Helpful information about VPI motor hum
I hope this post might be helpful to some of you out there. I have a scoutmaster turntable with a 300 RPM motor and SDS speed controller. I have had some low-level hum coming from the motor. I could initially hear this coming from the speakers. I tried a mouse pad under the motor and this helped. So I opted to get a custom made Terrastone plinth for the motor as well as some new footers for the motor. Those were supplied by Dan at Eden sound. These resulted in a significant improvement; I would say about 95% of the hum was gone.
I wanted to try to further diminish or completely eliminate the hum. When I had my SDS set to 45 RPM, I did not hear any noise, and the motor did not vibrate when I placed my finger on it. However, when the speed was set to 33 RPM, there was palpable vibration of the motor as well as an audible hum coming from the motor even when the stylus was not in the groove.
So, I tried a few things. First of all, I had my SDS plugged into my power conditioner. I unplugged it and plugged it into the wall. That did not make much difference. However, I did notice less noise at the initial ramp up voltage of 115 V when the SDS was used. When the voltage droped down to 72 V, the hum returned. Then, I plugged my turntable motor directly into the wall. This did decrease the noise quite a bit. Finally, I unscrewed and removed the stock footers on the bottom of the motor. Until then, I had left them in place and attached the new footers beside them; both sets of footers were in contact with the plinth. (I know I should have removed the original set before, but I thought they were stuck on and didn't want to damage the motor housing.) Then, the motor sat only on the new footers which I had gotten from Eden sound. As I noted previously these were on top of the custom made Terrastone plinth. Removing the stock footers cured the problem. Now when I place my fingers on the motor I no longer feel any vibration. When I am standing close to the turntable I no longer hear any hum. And I no longer hear a hum coming through my speakers at the end of the record.
I was going to try to calibrate my SDS so that I could increase the baseline voltage. However, now that I have eliminated the noise and vibration with the footer tweak, I will leave the SDS as it is. However I am going to keep it plugged into the wall rather than into the power conditioner. I also have a Terrastone platform coming for my turntable to sit on. At the moment it is on a 3 inch thick maple butcher block with the turntable on Terracone footers from Eden sound. I know there are lots of threads on various forums about the hum issues with the VPI motor. I have been reading those and was thinking I might have to replace a capacitor or do something more significant with the motor. However, the simple maneuver of removing the stock footers did the trick. That of course is in addition to the significant improvement that was already attributable to the new motor plinth and footers for the turntable. I know this was frustrating for me so I hope that my experience might help some of you out there who have been trying to deal with a similar problem.
I do realize that there are various causes for a hum in these motors. It can be electrical or mechanical in origin. In this case it was primarily mechanical, although the input voltage had an effect. I'm sure there are other products that could be used to deal with the vibration which would work well also. I have been very happy with the products I have gotten from Dan Sherbrook at Eden sound. My purpose here is not to plug his product but to provide information that I wish I had had several months ago when I started dealing with this.