just installed a sony CDX-GT 510 into my 87 audi quattro 5000cs turbo. The rear speakers are amplified and i wanted to keep the stock amp so i purchased a PAC OEM 2 from crutchfield in order to make it work. Its working great and sounds good, but theres one problem. With the radio on the rear speakers work, along with the front, as it should, but when i put in a cd there is no sound coming from the rear speakers, only the front ones. I am not sure why this is happening, but does anyone have a solution or can tell me why the rear speakers don't work with a cd.
Why on earth would you want to keep the stock amp, it's garbage. Rewire the rears to the HU.
The reason the rears don't work on radio and not on CD is because you've wired the remote on for the amp to the power antenna feed on the Sony HU. Some HU's cut the power antenna feed when you switch from radio to CD so that if you have an electric aerial it will retract unless needed.
Rewire the remote on for the amp to the "remote on" on the Sony