Though speed stability is very important (who wants wow?), in my opinion, what is really needed is voltage reduction to minimize the synchronous pulse noise from the motor.
I use a $60 Variac on an original VPI Aries. I start the table on 120v. I use that voltage for light record cleaning, finishing with a carbon fiber brush. Then I reduce the voltage to around 60 - 65v for playback. That's plenty of voltage for the VPI motor, and that voltage level reduces the intensity of the synchronous motor pulses significantly.
Once the speed of the table is established and locked on the ~ 60hz "grid" frequency, the table does not experience audible speed fluctuation. At least, I don't hear speed fluctuation. But if line-related noise is important, reducing the voltage in half will also cut the line-related noise in half. That voltage reduction makes a quite audible improvement.
IMO, the synchronous motor pulse noise is magnitudes greater than line-related noise, but I admit never attempting to measure it.
The SDS provides a similar voltage reduction though not as extreme as I use. There is also the same kind of signal regeneration as the Phoenix units. The SDS is more expensive than the Eagle / Roadrunner but includes voltage reduction where it appears the Phoenix products do not.
I have not tried a SDS unit in my system, but friends use it with very good results.
I have no familiarity with the Walker unit.
I use a $60 Variac on an original VPI Aries. I start the table on 120v. I use that voltage for light record cleaning, finishing with a carbon fiber brush. Then I reduce the voltage to around 60 - 65v for playback. That's plenty of voltage for the VPI motor, and that voltage level reduces the intensity of the synchronous motor pulses significantly.
Once the speed of the table is established and locked on the ~ 60hz "grid" frequency, the table does not experience audible speed fluctuation. At least, I don't hear speed fluctuation. But if line-related noise is important, reducing the voltage in half will also cut the line-related noise in half. That voltage reduction makes a quite audible improvement.
IMO, the synchronous motor pulse noise is magnitudes greater than line-related noise, but I admit never attempting to measure it.
The SDS provides a similar voltage reduction though not as extreme as I use. There is also the same kind of signal regeneration as the Phoenix units. The SDS is more expensive than the Eagle / Roadrunner but includes voltage reduction where it appears the Phoenix products do not.
I have not tried a SDS unit in my system, but friends use it with very good results.
I have no familiarity with the Walker unit.