Click noise

Hi all,
Just wondering if anyone has seen this before..

Setup is Nion Ne with 4x4 in / out card and three line out cards.

Design is under way, sound system operational but Nion design not totally completed .

Input design stage is in - HPF - 6 band parametric - compressor - mixer ..and on to the rest.

No settings in parametric " empty"..

Issue is a click sound at high frequency has been described as like a scratch on an old record ticking. This only happens when a signal arrives at the input and is more noticeable at the start of words or music. Almost like a noisy gate opening up.

By using CHIMP and the sniffer probe it was traced to the empty parametric. Deleting the  parametric modules ( one on each channel) fixed the issue. Using bypass in the parametric had no affect on the noise.

DSP shows about 74 % total with DSP A being 99% B 93% C has plenty left.

Anyone seen  anything like this ??

Thanks

Ray
NZ