[Navy I.C.]

instead of using a ground distr. block, 1. try using separate grounds for each grounded componet and 2. try to make sure the grounds are clean to the metal (sand a little if you have to) if that don't work double check that all of your power runs are not close enough to induce noise into your signal runs, but you said the noise don't increase with the volume so I would think its after the signal run...