Greetings Nick: You should be able to get good results with your technique. (You're essentially doing a poor-man's Direct Digital Sythesis, when reading a pre-constructed table like you are doing) Another way to do this is generate a sine wave, using one of the sine generator vi's and then run it through a series of comparators (use comparison primitive) each with a different threshold. Add the values of each comparator output, and voila, this is your stepped wave. In this manner, you are simulating a "flash" A/D convertor. Another way to do this, is to run a square wave generator (say at 400Hz) and MULTIPLY this by a sine wave at 50 Hz. This will give you a Sine wave modulated square wave, (or vice versa, since mathematically, they are identical!)
Eric