Get Stoned

Another thought...

Try this: take the belt off the motor so that the platter won't move, lower the stylus onto the platter, switch on you amp and turn up the volume. Now switch on the motor and you should hear hum.

The hum will come and go as you switch on and off the motor. The hum isn't electrical, it is from the vibration of the motor transmitted through the table and shooting back up to the platter from the cone feet.

Try the above with footers under the SDS and then not. If you hear less hum when the footers are on, then the SDS and Power cable are acting as a vibration sink for the motor.

I think Philb's idea is worth considering, but I suspect that there would not be any differences in speed detected. If the VPI SDS was that supscetible to mechanical energy the product couldn't do what it does so well. I measured my speed using ISpectrum, a software based Oscilloscope, and a 1000 Hz test tone. The speed was rock stable.

I had a theory, but it's a stretch...

All the VPI motors vibrate considerably, if by chance Stringgreen's powercable from the SDS was pulling some of that vibrational energy away from the VPI motor, though the cable, and down though the SDS and footers into a vibrational sink. The net effect would be a motor that is vibrating less. Less vibration would yield a lower noise floor.

Stringgreen, can you post a photo of your setup?