I have an '04 A4 with the Audi Symphony HU. Recently, I had my local car stereo shop hook up an Alpine T-757 amp to drive an Alpine Type R 12" sub. I noticed that they used a line level converter from either the rear speakers or original sub in the rear deck to get the signal to the amp as it does not accept high level inputs. I won't say it sounds like crap, but it doesn't sound nearly as good as it did in my last car (POS Pontiac grand prix)- same sub/amp combo. Part of the problem may be the wires from the amp to the sub which they only used 14 gauge. Another reason may be the dynamics of the car itself as the Audi is built like a tank comparatively. In the Pontiac, that one sub about pounded my chest into cardiac arrest. It sounds just as loud in the Audi, but I barely feel it and it does not have the same quality, detailed sound. The power is fine and the settings on the amp are fine. So, before I ramble on even further, my question is does anyone know if the line level converter is possibly reducing the quality of the signal to the amp? Also, does the Symphony HU have a low level output that can be tapped into directly instead of having to use the line converter? Any help is greatly appreciated!