VPI Analog Drive System: An Update of VPI's Renowned SDS Motor Drive System Provides Dramatically Natural Musical Presentations
The VPI Analog Drive System, or ADS, is a high-tech speed-selection device for 33 1/3 and 45RPM LP playback. Free of digitally based electronics, the extraordinary-sounding ADS represents an evolution of the function embodied by VPI's SDS (Synchronous Drive System) and an entirely original way at looking at the speed controller concept. Audibly superior to SDS, ADS represents VPI's biggest non-turntable breakthrough in the 21st century and brings bold, across-the-board enhancements to the performance of almost any turntable. If your 'table uses an AC Synchronous motor that draws less than 10 watts, you owe it to yourself – and your analog setup and vinyl – to audition this new motor controller. Simply plug your rig into ADS and hear the improvements a truly powerful motor drive creates: Deeper bass, smoother midrange, sweeter highs, lower noise floor, deeper imaging, airier top end, and reach-out-and-touch-it solidity. (Important note: VPI ADS is NOT compatible with turntables that have an outboard or wall-wart power supply. If you cannot directly connect an IEC power cord to your VPI 'table, ADS will not work.)
When compared to its predecessor, ADS presents a smoother, more coherent presentation on complex passages with unparalleled focus and stability. The biggest difference is the generation an extremely low-distortion analog sine wave – relative to the digitally synthesized circuits of SDS. Regenerating the AC sine wave eliminates the power-line noise and harmonics, providing pure, smooth AC power to the turntable motor. The unfiltered speed accuracy of ADS is measured at +/- 0.01Hz / .003%. In other words, its accuracy remains without peer. Coupled with the higher-current drive circuitry, ADS creates a sense of ease and purity on every record which is especially noticeable on dynamic passages. It also delivers outstandingly precise calibration of platter speed with rotary dials for very fine adjustments of both 33RPM and 45RPM settings. ADS truly "dials-in" the performance of almost any turntable.
ADS' Platter Power Ramp feature applies full power to the platter for eight seconds once start is pressed, allowing even the heaviest platters to come quickly up to speed. The power to the motor is then ramped down to 90 VAC to provide an optimum balance between motor torque and power dissipation. When the motor drive is idle, it cycles into a low power dissipation mode.
We are often asked by SDS owners if it makes sense to upgrade to ADS. The answer: A resounding YES! But don't take our word for it. Audition ADS in your system and on your VPI 'table (or most other 'tables, for that matter). If you own a VPI 'table or another make – even if you own an SDS – ADS will seriously change your life for the better. Then, tell us your impressions. You have Music Direct's Money-Back Guarantee that ADS will live a happy life powering your motor and taking complete control of the speed accuracy of your turntable.
"I was simply blown away when auditioning the ADS versus the SDS. It is noticeably quieter and so much smoother during playback. I personally prefer analog, and there is no digital in this new design. In rigorous testing, our analog oscillators maintain their set-point over weeks without drift, with measurement resolution of +/-0.01Hz / .0003%. In other words, dead-on-accurate. The sine wave produced by the ADS is perfect, the noise level is extremely low, the drive current is very powerful. It has brought my personal Avenger one step closer to my Ampex ATR-102 reel-to-reel machine."
– Harry Weisfeld, founder, VPI Industries
ADS' Technical Details in a Nutshell
In technical terms, ADS hits a grand slam. Whereas SDS has a switching power supply, ADS employs a high-current linear power supply to provide the precise voltage and high current required by the motor drive amplifier. In addition, simple and extremely reliable analog circuitry performs the run/stop and speed-selection duties. A powerful Class A/B amplifier provides the drive for the motor. And separate 33 and 45RPM oscillator controls adjust the speed with a center detent position factory calibrated to exactly 60/81Hz (33/45 RPM). With a strobe disc, any necessary speed adjustments can be quickly and easily implemented.
Analog Frequency Reference Oscillators and Remarkably Low Distortion
ADS' prodigious abilities relate to its Analog Frequency Reference Oscillators. The analog-based oscillators are high-quality adaptations of vintage Instrumentation oscillator designs, implemented with top-grade parts embedded in a meticulously designed circuit. The turntable drive motor is now driven by a regenerated, low-distortion sine wave, free of the noise and distortion that accompanies the raw AC power supplied to stereo systems. Relative to the digitally based SDS, the audible benefits of generating an extremely low-distortion analog sine wave relative to digitally synthesized signal simply cannot be captured in words. The sonic differences are that great.
Powerful Motor Drive Amplifier Responds to the Exact Demands of the Motor
The drag of a stylus through a blank groove presents a constant demand to the power supply, albeit a negligible one. However, once the music starts everything changes, the drag of the stylus creates a complex ever-changing dynamic demand on the power supply. The more challenging the material, the harder the power supply has to work to provide current to the motor. ADS' Motor Drive is a high-current, servo-controlled Class AB amplifier designed specifically to track and respond to any demands placed on it by the motor. A well-designed motor drive amplifier with a surplus of reserve power provides plenty of motor torque for steady platter rotation regardless of the dynamic conditions presented by the record. Focus, drive, clarity, and resolution exponentially increase. The improvements ADS provides are readily heard in comparison to the SDS or when listening to familiar recordings.
The ADS Power Supply
While SDS utilized a Switched Mode Power Supply (SMPS), ADS employs a high-current linear power supply to deliver the voltages and currents required by the motor drive amplifier, with an additional regulated power supply for the control logic.
