Strange tapping sound problem ?

Hope you guys can help,

When I plug my Nord lead A1 synth into my M-Audio soundcard all is well and good.

No noise, Cubase 9 works fine.

But when I plug a lead from My Micro Brute or Sledge 2 synth I get a really fast fluttering noise, like fast constant tapping very fast.

The noise is even there when the synths are turned off and only goes when I unplug leads from the outputs on the synths.

Ive tried different leads and like I say the Nord is fine !

Any ideas what is causing the fast tapping noise at like 32 taps a second or close ?

Thanks in advance

Don :slight_smile: