You can use the headphone jack to the Recorder.
The best way to do this is to use the diode output on the 600 right to the recorder. Here are the instructions for the R390 but its the same on the 600
http://www.r390a.com/html/diode_load.htmlThe last option is to use a speaker to line level converter. Available at any car audio retailer. This allows factory car stereo speaker leads to be converted to RCA low level to drive an amp. Newer models actualy work very well and these are cheap.
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