Blitzsafe DSP1 DSP Adapter

Purchased this to install an aftermarket MP3 player in a '99 BMW 5-series with the factory DSP stereo system. This adapter works fine, however there is little to no filtering on the power input. The 5-series is notorious for having a 'noisy' electrical system, and this manifests as high-pitched whine when the CD player source is selected (this adapter connects to the CD player digital input). Installing a simple auto power filter may resolve the problem. Otherwise a compact, simple solution to a very annoying problem.