Mine works great with one small exception. One of the voices is sometimes off, meaning that every fourth note played sounds several steps sharp.
This happens every once in a while and then the problem goes away by itself.
When it is not having that problem everything seems to be A-OK. I love the ring modulation and I also love the sliders for the LFO which allow me to easily select what I want to modulate.
I used the CS-50 (as well as the Big Briar Etherwave theremin) when I played with The Analog Synthesizer Ensemble in 2007: http://www.halmcgee.com/Music/theanalog ... e2007.html