Pro-ject speedbox: Is improvement worth the $ ?

The Speed Box only provides the user to change speeds at the push of a
button. It does not have the ability to fine tune the speed to compensate for
deviations in pulley, platter, and belt tolerance.

Since your motor is an AC synchronous motor, it is not dependent on stable
ac voltage like a dc motor but relies on the grid's 60 hz frequency.
Fortunately in the US, the 60hz frequency is highly regulated and controlled
and does not deviate like line voltage. A true motor controller will have the
ability to change the frequency thus allowing a fine tune of the motor's
speed.

I wouldn't purchase a Speed Box unless I frequently changed between 33
and 45 records. Spend your money on a real motor controller, not a switch
box.

Zd542, the project's motor is an ac sychronous and is not dependent on
stable voltage as the speed is determined my the line frequency. As
previously stated, the 60hz US standard is highly regulated and monitored
and does have the same swing variance as does voltage.

The older PS Power Plants had the ability to both regenerate the ac voltage
and change the line frequency, therefore, they could be used as ac motor
controller, but their line frequency adjustment was too course for fine
adjustments. Both the Walker and VPI's SDS are good examples of a
successful implementation of an ac motor controller.

BTW, voltage regulators (good ones like Furman) do provide 120v stable
voltage. You don not need a power regenerator to produce stable voltage.