For a modern A/V receiver 'speaker out' to line level (say you're using Zone 2 out the back of your A/V receiver and wish to feed another amp that handles only outdoor speakers but you wish the outdoor amp volume to be controlled by A/V receiver) then:

 - R1 = 3.9K @ 1watt
 - R2 = 430ohm @ 1/2watt

and

 - R1 connects from Speaker out RIGHT+ to RIGHT/RCA+ 
 - R2 connects from Speaker out RIGHT- to RIGHT/RCA- *AND* RIGHT/RCA+(only at RCA)

Repeat for LEFT channel, R3 and R4.  -(negative) connections are shared both ends. 

Speaker to Line PCB, for home audio - NOT car audio:

[![Speaker to Line PCB][1]][1]


  [1]: https://i.sstatic.net/uWceq.jpg "Speaker to Line PCB"