Here is some useful information about the Platine Verdier motor (J.C.Verdier, The Manufacturers’ corner, SOUND PRACTICES - Issue 11):
"... First of all, let’s approach the question of the motor. Certainly, I use a motor marked Philips, a name that could make one think of an ordinary motor, because that big European trademark is very prominent in the mass market for consumer goods.
That is misleading, because Philips is also very involved in very advanced technology. The motor used in the Platine Verdier is produced by a special branch named "Philips Technology". The motor is certainly not an ordinary part - given that the price is 2500 FF for one unit in the shop of the the French distributor! That is not exactly a gift for a motor of diameter 40mm and 50mm high. It must have something very special inside. Let us see:
First af all, it is "low inertia" motor. In the case of Philips unit, that term refers to a very special technology. In "low inertia" motor, the turning part-the rotor-consist of a cooper coil, the turns almost parallel to the rotation axle cutting the field lines of the magnetic circuit, excited by a permanent magnet which is totally fixed. The weight of the rotor is reduced as much as possible, so the inertial tendency is small relative to the work provided by the motor.
I must say that I don’t think that low inertia in itself is that interesting of a quality for turntable’s motor. It can even be a deficiency for players with relatively light platters, as indicated in my discussion of the value of mechanical braking below.
Another quality of the low inertia motor is much more interesting and relevant to the issue at hand: its rotation speed depends directly on the DC voltage. A simple integrated circuit regulator such as an LM 338 is enough to obtain perfect stability of the speed.
Let us come back to the motor description: The magnets are very powerful in a small package. They are metallic alloy (nothing like cheap ceramic magnets). The collector and the brushes are gold plated to minimize the resistance of the contacts.
The axle of the motor turns in fitted and self lubricated bronze bearings, its diameter is 3mm. When the motor is powered at its nominal voltage of 12V, we hear the rubbing of the brushes on the collector. It requires a very small environment to be able to hear this small noise.
In the Platine Verdier, the actual voltage applied to the motor is 3V for 33 RPM and 4V for 45 RPM. At those low voltages, it is necessary to pres your ear directly on the motor to hear the commutation sound..."
