COR,
What make of computer and does it have on-board graphics?
If you can, look at the pulses out of the PP with an oscilloscope. I will bet you have ringing or even multiple spikes on the pulse. What i think happens is, the driver actually sees
two pulses in a hit or miss fashion, and thus it sounds like a mallet / hammer is hitting the stepper motor.
If you can, try adding a different video card. Some computers allow you to jumper the on
board graphics out. That "may" not cure it. Other then that, i don't believe you can do anything about it.
You can use a Smooth Stepper with that computer and not have any problems.
Just check out the pulse before you get into spending any money on anything.
( BTW, i USE GECKO DRIVES AND THEY WILL NOT CURE A SCREWED UP PULSE, NOR ANY SETTING IN WINDOWS THAT I AM AWARE OF )
RICH