Valentine 1 radar detector wiring

[iXXion]

I'm looking to plumb my earplug into a V1.  Valentine wants a $50 bill for the adapter, which is ludicrous for my purposes, although to be fair it has other features than simply an audio jack.

I found one source on the net that gave pin 4 of the RJ-11 jack as the audio source, but didn't indicate which would be ground.  Unlike other things, I'm loath to poke around my V1 with conductive materials like test leads due to the frequent admonition from folks who might know (meaning they have websites with freaky looking electrical diagrams) that incorrect connections can cause some internal and potentially expensive strife for the V1.  

Anybody got any helpful info?