There's now easy way to catch the signals. But here's how I'll do it.
1) use your Tesla account to log in here:
Service and diagnostic information for independent businesses and individuals involved in the professional maintenance and repair of Tesla vehicles.
2) in the service section, select the picture of your vehicle (for demonstration purpose, I'll use my 2016 Model X).
3) You'll end up here (
Service and diagnostic information for independent businesses and individuals involved in the professional maintenance and repair of Tesla vehicles.) where you can select the one of your build. Mine is
2015-2020 Model X Circuit & Connector Reference
4) Now you need to search for the right build (mine is LHD SOP 2a) where you can find the Circuit Diagram and Connector Reference.
5) At the
Circuit Diagram on page 4, you can find the MCU and it's connector names (note AU00 = base audio and AU01 = premium audio).
6) Relevant connectors are X174 and X175
7) Also note down the pin numbers for the individual audio channels
8) Now go back to the page as per 4) above and open the
Connector Reference
9) Search for X174 and X175 on the left side of the webpage and click on it.
10) On the opening page, you can see the connector location, the connector type (manufacturer and product-id) as well as the connector's pin assignment with wire thickness and wire color (also compare the color with the circuit diagram)
11) search the Internet for that connector and for its mating connector. When you order both connector types (male and female), you can now simply build a small extension, e.g. 4’ long, from which you can tap the audio signals coming out of the MCU and route them to the amplifier. If you don't want to run new, thicker audio cables, you can feed the amplified signals back into the original wiring harness via the other side of the extension. Other cables that do not transmit audio signals are simply looped through the extension (e.g. earthing cables).
In this way, the original Tesla wiring harness is kept in its original condition.