Hi folks. Here is the schematic I am using to build the solid state stereo decoder using the lm1800 IC. It shows the input running through a 2uF electrolytic











I am planning on picking up the input where the "MPX output" is shown here on the telefunken schematic. Does this sound reasonable?










Now here is where the left and right output of the lm1800 circuit will attach. (Where is says MPX Input on the telefunken schematic) My question at this point is why are there 68K resisters at the MPX Input? Does that have something to do with the tube version of the MPX decoder? Could I bypass the resisters and connect directly into the tape input socket at 3 and 5?

Don't bypass anything.
Connect it as it's supposed to be.

Concerning the MPX decoder the older tube radios sometimes used a higher level signal on the MPX out jack which may overload the solid state MPX decoder. If you hear distortion you will have to increase the size of the 10K resistor somewhat untill the distortion is gone or simply install a 100k multi turn trimmer pot to provide for an accurate adjustment of the input signal to the MPX decoder.