect the volume of the noise.

These sounds disappear if I shut the MCU off, though.

Anyway, anyone's experienecd anything like it before? know how to solve it?

My initial idea was (and still is) to buy a MIDI\USB adapter, to separate the MIDI commands from my audio interface and thus (hopefully) eliminating the problem. is it the right way to go?

Thanks!

Wierd MIDI "noises" from a controller