The physical method you used to tap into the signal is just fine. Off the top of my head I don't know what 14 and 7 are, but I'll assume they are one channel of signal from radio to amp.

The problem you have is that you have a DIGITAL signal processing (DSP) unit. In these units the radio outputs a digital signal, not an analog one, to the amplifier. Any attempt to tap into this signal will be unsuccessful.

You basically have 2 courses to follow: tap into a signal after the amp and use JL Cleansweeps (or the like) to re-assemble the signal OR remove the DSP amplifier and have your radio revert back to analog. You'll lose DSP, but gain an analog output.

d-