Originally Posted by Class A
Not a placebo effect. The difference is not like your hearing Alvin & the Chipmunks and normal voices. You'll usually get a tighter bass and more realistic piano. A few weeks ago w/a few other audio guys I know were working on a 12yr old VPI TT. The motor alone weighed about 20lbs. It really sounded excellent. One of the guys added a Walker Audio speed controller and it picked up the sound quality quite a few notches. Tighter bass, more bite on the guitar and a deeper soundstage. Now the VPI did sound nice w/out the Walker add on but the addition of the controller took it to another level. Remember a motor on a $399 TT is not going to be 100% accurate. A little help from a decent speed box will pick improve the sound.
Agreed, it's not a placebo effect as many can hear the difference (present company included), and there is solid reasoning for the improvement in sound by using a speed box.
I have yet to see anyone give an explanation of how the "speed box" units work. While they do allow you to change the speed, the real work that these units do is generate a new 60Hz signal
. For the synchronous AC motors that many belt drive turntables use, the frequency of the incoming AC power, and the number of poles in the motor, are what determine the motor's speed, not the voltage. That 60Hz we receive from the utility company is a nominal value, and that is definitely not a "clean" sine wave! All sorts of crud comes over our power lines, and we're feeding that crud into a simple AC motor that knows no better than to follow whatever type of power is fed to it.
These speed control units generate a new, dead-accurate, quartz controlled, and very clean 60Hz power output to feed to the motor. To "magically" change the speed to 45RPM, the speed box simply switches to a higher output frequency.
Is a motor in a cheaper turntable any less "accurate" than in an expensive 'table? Not necessarily. Simple fact is, AC motors rotate at a speed based on the incoming line frequency and the number of "poles" in the motor. Discrepancies in final rotation speed of the turntable platter may come from an improper pulley size, a slipping belt, drag on the motor or spindle bearings, an out-of-balance platter, or (on much smaller scale) the "crud" coming off the power line. Better AC motors will indeed run smoother
than cheaper ones, through better materials and build tolerances used to manufacture the motor (especially the bearings used). Another factor in smoothing out speed variations is the weight of the rotating mass (the mass of the platter, subplatter and spindle); a heavier platter creates a larger flywheel effect, whereas a lighter platter will be more susceptible to variations in speed.