Cross Contamination Explained.

The problem of noise cross contamination through power supply is often overlooked. Reducing its effect can result in significant performance gains for any system.

The key point is to understand is that each system component is not blameless and generates significant mains noise itself. In terms of power supply, it is also usually in close proximity to other components in the system, compounding the problem.

If you have system that contains a single component, one filter will protect it from mains borne noise:

Despite the presence of the filter, adding other components still allows noise to circulate in the system. Any noise generated within the system passes from one system component to another as they are all connected to each other in parallel after the filter. The presence of the filter will have an effect on this transmission, but it is far from the optimum solution.

A multiple filter configuration, as pioneered by ISOL-8's designer Nic Poulson, is the optimum solution. External noise is blocked as before. But significantly, each component is also prevented from influencing the performance of another, releasing maximum performance.