About Synchronous Drive System (SDS) Motor Drive by VPI:
The Synchronous Drive System (SDS) combines a turntable motor speed controller and a line isolator into one convenient 16" x 3" x 12" (W x H x D) package. The SDS breaks new ground in clean accurate power delivery using advanced digital technology and quartz crystal accuracy.
The SDS allows for the adjustment of both the voltage and frequency fed to the turntable motor. Adjustments are easily made from the front panel using intuitive, soft touch controls. The selected output voltage and frequency are shown using large, easy to read LED displays. The SDS slowly ramps the voltage and frequency up or down to the selected value in order to prevent premature motor wear due to abrupt changes. During motor startup, the SDS increases its output voltage in order to bring the platter up to speed quickly. Once the desired platter speed has been reached, the SDS ramps the output voltage down in order to reduce motor vibration and, therefore, the systems noise floor.
The circuit used in the SDS provides an incredibly accurate line frequency of great stability. Additionally, the electronic circuitry effectively isolates the output voltage from the input voltage, doing away with voltage spikes, low level fluctuations, RFI, and frequency variations.
Instead of merely filtering the power line, the SDS first changes it into pure DC voltage and then digitally regenerates its own clean signal. This approach is superior to that used in many of the other power line conditioners on the market.
The SDS works best with synchronous motor driven 115 volt turntables, such as those from VPI. The speed of a synchronous motor is determined by the frequency it is fed. It is only logical then, that a device whose speed is based on the line frequency will always function better when a stable frequency is delivered. A constant motor speed translates into a quieter, more faithful musical presentation.
COLLECTORS ALERT: Many historical recordings were not transferred onto modern records at the proper speed. Using the SDS, you can now correct the musical pitch of these recordings by varying the speed of your turntable. In addition, collectors who have VPI turntables that run at 78 RPM will be able to accurately adjust them to compensate for the wide variation in recording speed used in the 78 RPM era.
The SDS is the perfect match for all 115 volt VPI turntables!