speed stability

Benjie, SDS & PSA are exactly the same thing, both are digital regenerators! The only difference might be that the SDS will allow finer tuning of frequency adjustment to control speed of synchronous motors. I'm not familiar with the current ones but earlier PS Audion units did have a certain amount of frequency control too.

"By reducing the voltage to the tt motor, the motor produces less vibration and makes a significant improvement in sound reproduction. Hey, we all know that less vibration to a turntable means better sound. The SDS is a truly amazing piece of electronics." This is completely false and is in the same moronic category of using expensive power cords on tt motors and claiming it improves sound quality. There's nothing amazing or revolutionary here, the SDS is just another AC regenerator and at the 2k price there are plenty of more featured industrial units around. Only the interface is audio specific.

Elizabeth, a steady 60hz cycle doesn't guarantee the correct speed of your tt. A frequency controller is a pitch/speed control for synchronous motors and allows one to set the correct frequency to achieve the right pitch for 33/45/78 rpm if your table is setup for it, not every table will give you all 3 speeds. Servo controlled motors, direct or belt driven aren't the most accurate and further servo control has negative impact on sound quality while continuously tweaking the speed.

Lewm, tweaking the frequency slightly above or below 60hz has no effect on electronics, just motors. In general you really shouldn't use a regenerator with your electronics because of the negative impact they have on sound quality. Some manufacturers do advise against using any regenerator with switching power supplies, irrespective of frequency control.

I used a PS Audio P300 to power the motor of a VPI Scout in the past. My experience is exactly summarized by Dkarmeli's post above. While it didn't provide the finer increments of frequency tuning the SDS did, it was good enough in my case. I heard no deleterious effects on preamp and cd player (also powered by the P300) by altering frequency 1-2 hz.

Thanks to everyone fir their input.

Dkarmeli: I had question about you comment regarding using electronics through a power regenerator. I originally purchased the PS Audio piece to protect the preamp, cd player, turntable, tuner, etc.

I knew it didn't have the ooomph to protect my Audio Research VT200, but I assumed the other components would be more stable as well as protected by the regenerator. Watching the scope on the PS Audio, I can see how much better the THD is as well as the voltage. But I had never heard that using such a device can be deleterious to the sound.

What is the reason for this? Thanks in advance.

+1 Benjie. The SDS definitely does make a difference. I recently had to remove it from my system to have it serviced in the middle of a listening session, and although the speed of my Classic was still incredibly stable and accurate without the SDS, the sound lacked the transparency and the background quietness (transparency most likely affected by the decreased blackness of the background) I had with the SDS powering the turntable. My brain adjusted to the sound after a few days, but the decreased voltage allowed by the use of the SDS and reduction in vibration does result in a quieter table and ultimately better sound. .