Jerome: could you clarify this statement: "Whenever turntable motors are stopped, there is a need to power off the mains feeding the motors, and turning it on again."
By powering off the mains, you mean at the breaker? Disconnecting the AC cord from the receptacle?
Shutting off the motor, at least for me, is turning off the power to the motors from the controller. But I read your statement, if you are serious, to mean something more....
Bill
Every time the motor is stopped (to change sides or to change LP altogether), the power supply to the motor must be disconnected first, then connected on again. The sonic differences, as a result of "refreshing" the motor is very audible in many systems I tried, regardless of whether the turntable motor is fed direct from the wall, or fed from a speed controller device.
In fact I first discovered it while fiddling with a speed controller device on a friend's system.
I discovered that LP playback sound becomes forward, muddied, bass bloated (some people might like this actually) when the speed control unit was changed from 33rpm to 45rpm, then back to 33rpm again. We were just putting another record on (that we played just not ago) when we unwittingly changed the speed, and we noticed the sonic differences straight away.
On a hunch, I disconnected the power supply to the speed controller unit (scu) and found that the "refreshed" scu makes the turntable/LP sounds more opened, more detailed, more dynamic, more musical all at the same time. Btw, the power supply cord between the speed controller to the motor is hardwired, so the only way to refresh the motor is switching off power supply to the speed controller.
Later, myself, and a few other listeners repeated the test with several other different LPs and on different turntable models, and found the sonic results repeatable and consistently audible, without straining to hear it. Later I discovered the same thing at home with my Michel Gyro se, which works without a scu, and in other people's systems, with several other turntables, also without scu.
Luckily my gyro se turntable motor is driven by a separate ac line from the wall (within easy reach of my left hand) away from the dedicated ac line feeding the pre and phonostage, which is behind the equipment. every time I stop the turntable, for whatever reasons, I just need to refresh the ac (by turning off and turning on again) feeding the motor to consistently get the level of dynamics and clarity that i didnt know this turntable is capable of. It is like I got a $$$$ upgrade to my gyro se!