For Basis TT owners does the VPI SDS work?

How much of a benefit is a power supply that does not eliminate the phase splitting cap in the motor, and instead, supply two separate phases to the motor?

The Basis approach, which involves modifying the motor and eliminating the phase splitting cap, make much more sense to me.

Also, how would the other power supplies work for changing speed? Since the motor is a synchonous motor, that would mean it generates a different frequency ac power for 45 rpm. Wouldn't the ideal phase splitting capacitor be different for the different frequency of ac being supplied?

A single-phase AC controller would still work to control speed of a synchronous motor. Proof of that is the fact that the Walker and SDS controllers do work with all such motors. But you are correct that a controller that could supply two sine waves that were 90 degrees out of phase would be more ideal in terms of noise reduction (and cogging, I think). The Basis unit looks nifty but it costs quite a bit. I see where Allnic has a tube-based controller, also very expensive.

Lewm,

Yes, one can generate a different AC frequency to drive the motor at a higher speed. But, what I am wondering is whether a capacitor "tuned" to 60Hz can effectively create the 90 degree offset phase. If not, the owner would be better off using the controller at the 33.33 rpm speed setting while moving the belt on the pully to achieve 45 rpm.

While I'm sure the Allnic unit has many tubes and nickel-core transformers enclosed in a shiny fascia (I believe Brinkman has a similar device), this is by no means a guarantor of accurate motor control - personally, I'd prefer a substantial number of integrated circuits to be at the heart of my motor controller. Synthesis and control of discrete sine waves for motor control applications is a delicate task requiring a high degree of repeatable accuracy best performed digitally with an analog amplification stage. A phase shift cap is a crude attempt at best...

-Richard

Das

I bought a VPI SDS 7 days ago and think it's worth it. I used a Clearaudio Strobe Disc and Strobe Laser to adjust the speeds it was amazing how far off the speeds were. There was a different feeling to the music when played at the correct speed, it seemed more "solid/powerful" it just felt right. When I installed the SDS I was using a Koetsu Rosewood and it did tighten up the base some and clean up the highs a little. Yesterday I switched carts to a Koetsu Urushi Black granted this is a big improvement( much more extended, dynamic with much better inner detail) it should expose any problems but the sound stayed clear, powerful and smooth. Now I don't think you can feel that correctness without some type of speed control(just my guess). I'm not ready to A-B with/without the SDS yet as I'm enjoying just listening, 7 hours today!!!