If you're a Nova user and have the original power supply (with the rubber shield around the connector), I think it's very much worth buying the revised version that they have now. It has a standard MIDI-style connector with a metal shield that holds much more securely.
My old PSU emitted quite a loud whine when the nova was turned off and a dull buzz when it was on. I always had zipper noise from expression pedal input and the audio ins were noisy. All those issues are gone now. The whole thing is cleaner, deeper, and more fun to play with!
What's even crazier is that I had major
crashing issues with Pro-Tools M-Powered with just a stereo track and one midi track for the nova that I couldn't figure out for the life of me. It wouldn't work for more than a minute of sequencing. Since the new PSU, I've had (so far) no such issues. I'm convinced the PSU on the Nova was blinking for an instant, sending some sort of spurious MIDI data that sent PT reeling. [shrug]... all I know is that the new PSU is all I changed and it works now!
I don't know if I had a bum unit for almost a decade and didn't realize it, but if you experience ANY of these symptoms, don't hesistate to spend ~$75 to enjoy the true beauty of this beast again!