Two Thors Driving One Motor

I have two Thor Spin Controllers to drive one MagMotor s28-400.
(actually two thors on left side and two on right side driving weapon GB mtrs) I am getting what sounds like a lot of electric HUM out of the system when is runs (have not run it at full speed). The noise is not mechanical- the spin down is basically silent.

The setup is IFI 900Mhz Issac 16 recvr with two PWM channels outputting
the same PWM signals (value) to the pair of thor spin controllers,
and the thor spin controllers are wired exactly like the IFI drawing,
(including the update since the drawing was incorrect a while back).
This is for each side of the robot. Is it ok to drive one motor with two thor spin controllers and not get any weird effects that will effect operation or performance? It seems to operate correctly, but any suggestions for improvements would be very much appreciated.

**The hum you are hearing is most likely the 120Hz output chop frequency. If your MagMotor has 2 separate winding and you do not over-current the Thors, this should not be a problem.

If the Motor has only one winding, so that you have both Thors connected to the same winding, this may work - but there is no way to guarantee the current between the 2 Thor will be shared equally. This is because you can not synchronize that the chop “ON�? time for each Thor is occurring at the same time even with the same input signal. To help with the synchronizing, you should run the 2 Thors from 1 PWM output and use a “Y�? cable.**