VPI ADS and SDS Users, Swap Out Your Pulley For A Solid Improvement
The HRX Pulley should be considered a must-have for any VPI turntable owner who uses an ADS or an SDS. The HRX pulley is a single speed pulley, which when used with an ADS or SDS provides a substantial sonic improvement over the stock two-speed pulley which comes standard on most VPI tables. Replacement is simple, using an allen wrench, remove the old pulley and install the HRX Pulley, shouldn't take more than a few minutes. The transformation offers impressive improvements in tonal balance, image stability and overall resolution. We find it astonishing that such a relatively inexpensive upgrade can pay such large dividends in musical enjoyment and we think you will too.
To understand why the HRX Pulley makes such an improvement, it's important to understand more about the standard 33/45 RPM Pulley. The stock pulley requires two machining steps during production. The first step creates the larger pulley section (45RPM), the second creates the smaller section (33RPM). During the transition between machining these the two steps, very small inaccuracies creep into the process. These inaccuracies would only be noticeable with a micrometer, and on VPI tables not using an ADS or an SDS, these imperfections are inaudible.
The greater motor precision offered by VPI's outboard motor controllers (ADS & SDS) means higher performance is now attainable and desirable. The HRX pulley is machined for a single speed (45RPM) allowing much tighter tolerances and greater dimensional accuracy. This is also why the HRX pulley can only be used on VPI turntables which have an ADS or SDS motor controller, without one of those devices to select the platter speed, the turntable would only spin at 45RPM.