speed stability

+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. .

Wynnosu, I'm not sure where you live that you would need protection for your equipment. The PS Audio regenerators are sold for cleaning your ac and in theory making your system sounding better. In my experience with the PSA along with quite a few other regenerators the opposite was true. Hence my comment regarding the PSA. Also all regenerators dump a lot of noise back in the lines and you have your amp plugged in that line. Of course depending on the equipment and location your mileage might vary. Interestingly I am testing a new regenerator that is showing potential and might be the exception to the rule.

Hi Benjie, I never said that SDS or other speed controllers don't affect sound, of course they do. A stable speed with the correct pitch will have a positive effect on sound. And I agree that motor induced vibrations can have negative sonic effects. My comment was about reducing motor vibrations by dropping voltage. What are they dropping the voltage to? Does the SDS ramp up to over voltage and then drop down to the correct voltage or does it drop down to some nominal voltage like 40 volts?

Don't know about your TNT but none of my tt motors will work properly with significantly lowered voltage.

Dkarmell-

The SDS will drop the voltage to as low as possible to maintain the necessary speed and frequency (user controlled). It does have a minimum specification is always reached: 72volt, if the motor is working properly.

You can see the unit change upon start up from 115V to the 72 volts at 33 rpm. At 45 rpm the voltage is 83V as I recall.

The user has no control over voltage, just frequency - which is set to a strobe such as KAB's.