The TechDas Airforce Zero, utilising a 3-phase motor, actually has a 3-phase controller and three 50W power amplifiers (one per phase) to drive the motor!
As you pointed out my Final uses both a sine and cosine wave generator preamplifier feeding a stereo power amp to drive the motor. As well as infinite speed adjustment on both speeds independently it has the provision to continuously vary the amount of torque supplied to the motor.
Originally it used Stax D80 monos to drive the motor, but since then I’ve used Bryston monos (custom) , Rowlands - each amplifier imparts its own sound. Currently I use an Onix Audio OA60 to drive the motor - it has a fully regulated power supply internally. Importantly because you are amplifying sine/cosine waves cables make a huge difference. I am using MIT Oracle interconnects and speaker cables in the wiring loom from controller to power amp to motor for my TT motor supply. The phase coherency superiority of these cables in the TT power supply are quite audible.

