I would first try bypassing the voter and hook the link receiver directly to the 850 to make sure levels are good. There should be no reason you have low audio out of the controller the 850 normally has gobs of audio and has to be knocked down with a resistor of considerable ohmage in order not to overdrive a transmitter.
As someone else stated the oscilloscope is your friend here. Note the levels on the input and output of the controller with the scope when it is working properly then put the voter back in and compare. tom
