Hi phoenixengr. why do you think VPI use trapezoidal commutation?
Surely this is not optimum if they want to minimize torque ripple.
Cheers
Surely this is not optimum if they want to minimize torque ripple.
Cheers
Stylus-Drag..Fact or Fiction?
Hi phoenixengr. why do you think VPI use trapezoidal commutation? Surely this is not optimum if they want to minimize torque ripple. Cheers |
"....why do you think VPI use trapezoidal commutation? The controller is made by Elmo Motion Control (Gold Twitter Solo), and while Elmo's PC control software is fairly comprehensive, I'm not sure if the controller is capable of sinewave drive; it is not capable of sensorless operation (FOC) which would use sinewaves. Sinewave drive is considerably more complicated and would result in smoother operation, but for whatever reason, VPI chose to operate the motor in the simplest mode available, as a DC motor which uses block commutation and Hall sensors. They do some other rather strange things: The motor is designed for high power (500W) so the windings are 0.3R; not the easiest load to drive especially from a class AB output amp. The Elmo controller uses PWM output at 10kHz, which IMHO is a bad choice for use around a sensitive audio circuit like a cartridge pickup (especially MM). |
Unfortunately, I haven’t had the chance to "look under the hood" on very many of them, but based on my limited exposure: Belt drive: American Sounds AS2000. David Karmeli not only understands high end audio, he gets the physics and engineering part right as well. His design philosophy may be unique in the industry. Full disclosure: I had a hand in designing the motor control for this table, based on the Eagle PSU and RR tach. Direct Drive: I’ve not auditioned the new Technics tables and I don’t have a lot of technical info on them, but from what I can gather, they are doing some really sophisticated things in motor control and they have the engineering HP to do things right. It wouldn’t surprise me at all if they were doing FOC. I’m basing my observations more on an engineering perspective than an audiophile one. YMMV. |