Stylus Drag

Aoliviero -
I can only surmise that the power supply and feedback mechanism of the Raven AC is inadequate if it cannot hold the speed. I certainly wouldn't be happy spending that sort of money on a TT and it not being able to hold the speed accurately whilst playing. Have you asked the manufacturer ?

Even in a closed loop system some speed variation will occur. An error must exist between the setpoint and actual before the system will react. A certain deadband around the setpoint exists or else the sytsem would hunt, ie. cycle about the setpont which would be much worse. That is the theory. I do not know the details of the actual tt design. It is analogous to the cruise control on your car. You are at a set speed and come to a hill. Notice the speed drops one or two mph as the engine increases torque to compensate. The same happens as you go down a hill; the speed increases one or two mph as the engine torque decreases. But in the case of our high end turntables, I think the designers have the platter speed held to within 2 decimal places under moderate load variations due to needle drag.

Where is the feedback mechanism in a Raven turntable?

Bottom line is measuring rotation speed is not rocket science. ANyone who is in question how well their table maintains proper speed should be able to measure and confirm as needed and put the issue to rest.

"How does one measure "rhythm and pace" again? That is totally subjective, which is fine if that works for you but has no real meaning or use to others accordingly.

I'd be willing to bet that practically imperfections in record manufacturing, warping over the years, etc. is a much bigger real issue than stylus drag with most any well designed and executed turntable. Of course, we have little control over that, so probably more practical to fret the details of stylus drag assuming those who created our SOTA turntables did not?

My records sound fantastic, so I see little value for me personally.

In any motor, AC or DC, if the load increases the current in the motor will increase too. This provides a feedback mechanism that functions well even on open loop systems. For an AC motor that runs off the line, if the motor has any torque at all it will be able to compensate for stylus drag with ease (the voltage of the AC line contributes to torque while the frequency determines the speed) as it might just draw a little more current to stay on speed and with the AC line, there is essentially an infinite supply.

With a DC motor (open loop- not sure if that is the right term as many DC motors have internal electro-mechanical speed controls) the limitation *can* be the stability of the power supply. There are a lot of variables here depending on design so calling out generalizations can be risky.