Earlier I made this filter to convert a square wave to a pretty good looking AC sine wave:

The waveform looked great when it was all on the breadboard, but for some reason after soldering it onto perfboard the resulting waveform looks quite noisy (better visible on the oscilloscope):

Now I wonder: Is this because I chose such high resistor values (15k's) for the filter? I will test this.

Eh, maybe another time.