It's all in tuning the oscillators. Also, keep the quandrant knob centered, and keep the 2 attenuators back off from full clockwise. Also leave the 2 polarity switches in the center position. They are for removing the + or - from each channel, and using those can lead to more mangled tones. I assume you are taking the output from the RING out, so other than that, experiment with the tuning. Also try starting with sines. Its easier to hear and understand how the sum/difference work together when you have less overtones to begin with. Keep messing with it, because I find the uMod to be one of the cleaner sounding ones available. If you're stuck, I can try to come up with a patch for you later.